belongs to Maven artifact com.android.support:recyclerview-v7:28.0.0-alpha1
RecyclerView.LayoutManager
public
static
abstract
class
RecyclerView.LayoutManager
extends Object
java.lang.Object | |
↳ | android.support.v7.widget.RecyclerView.LayoutManager |
Known Direct Subclasses |
Known Indirect Subclasses |
A LayoutManager
is responsible for measuring and positioning item views
within a RecyclerView
as well as determining the policy for when to recycle
item views that are no longer visible to the user. By changing the LayoutManager
a RecyclerView
can be used to implement a standard vertically scrolling list,
a uniform grid, staggered grids, horizontally scrolling collections and more. Several stock
layout managers are provided for general use.
Context
, AttributeSet
, int
, int
), RecyclerView will
instantiate and set the LayoutManager when being inflated. Most used properties can
be then obtained from getProperties(Context, AttributeSet, int, int)
. In case
a LayoutManager specifies both constructors, the non-default constructor will take
precedence.
Summary
Nested classes | |
---|---|
interface |
RecyclerView.LayoutManager.LayoutPrefetchRegistry
Interface for LayoutManagers to request items to be prefetched, based on position, with specified distance from viewport, which indicates priority. |
class |
RecyclerView.LayoutManager.Properties
Some general properties that a LayoutManager may want to use. |
XML attributes | |
---|---|
RecyclerView_android_orientation |
|
RecyclerView_reverseLayout |
|
RecyclerView_spanCount |
|
RecyclerView_stackFromEnd |
Public constructors | |
---|---|
RecyclerView.LayoutManager()
|
Public methods | |
---|---|
void
|
addDisappearingView(View child, int index)
To be called only during |
void
|
addDisappearingView(View child)
To be called only during |
void
|
addView(View child, int index)
Add a view to the currently attached RecyclerView if needed. |
void
|
addView(View child)
Add a view to the currently attached RecyclerView if needed. |
void
|
assertInLayoutOrScroll(String message)
Checks if RecyclerView is in the middle of a layout or scroll and throws an
|
void
|
assertNotInLayoutOrScroll(String message)
Checks if RecyclerView is in the middle of a layout or scroll and throws an
|
void
|
attachView(View child)
Reattach a previously |
void
|
attachView(View child, int index)
Reattach a previously |
void
|
attachView(View child, int index, RecyclerView.LayoutParams lp)
Reattach a previously |
void
|
calculateItemDecorationsForChild(View child, Rect outRect)
Calculates the item decor insets applied to the given child and updates the provided Rect instance with the inset values. |
boolean
|
canScrollHorizontally()
Query if horizontal scrolling is currently supported. |
boolean
|
canScrollVertically()
Query if vertical scrolling is currently supported. |
boolean
|
checkLayoutParams(RecyclerView.LayoutParams lp)
Determines the validity of the supplied LayoutParams object. |
static
int
|
chooseSize(int spec, int desired, int min)
Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec. |
void
|
collectAdjacentPrefetchPositions(int dx, int dy, RecyclerView.State state, RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)
Gather all positions from the LayoutManager to be prefetched, given specified momentum. |
void
|
collectInitialPrefetchPositions(int adapterItemCount, RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)
Gather all positions from the LayoutManager to be prefetched in preperation for its RecyclerView to come on screen, due to the movement of another, containing RecyclerView. |
int
|
computeHorizontalScrollExtent(RecyclerView.State state)
Override this method if you want to support scroll bars. |
int
|
computeHorizontalScrollOffset(RecyclerView.State state)
Override this method if you want to support scroll bars. |
int
|
computeHorizontalScrollRange(RecyclerView.State state)
Override this method if you want to support scroll bars. |
int
|
computeVerticalScrollExtent(RecyclerView.State state)
Override this method if you want to support scroll bars. |
int
|
computeVerticalScrollOffset(RecyclerView.State state)
Override this method if you want to support scroll bars. |
int
|
computeVerticalScrollRange(RecyclerView.State state)
Override this method if you want to support scroll bars. |
void
|
detachAndScrapAttachedViews(RecyclerView.Recycler recycler)
Temporarily detach and scrap all currently attached child views. |
void
|
detachAndScrapView(View child, RecyclerView.Recycler recycler)
Detach a child view and add it to a |
void
|
detachAndScrapViewAt(int index, RecyclerView.Recycler recycler)
Detach a child view and add it to a |
void
|
detachView(View child)
Temporarily detach a child view. |
void
|
detachViewAt(int index)
Temporarily detach a child view. |
void
|
endAnimation(View view)
Ends all animations on the view created by the |
View
|
findContainingItemView(View view)
Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager. |
View
|
findViewByPosition(int position)
Finds the view which represents the given adapter position. |
abstract
RecyclerView.LayoutParams
|
generateDefaultLayoutParams()
Create a default |
RecyclerView.LayoutParams
|
generateLayoutParams(Context c, AttributeSet attrs)
Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource. |
RecyclerView.LayoutParams
|
generateLayoutParams(ViewGroup.LayoutParams lp)
Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible. |
int
|
getBaseline()
Returns offset of the RecyclerView's text baseline from the its top boundary. |
int
|
getBottomDecorationHeight(View child)
Returns the total height of item decorations applied to child's bottom. |
View
|
getChildAt(int index)
Return the child view at the given index |
int
|
getChildCount()
Return the current number of child views attached to the parent RecyclerView. |
static
int
|
getChildMeasureSpec(int parentSize, int parentMode, int padding, int childDimension, boolean canScroll)
Calculate a MeasureSpec value for measuring a child view in one dimension. |
static
int
|
getChildMeasureSpec(int parentSize, int padding, int childDimension, boolean canScroll)
This method was deprecated
in API level 24.1.0.
use |
boolean
|
getClipToPadding()
Check if the RecyclerView is configured to clip child views to its padding. |
int
|
getColumnCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the number of columns for accessibility. |
int
|
getDecoratedBottom(View child)
Returns the bottom edge of the given child view within its parent, offset by any applied
|
void
|
getDecoratedBoundsWithMargins(View view, Rect outBounds)
Returns the bounds of the view including its decoration and margins. |
int
|
getDecoratedLeft(View child)
Returns the left edge of the given child view within its parent, offset by any applied
|
int
|
getDecoratedMeasuredHeight(View child)
Returns the measured height of the given child, plus the additional size of
any insets applied by |
int
|
getDecoratedMeasuredWidth(View child)
Returns the measured width of the given child, plus the additional size of
any insets applied by |
int
|
getDecoratedRight(View child)
Returns the right edge of the given child view within its parent, offset by any applied
|
int
|
getDecoratedTop(View child)
Returns the top edge of the given child view within its parent, offset by any applied
|
View
|
getFocusedChild()
Returns the item View which has or contains focus. |
int
|
getHeight()
Returns the height that is currently relevant to the LayoutManager. |
int
|
getHeightMode()
Return the height measurement spec mode that is currently relevant to the LayoutManager. |
int
|
getItemCount()
Returns the number of items in the adapter bound to the parent RecyclerView. |
int
|
getItemViewType(View view)
Returns the View type defined by the adapter. |
int
|
getLayoutDirection()
Returns the resolved layout direction for this RecyclerView. |
int
|
getLeftDecorationWidth(View child)
Returns the total width of item decorations applied to child's left. |
int
|
getMinimumHeight()
|
int
|
getMinimumWidth()
|
int
|
getPaddingBottom()
Return the bottom padding of the parent RecyclerView |
int
|
getPaddingEnd()
Return the end padding of the parent RecyclerView |
int
|
getPaddingLeft()
Return the left padding of the parent RecyclerView |
int
|
getPaddingRight()
Return the right padding of the parent RecyclerView |
int
|
getPaddingStart()
Return the start padding of the parent RecyclerView |
int
|
getPaddingTop()
Return the top padding of the parent RecyclerView |
int
|
getPosition(View view)
Returns the adapter position of the item represented by the given View. |
static
RecyclerView.LayoutManager.Properties
|
getProperties(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
Parse the xml attributes to get the most common properties used by layout managers. |
int
|
getRightDecorationWidth(View child)
Returns the total width of item decorations applied to child's right. |
int
|
getRowCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the number of rows for accessibility. |
int
|
getSelectionModeForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the selection mode for accessibility. |
int
|
getTopDecorationHeight(View child)
Returns the total height of item decorations applied to child's top. |
void
|
getTransformedBoundingBox(View child, boolean includeDecorInsets, Rect out)
Calculates the bounding box of the View while taking into account its matrix changes (translation, scale etc) with respect to the RecyclerView. |
int
|
getWidth()
Returns the width that is currently relevant to the LayoutManager. |
int
|
getWidthMode()
Return the width measurement spec mode that is currently relevant to the LayoutManager. |
boolean
|
hasFocus()
Returns true if the RecyclerView this LayoutManager is bound to has or contains focus. |
void
|
ignoreView(View view)
Flags a view so that it will not be scrapped or recycled. |
boolean
|
isAttachedToWindow()
Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window. |
boolean
|
isAutoMeasureEnabled()
Returns whether the measuring pass of layout should use the AutoMeasure mechanism of
|
boolean
|
isFocused()
Returns true if the RecyclerView this LayoutManager is bound to has focus. |
final
boolean
|
isItemPrefetchEnabled()
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames. |
boolean
|
isLayoutHierarchical(RecyclerView.Recycler recycler, RecyclerView.State state)
Returns whether layout is hierarchical or not to be used for accessibility. |
boolean
|
isMeasurementCacheEnabled()
In addition to the View Framework's measurement cache, RecyclerView uses its own additional measurement cache for its children to avoid re-measuring them when not necessary. |
boolean
|
isSmoothScrolling()
|
boolean
|
isViewPartiallyVisible(View child, boolean completelyVisible, boolean acceptEndPointInclusion)
Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters. |
void
|
layoutDecorated(View child, int left, int top, int right, int bottom)
Lay out the given child view within the RecyclerView using coordinates that
include any current |
void
|
layoutDecoratedWithMargins(View child, int left, int top, int right, int bottom)
Lay out the given child view within the RecyclerView using coordinates that
include any current |
void
|
measureChild(View child, int widthUsed, int heightUsed)
Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView and any added item decorations into account. |
void
|
measureChildWithMargins(View child, int widthUsed, int heightUsed)
Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView, any added item decorations and the child margins into account. |
void
|
moveView(int fromIndex, int toIndex)
Moves a View from one position to another. |
void
|
offsetChildrenHorizontal(int dx)
Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis. |
void
|
offsetChildrenVertical(int dy)
Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis. |
void
|
onAdapterChanged(Adapter oldAdapter, Adapter newAdapter)
Called if the RecyclerView this LayoutManager is bound to has a different adapter set via
|
boolean
|
onAddFocusables(RecyclerView recyclerView, ArrayList<View> views, int direction, int focusableMode)
Called to populate focusable views within the RecyclerView. |
void
|
onAttachedToWindow(RecyclerView view)
Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window. |
void
|
onDetachedFromWindow(RecyclerView view, RecyclerView.Recycler recycler)
Called when this LayoutManager is detached from its parent RecyclerView or when its parent RecyclerView is detached from its window. |
void
|
onDetachedFromWindow(RecyclerView view)
This method was deprecated
in API level 22.1.0.
override |
View
|
onFocusSearchFailed(View focused, int direction, RecyclerView.Recycler recycler, RecyclerView.State state)
Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView. |
void
|
onInitializeAccessibilityEvent(AccessibilityEvent event)
|
void
|
onInitializeAccessibilityEvent(RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityEvent event)
Called by the accessibility delegate to initialize an accessibility event. |
void
|
onInitializeAccessibilityNodeInfo(RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityNodeInfoCompat info)
Called by the AccessibilityDelegate when the information about the current layout should be populated. |
void
|
onInitializeAccessibilityNodeInfoForItem(RecyclerView.Recycler recycler, RecyclerView.State state, View host, AccessibilityNodeInfoCompat info)
Called by the AccessibilityDelegate when the accessibility information for a specific item should be populated. |
View
|
onInterceptFocusSearch(View focused, int direction)
This method gives a LayoutManager an opportunity to intercept the initial focus search
before the default behavior of |
void
|
onItemsAdded(RecyclerView recyclerView, int positionStart, int itemCount)
Called when items have been added to the adapter. |
void
|
onItemsChanged(RecyclerView recyclerView)
Called in response to a call to |
void
|
onItemsMoved(RecyclerView recyclerView, int from, int to, int itemCount)
Called when an item is moved withing the adapter. |
void
|
onItemsRemoved(RecyclerView recyclerView, int positionStart, int itemCount)
Called when items have been removed from the adapter. |
void
|
onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount)
Called when items have been changed in the adapter. |
void
|
onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount, Object payload)
Called when items have been changed in the adapter and with optional payload. |
void
|
onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)
Lay out all relevant child views from the given adapter. |
void
|
onLayoutCompleted(RecyclerView.State state)
Called after a full layout calculation is finished. |
void
|
onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec)
Measure the attached RecyclerView. |
boolean
|
onRequestChildFocus(RecyclerView parent, View child, View focused)
This method was deprecated
in API level 22.1.0.
Use |
boolean
|
onRequestChildFocus(RecyclerView parent, RecyclerView.State state, View child, View focused)
Called when a descendant view of the RecyclerView requests focus. |
void
|
onRestoreInstanceState(Parcelable state)
|
Parcelable
|
onSaveInstanceState()
Called when the LayoutManager should save its state. |
void
|
onScrollStateChanged(int state)
RecyclerView calls this method to notify LayoutManager that scroll state has changed. |
boolean
|
performAccessibilityAction(RecyclerView.Recycler recycler, RecyclerView.State state, int action, Bundle args)
Called by AccessibilityDelegate when an action is requested from the RecyclerView. |
boolean
|
performAccessibilityActionForItem(RecyclerView.Recycler recycler, RecyclerView.State state, View view, int action, Bundle args)
Called by AccessibilityDelegate when an accessibility action is requested on one of the children of LayoutManager. |
void
|
postOnAnimation(Runnable action)
Causes the Runnable to execute on the next animation time step. |
void
|
removeAllViews()
Remove all views from the currently attached RecyclerView. |
void
|
removeAndRecycleAllViews(RecyclerView.Recycler recycler)
Removes all views and recycles them using the given recycler. |
void
|
removeAndRecycleView(View child, RecyclerView.Recycler recycler)
Remove a child view and recycle it using the given Recycler. |
void
|
removeAndRecycleViewAt(int index, RecyclerView.Recycler recycler)
Remove a child view and recycle it using the given Recycler. |
boolean
|
removeCallbacks(Runnable action)
Removes the specified Runnable from the message queue. |
void
|
removeDetachedView(View child)
Finish removing a view that was previously temporarily
|
void
|
removeView(View child)
Remove a view from the currently attached RecyclerView if needed. |
void
|
removeViewAt(int index)
Remove a view from the currently attached RecyclerView if needed. |
boolean
|
requestChildRectangleOnScreen(RecyclerView parent, View child, Rect rect, boolean immediate, boolean focusedChildVisible)
Requests that the given child of the RecyclerView be positioned onto the screen. |
boolean
|
requestChildRectangleOnScreen(RecyclerView parent, View child, Rect rect, boolean immediate)
Called when a child of the RecyclerView wants a particular rectangle to be positioned onto the screen. |
void
|
requestLayout()
Calls |
void
|
requestSimpleAnimationsInNextLayout()
A LayoutManager can call this method to force RecyclerView to run simple animations in the next layout pass, even if there is not any trigger to do so. |
int
|
scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state)
Scroll horizontally by dx pixels in screen coordinates and return the distance traveled. |
void
|
scrollToPosition(int position)
Scroll to the specified adapter position. |
int
|
scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state)
Scroll vertically by dy pixels in screen coordinates and return the distance traveled. |
void
|
setAutoMeasureEnabled(boolean enabled)
This method was deprecated
in API level 27.1.0.
Implementors of LayoutManager should define whether or not it uses
AutoMeasure by overriding |
final
void
|
setItemPrefetchEnabled(boolean enabled)
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames. |
void
|
setMeasuredDimension(int widthSize, int heightSize)
|
void
|
setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec)
Sets the measured dimensions from the given bounding box of the children and the
measurement specs that were passed into |
void
|
setMeasurementCacheEnabled(boolean measurementCacheEnabled)
Sets whether RecyclerView should use its own measurement cache for the children. |
void
|
smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position)
Smooth scroll to the specified adapter position. |
void
|
startSmoothScroll(RecyclerView.SmoothScroller smoothScroller)
Starts a smooth scroll using the provided SmoothScroller. |
void
|
stopIgnoringView(View view)
View can be scrapped and recycled again. |
boolean
|
supportsPredictiveItemAnimations()
Returns whether this LayoutManager supports "predictive item animations". |
Inherited methods | |
---|---|
From
class
java.lang.Object
|
XML attributes
RecyclerView_android_orientation
Related methods:
RecyclerView_reverseLayout
Related methods:
RecyclerView_spanCount
Related methods:
RecyclerView_stackFromEnd
Related methods:
Public constructors
Public methods
addDisappearingView
void addDisappearingView (View child, int index)
To be called only during onLayoutChildren(Recycler, State)
to add a view
to the layout that is known to be going away, either because it has been
removed
or because it is actually not in the
visible portion of the container but is being laid out in order to inform RecyclerView
in how to animate the item out of view.
Views added via this method are going to be invisible to LayoutManager after the
dispatchLayout pass is complete. They cannot be retrieved via getChildAt(int)
or won't be included in getChildCount()
method.
Parameters | |
---|---|
child |
View : View to add and then remove with animation. |
index |
int : Index of the view.
|
addDisappearingView
void addDisappearingView (View child)
To be called only during onLayoutChildren(Recycler, State)
to add a view
to the layout that is known to be going away, either because it has been
removed
or because it is actually not in the
visible portion of the container but is being laid out in order to inform RecyclerView
in how to animate the item out of view.
Views added via this method are going to be invisible to LayoutManager after the
dispatchLayout pass is complete. They cannot be retrieved via getChildAt(int)
or won't be included in getChildCount()
method.
Parameters | |
---|---|
child |
View : View to add and then remove with animation.
|
addView
void addView (View child, int index)
Add a view to the currently attached RecyclerView if needed. LayoutManagers should
use this method to add views obtained from a RecyclerView.Recycler
using
getViewForPosition(int)
.
Parameters | |
---|---|
child |
View : View to add |
index |
int : Index to add child at
|
addView
void addView (View child)
Add a view to the currently attached RecyclerView if needed. LayoutManagers should
use this method to add views obtained from a RecyclerView.Recycler
using
getViewForPosition(int)
.
Parameters | |
---|---|
child |
View : View to add
|
assertInLayoutOrScroll
void assertInLayoutOrScroll (String message)
Checks if RecyclerView is in the middle of a layout or scroll and throws an
IllegalStateException
if it is not.
Parameters | |
---|---|
message |
String : The message for the exception. Can be null. |
See also:
assertNotInLayoutOrScroll
void assertNotInLayoutOrScroll (String message)
Checks if RecyclerView is in the middle of a layout or scroll and throws an
IllegalStateException
if it is.
Parameters | |
---|---|
message |
String : The message for the exception. Can be null. |
See also:
attachView
void attachView (View child)
Reattach a previously detached
view.
This method should not be used to reattach views that were previously
detachAndScrapView(android.view.View, RecyclerView.Recycler)
scrapped}.
Parameters | |
---|---|
child |
View : Child to reattach
|
attachView
void attachView (View child, int index)
Reattach a previously detached
view.
This method should not be used to reattach views that were previously
detachAndScrapView(android.view.View, RecyclerView.Recycler)
scrapped}.
Parameters | |
---|---|
child |
View : Child to reattach |
index |
int : Intended child index for child
|
attachView
void attachView (View child, int index, RecyclerView.LayoutParams lp)
Reattach a previously detached
view.
This method should not be used to reattach views that were previously
detachAndScrapView(android.view.View, RecyclerView.Recycler)
scrapped}.
Parameters | |
---|---|
child |
View : Child to reattach |
index |
int : Intended child index for child |
lp |
RecyclerView.LayoutParams : LayoutParams for child
|
calculateItemDecorationsForChild
void calculateItemDecorationsForChild (View child, Rect outRect)
Calculates the item decor insets applied to the given child and updates the provided Rect instance with the inset values.
- The Rect's left is set to the total width of left decorations.
- The Rect's top is set to the total height of top decorations.
- The Rect's right is set to the total width of right decorations.
- The Rect's bottom is set to total height of bottom decorations.
Note that item decorations are automatically calculated when one of the LayoutManager's
measure child methods is called. If you need to measure the child with custom specs via
measure(int, int)
, you can use this method to get decorations.
Parameters | |
---|---|
child |
View : The child view whose decorations should be calculated |
outRect |
Rect : The Rect to hold result values
|
canScrollHorizontally
boolean canScrollHorizontally ()
Query if horizontal scrolling is currently supported. The default implementation returns false.
Returns | |
---|---|
boolean |
True if this LayoutManager can scroll the current contents horizontally |
canScrollVertically
boolean canScrollVertically ()
Query if vertical scrolling is currently supported. The default implementation returns false.
Returns | |
---|---|
boolean |
True if this LayoutManager can scroll the current contents vertically |
checkLayoutParams
boolean checkLayoutParams (RecyclerView.LayoutParams lp)
Determines the validity of the supplied LayoutParams object.
This should check to make sure that the object is of the correct type
and all values are within acceptable ranges. The default implementation
returns true
for non-null params.
Parameters | |
---|---|
lp |
RecyclerView.LayoutParams : LayoutParams object to check |
Returns | |
---|---|
boolean |
true if this LayoutParams object is valid, false otherwise |
chooseSize
int chooseSize (int spec, int desired, int min)
Chooses a size from the given specs and parameters that is closest to the desired size and also complies with the spec.
Parameters | |
---|---|
spec |
int : The measureSpec |
desired |
int : The preferred measurement |
min |
int : The minimum value |
Returns | |
---|---|
int |
A size that fits to the given specs |
collectAdjacentPrefetchPositions
void collectAdjacentPrefetchPositions (int dx, int dy, RecyclerView.State state, RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)
Gather all positions from the LayoutManager to be prefetched, given specified momentum.
If item prefetch is enabled, this method is called in between traversals to gather which positions the LayoutManager will soon need, given upcoming movement in subsequent traversals.
The LayoutManager should call addPosition(int, int)
for
each item to be prepared, and these positions will have their ViewHolders created and
bound, if there is sufficient time available, in advance of being needed by a
scroll or layout.
Parameters | |
---|---|
dx |
int : X movement component. |
dy |
int : Y movement component. |
state |
RecyclerView.State : State of RecyclerView |
layoutPrefetchRegistry |
RecyclerView.LayoutManager.LayoutPrefetchRegistry : PrefetchRegistry to add prefetch entries into. |
collectInitialPrefetchPositions
void collectInitialPrefetchPositions (int adapterItemCount, RecyclerView.LayoutManager.LayoutPrefetchRegistry layoutPrefetchRegistry)
Gather all positions from the LayoutManager to be prefetched in preperation for its RecyclerView to come on screen, due to the movement of another, containing RecyclerView.
This method is only called when a RecyclerView is nested in another RecyclerView.
If item prefetch is enabled for this LayoutManager, as well in another containing LayoutManager, this method is called in between draw traversals to gather which positions this LayoutManager will first need, once it appears on the screen.
For example, if this LayoutManager represents a horizontally scrolling list within a vertically scrolling LayoutManager, this method would be called when the horizontal list is about to come onscreen.
The LayoutManager should call addPosition(int, int)
for
each item to be prepared, and these positions will have their ViewHolders created and
bound, if there is sufficient time available, in advance of being needed by a
scroll or layout.
Parameters | |
---|---|
adapterItemCount |
int : number of items in the associated adapter. |
layoutPrefetchRegistry |
RecyclerView.LayoutManager.LayoutPrefetchRegistry : PrefetchRegistry to add prefetch entries into. |
computeHorizontalScrollExtent
int computeHorizontalScrollExtent (RecyclerView.State state)
Override this method if you want to support scroll bars.
Read computeHorizontalScrollExtent()
for details.
Default implementation returns 0.
Parameters | |
---|---|
state |
RecyclerView.State : Current state of RecyclerView |
Returns | |
---|---|
int |
The horizontal extent of the scrollbar's thumb |
See also:
computeHorizontalScrollOffset
int computeHorizontalScrollOffset (RecyclerView.State state)
Override this method if you want to support scroll bars.
Read computeHorizontalScrollOffset()
for details.
Default implementation returns 0.
Parameters | |
---|---|
state |
RecyclerView.State : Current State of RecyclerView where you can find total item count |
Returns | |
---|---|
int |
The horizontal offset of the scrollbar's thumb |
See also:
computeHorizontalScrollRange
int computeHorizontalScrollRange (RecyclerView.State state)
Override this method if you want to support scroll bars.
Read computeHorizontalScrollRange()
for details.
Default implementation returns 0.
Parameters | |
---|---|
state |
RecyclerView.State : Current State of RecyclerView where you can find total item count |
Returns | |
---|---|
int |
The total horizontal range represented by the vertical scrollbar |
See also:
computeVerticalScrollExtent
int computeVerticalScrollExtent (RecyclerView.State state)
Override this method if you want to support scroll bars.
Read computeVerticalScrollExtent()
for details.
Default implementation returns 0.
Parameters | |
---|---|
state |
RecyclerView.State : Current state of RecyclerView |
Returns | |
---|---|
int |
The vertical extent of the scrollbar's thumb |
See also:
computeVerticalScrollOffset
int computeVerticalScrollOffset (RecyclerView.State state)
Override this method if you want to support scroll bars.
Read computeVerticalScrollOffset()
for details.
Default implementation returns 0.
Parameters | |
---|---|
state |
RecyclerView.State : Current State of RecyclerView where you can find total item count |
Returns | |
---|---|
int |
The vertical offset of the scrollbar's thumb |
See also:
computeVerticalScrollRange
int computeVerticalScrollRange (RecyclerView.State state)
Override this method if you want to support scroll bars.
Read computeVerticalScrollRange()
for details.
Default implementation returns 0.
Parameters | |
---|---|
state |
RecyclerView.State : Current State of RecyclerView where you can find total item count |
Returns | |
---|---|
int |
The total vertical range represented by the vertical scrollbar |
See also:
detachAndScrapAttachedViews
void detachAndScrapAttachedViews (RecyclerView.Recycler recycler)
Temporarily detach and scrap all currently attached child views. Views will be scrapped into the given Recycler. The Recycler may prefer to reuse scrap views before other views that were previously recycled.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : Recycler to scrap views into
|
detachAndScrapView
void detachAndScrapView (View child, RecyclerView.Recycler recycler)
Detach a child view and add it to a Recycler's
scrap heap.
Scrapping a view allows it to be rebound and reused to show updated or different data.
Parameters | |
---|---|
child |
View : Child to detach and scrap |
recycler |
RecyclerView.Recycler : Recycler to deposit the new scrap view into
|
detachAndScrapViewAt
void detachAndScrapViewAt (int index, RecyclerView.Recycler recycler)
Detach a child view and add it to a Recycler's
scrap heap.
Scrapping a view allows it to be rebound and reused to show updated or different data.
Parameters | |
---|---|
index |
int : Index of child to detach and scrap |
recycler |
RecyclerView.Recycler : Recycler to deposit the new scrap view into
|
detachView
void detachView (View child)
Temporarily detach a child view.
LayoutManagers may want to perform a lightweight detach operation to rearrange
views currently attached to the RecyclerView. Generally LayoutManager implementations
will want to use detachAndScrapView(android.view.View, RecyclerView.Recycler)
so that the detached view may be rebound and reused.
If a LayoutManager uses this method to detach a view, it must
reattach
or fully remove
the detached view
before the LayoutManager entry point method called by RecyclerView returns.
Parameters | |
---|---|
child |
View : Child to detach
|
detachViewAt
void detachViewAt (int index)
Temporarily detach a child view.
LayoutManagers may want to perform a lightweight detach operation to rearrange
views currently attached to the RecyclerView. Generally LayoutManager implementations
will want to use detachAndScrapView(android.view.View, RecyclerView.Recycler)
so that the detached view may be rebound and reused.
If a LayoutManager uses this method to detach a view, it must
reattach
or fully remove
the detached view
before the LayoutManager entry point method called by RecyclerView returns.
Parameters | |
---|---|
index |
int : Index of the child to detach
|
endAnimation
void endAnimation (View view)
Ends all animations on the view created by the RecyclerView.ItemAnimator
.
Parameters | |
---|---|
view |
View : The View for which the animations should be ended. |
See also:
findContainingItemView
View findContainingItemView (View view)
Traverses the ancestors of the given view and returns the item view that contains it and also a direct child of the LayoutManager.
Note that this method may return null if the view is a child of the RecyclerView but not a child of the LayoutManager (e.g. running a disappear animation).
Parameters | |
---|---|
view |
View : The view that is a descendant of the LayoutManager. |
Returns | |
---|---|
View |
The direct child of the LayoutManager which contains the given view or null if the provided view is not a descendant of this LayoutManager. |
findViewByPosition
View findViewByPosition (int position)
Finds the view which represents the given adapter position.
This method traverses each child since it has no information about child order. Override this method to improve performance if your LayoutManager keeps data about child views.
If a view is ignored via ignoreView(View)
, it is also ignored by this method.
Parameters | |
---|---|
position |
int : Position of the item in adapter |
Returns | |
---|---|
View |
The child view that represents the given position or null if the position is not laid out |
generateDefaultLayoutParams
RecyclerView.LayoutParams generateDefaultLayoutParams ()
Create a default LayoutParams
object for a child of the RecyclerView.
LayoutManagers will often want to use a custom LayoutParams
type
to store extra information specific to the layout. Client code should subclass
RecyclerView.LayoutParams
for this purpose.
Important: if you use your own custom LayoutParams
type
you must also override
checkLayoutParams(LayoutParams)
,
generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
Returns | |
---|---|
RecyclerView.LayoutParams |
A new LayoutParams for a child view |
generateLayoutParams
RecyclerView.LayoutParams generateLayoutParams (Context c, AttributeSet attrs)
Create a LayoutParams object suitable for this LayoutManager from an inflated layout resource.
Important: if you use your own custom LayoutParams
type
you must also override
checkLayoutParams(LayoutParams)
,
generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
Parameters | |
---|---|
c |
Context : Context for obtaining styled attributes |
attrs |
AttributeSet : AttributeSet describing the supplied arguments |
Returns | |
---|---|
RecyclerView.LayoutParams |
a new LayoutParams object |
generateLayoutParams
RecyclerView.LayoutParams generateLayoutParams (ViewGroup.LayoutParams lp)
Create a LayoutParams object suitable for this LayoutManager, copying relevant values from the supplied LayoutParams object if possible.
Important: if you use your own custom LayoutParams
type
you must also override
checkLayoutParams(LayoutParams)
,
generateLayoutParams(android.view.ViewGroup.LayoutParams)
and
generateLayoutParams(android.content.Context, android.util.AttributeSet)
.
Parameters | |
---|---|
lp |
ViewGroup.LayoutParams : Source LayoutParams object to copy values from |
Returns | |
---|---|
RecyclerView.LayoutParams |
a new LayoutParams object |
getBaseline
int getBaseline ()
Returns offset of the RecyclerView's text baseline from the its top boundary.
Returns | |
---|---|
int |
The offset of the RecyclerView's text baseline from the its top boundary; -1 if there is no baseline. |
getBottomDecorationHeight
int getBottomDecorationHeight (View child)
Returns the total height of item decorations applied to child's bottom.
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
The total height of item decorations applied to the child's bottom. |
getChildAt
View getChildAt (int index)
Return the child view at the given index
Parameters | |
---|---|
index |
int : Index of child to return |
Returns | |
---|---|
View |
Child view at index |
getChildCount
int getChildCount ()
Return the current number of child views attached to the parent RecyclerView. This does not include child views that were temporarily detached and/or scrapped.
Returns | |
---|---|
int |
Number of attached children |
getChildMeasureSpec
int getChildMeasureSpec (int parentSize, int parentMode, int padding, int childDimension, boolean canScroll)
Calculate a MeasureSpec value for measuring a child view in one dimension.
Parameters | |
---|---|
parentSize |
int : Size of the parent view where the child will be placed |
parentMode |
int : The measurement spec mode of the parent |
padding |
int : Total space currently consumed by other elements of parent |
childDimension |
int : Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT.
Generally obtained from the child view's LayoutParams |
canScroll |
boolean : true if the parent RecyclerView can scroll in this dimension |
Returns | |
---|---|
int |
a MeasureSpec value for the child view |
getChildMeasureSpec
int getChildMeasureSpec (int parentSize, int padding, int childDimension, boolean canScroll)
This method was deprecated
in API level 24.1.0.
use getChildMeasureSpec(int, int, int, int, boolean)
Calculate a MeasureSpec value for measuring a child view in one dimension.
Parameters | |
---|---|
parentSize |
int : Size of the parent view where the child will be placed |
padding |
int : Total space currently consumed by other elements of the parent |
childDimension |
int : Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT.
Generally obtained from the child view's LayoutParams |
canScroll |
boolean : true if the parent RecyclerView can scroll in this dimension |
Returns | |
---|---|
int |
a MeasureSpec value for the child view |
getClipToPadding
boolean getClipToPadding ()
Check if the RecyclerView is configured to clip child views to its padding.
Returns | |
---|---|
boolean |
true if this RecyclerView clips children to its padding, false otherwise |
getColumnCountForAccessibility
int getColumnCountForAccessibility (RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the number of columns for accessibility.
Default implementation returns the number of items in the adapter if LayoutManager supports horizontal scrolling or 1 if LayoutManager does not support horizontal scrolling.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
Returns | |
---|---|
int |
The number of rows in LayoutManager for accessibility. |
getDecoratedBottom
int getDecoratedBottom (View child)
Returns the bottom edge of the given child view within its parent, offset by any applied
ItemDecorations
.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
Child bottom edge with offsets applied |
See also:
getDecoratedBoundsWithMargins
void getDecoratedBoundsWithMargins (View view, Rect outBounds)
Returns the bounds of the view including its decoration and margins.
Parameters | |
---|---|
view |
View : The view element to check |
outBounds |
Rect : A rect that will receive the bounds of the element including its
decoration and margins.
|
getDecoratedLeft
int getDecoratedLeft (View child)
Returns the left edge of the given child view within its parent, offset by any applied
ItemDecorations
.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
Child left edge with offsets applied |
See also:
getDecoratedMeasuredHeight
int getDecoratedMeasuredHeight (View child)
Returns the measured height of the given child, plus the additional size of
any insets applied by ItemDecorations
.
Parameters | |
---|---|
child |
View : Child view to query |
Returns | |
---|---|
int |
child's measured height plus ItemDecoration insets |
See also:
getDecoratedMeasuredWidth
int getDecoratedMeasuredWidth (View child)
Returns the measured width of the given child, plus the additional size of
any insets applied by ItemDecorations
.
Parameters | |
---|---|
child |
View : Child view to query |
Returns | |
---|---|
int |
child's measured width plus ItemDecoration insets |
See also:
getDecoratedRight
int getDecoratedRight (View child)
Returns the right edge of the given child view within its parent, offset by any applied
ItemDecorations
.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
Child right edge with offsets applied |
See also:
getDecoratedTop
int getDecoratedTop (View child)
Returns the top edge of the given child view within its parent, offset by any applied
ItemDecorations
.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
Child top edge with offsets applied |
See also:
getFocusedChild
View getFocusedChild ()
Returns the item View which has or contains focus.
Returns | |
---|---|
View |
A direct child of RecyclerView which has focus or contains the focused child. |
getHeight
int getHeight ()
Returns the height that is currently relevant to the LayoutManager.
This value is usually equal to the laid out height of the RecyclerView
but may
reflect the current View.MeasureSpec
height if the
RecyclerView.LayoutManager
is using AutoMeasure and the RecyclerView is in the process of
measuring. The LayoutManager must always use this method to retrieve the height relevant
to it at any given time.
Returns | |
---|---|
int |
Height in pixels |
getHeightMode
int getHeightMode ()
Return the height measurement spec mode that is currently relevant to the LayoutManager.
This value is set only if the LayoutManager opts into the AutoMeasure api via
setAutoMeasureEnabled(boolean)
.
When RecyclerView is running a layout, this value is always set to
EXACTLY
even if it was measured with a different spec mode.
Returns | |
---|---|
int |
Height measure spec mode |
See also:
getItemCount
int getItemCount ()
Returns the number of items in the adapter bound to the parent RecyclerView.
Note that this number is not necessarily equal to
State#getItemCount()
. In methods where RecyclerView.State
is
available, you should use State#getItemCount()
instead.
For more details, check the documentation for
State#getItemCount()
.
Returns | |
---|---|
int |
The number of items in the bound adapter |
See also:
getItemViewType
int getItemViewType (View view)
Returns the View type defined by the adapter.
Parameters | |
---|---|
view |
View : The view to query |
Returns | |
---|---|
int |
The type of the view assigned by the adapter. |
getLayoutDirection
int getLayoutDirection ()
Returns the resolved layout direction for this RecyclerView.
Returns | |
---|---|
int |
LAYOUT_DIRECTION_RTL if the layout
direction is RTL or returns
LAYOUT_DIRECTION_LTR if the layout direction
is not RTL.
|
getLeftDecorationWidth
int getLeftDecorationWidth (View child)
Returns the total width of item decorations applied to child's left.
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
The total width of item decorations applied to the child's left. |
getMinimumHeight
int getMinimumHeight ()
Returns | |
---|---|
int |
The host RecyclerView's getMinimumHeight()
|
getMinimumWidth
int getMinimumWidth ()
Returns | |
---|---|
int |
The host RecyclerView's getMinimumWidth()
|
getPaddingBottom
int getPaddingBottom ()
Return the bottom padding of the parent RecyclerView
Returns | |
---|---|
int |
Padding in pixels |
getPaddingEnd
int getPaddingEnd ()
Return the end padding of the parent RecyclerView
Returns | |
---|---|
int |
Padding in pixels |
getPaddingLeft
int getPaddingLeft ()
Return the left padding of the parent RecyclerView
Returns | |
---|---|
int |
Padding in pixels |
getPaddingRight
int getPaddingRight ()
Return the right padding of the parent RecyclerView
Returns | |
---|---|
int |
Padding in pixels |
getPaddingStart
int getPaddingStart ()
Return the start padding of the parent RecyclerView
Returns | |
---|---|
int |
Padding in pixels |
getPaddingTop
int getPaddingTop ()
Return the top padding of the parent RecyclerView
Returns | |
---|---|
int |
Padding in pixels |
getPosition
int getPosition (View view)
Returns the adapter position of the item represented by the given View. This does not contain any adapter changes that might have happened after the last layout.
Parameters | |
---|---|
view |
View : The view to query |
Returns | |
---|---|
int |
The adapter position of the item which is rendered by this View. |
getProperties
RecyclerView.LayoutManager.Properties getProperties (Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
Parse the xml attributes to get the most common properties used by layout managers.
Related XML Attributes:
- RecyclerView_android_orientation
- RecyclerView_spanCount
- RecyclerView_reverseLayout
- RecyclerView_stackFromEnd
Parameters | |
---|---|
context |
Context |
attrs |
AttributeSet |
defStyleAttr |
int |
defStyleRes |
int |
Returns | |
---|---|
RecyclerView.LayoutManager.Properties |
an object containing the properties as specified in the attrs. |
getRightDecorationWidth
int getRightDecorationWidth (View child)
Returns the total width of item decorations applied to child's right.
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
The total width of item decorations applied to the child's right. |
getRowCountForAccessibility
int getRowCountForAccessibility (RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the number of rows for accessibility.
Default implementation returns the number of items in the adapter if LayoutManager supports vertical scrolling or 1 if LayoutManager does not support vertical scrolling.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
Returns | |
---|---|
int |
The number of rows in LayoutManager for accessibility. |
getSelectionModeForAccessibility
int getSelectionModeForAccessibility (RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the selection mode for accessibility. Should be
SELECTION_MODE_NONE
,
SELECTION_MODE_SINGLE
or
SELECTION_MODE_MULTIPLE
.
Default implementation returns
SELECTION_MODE_NONE
.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
Returns | |
---|---|
int |
Selection mode for accessibility. Default implementation returns
SELECTION_MODE_NONE .
|
getTopDecorationHeight
int getTopDecorationHeight (View child)
Returns the total height of item decorations applied to child's top.
Note that this value is not updated until the View is measured or
calculateItemDecorationsForChild(View, Rect)
is called.
Parameters | |
---|---|
child |
View : Child to query |
Returns | |
---|---|
int |
The total height of item decorations applied to the child's top. |
getTransformedBoundingBox
void getTransformedBoundingBox (View child, boolean includeDecorInsets, Rect out)
Calculates the bounding box of the View while taking into account its matrix changes (translation, scale etc) with respect to the RecyclerView.
If includeDecorInsets
is true
, they are applied first before applying
the View's matrix so that the decor offsets also go through the same transformation.
Parameters | |
---|---|
child |
View : The ItemView whose bounding box should be calculated. |
includeDecorInsets |
boolean : True if the decor insets should be included in the bounding box |
out |
Rect : The rectangle into which the output will be written.
|
getWidth
int getWidth ()
Returns the width that is currently relevant to the LayoutManager.
This value is usually equal to the laid out width of the RecyclerView
but may
reflect the current View.MeasureSpec
width if the
RecyclerView.LayoutManager
is using AutoMeasure and the RecyclerView is in the process of
measuring. The LayoutManager must always use this method to retrieve the width relevant
to it at any given time.
Returns | |
---|---|
int |
Width in pixels |
getWidthMode
int getWidthMode ()
Return the width measurement spec mode that is currently relevant to the LayoutManager.
This value is set only if the LayoutManager opts into the AutoMeasure api via
setAutoMeasureEnabled(boolean)
.
When RecyclerView is running a layout, this value is always set to
EXACTLY
even if it was measured with a different spec mode.
Returns | |
---|---|
int |
Width measure spec mode |
See also:
hasFocus
boolean hasFocus ()
Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.
Returns | |
---|---|
boolean |
true if the RecyclerView has or contains focus |
See also:
ignoreView
void ignoreView (View view)
Flags a view so that it will not be scrapped or recycled.
Scope of ignoring a child is strictly restricted to position tracking, scrapping and
recyling. Methods like removeAndRecycleAllViews(Recycler)
will ignore the child
whereas removeAllViews()
or offsetChildrenHorizontal(int)
will not
ignore the child.
Before this child can be recycled again, you have to call
stopIgnoringView(View)
.
You can call this method only if your LayoutManger is in onLayout or onScroll callback.
Parameters | |
---|---|
view |
View : View to ignore. |
See also:
isAttachedToWindow
boolean isAttachedToWindow ()
Returns whether LayoutManager is currently attached to a RecyclerView which is attached to a window.
Returns | |
---|---|
boolean |
True if this LayoutManager is controlling a RecyclerView and the RecyclerView is attached to window. |
isAutoMeasureEnabled
boolean isAutoMeasureEnabled ()
Returns whether the measuring pass of layout should use the AutoMeasure mechanism of
RecyclerView
or if it should be done by the LayoutManager's implementation of
onMeasure(Recycler, State, int, int)
.
This method returns false by default (it actually returns the value passed to the
deprecated setAutoMeasureEnabled(boolean)
) and should be overridden to return
true if a LayoutManager wants to be auto measured by the RecyclerView.
If this method is overridden to return true,
onMeasure(Recycler, State, int, int)
should not be overridden.
AutoMeasure is a RecyclerView mechanism that handles the measuring pass of layout in a
simple and contract satisfying way, including the wrapping of children laid out by
LayoutManager. Simply put, it handles wrapping children by calling
onLayoutChildren(Recycler, State)
during a call to
onMeasure(int, int)
, and then calculating desired dimensions based
on children's dimensions and positions. It does this while supporting all existing
animation capabilities of the RecyclerView.
More specifically:
- When
onMeasure(int, int)
is called, if the provided measure specs both have a mode ofEXACTLY
, RecyclerView will set its measured dimensions accordingly and return, allowing layout to continue as normal (Actually, RecyclerView will callonMeasure(Recycler, State, int, int)
for backwards compatibility reasons but it should not be overridden if AutoMeasure is being used). - If one of the layout specs is not
EXACT
, the RecyclerView will start the layout process. It will first process all pending Adapter updates and then decide whether to run a predictive layout. If it decides to do so, it will first callonLayoutChildren(Recycler, State)
withisPreLayout()
set totrue
. At this stage,getWidth()
andgetHeight()
will still return the width and height of the RecyclerView as of the last layout calculation.After handling the predictive case, RecyclerView will call
onLayoutChildren(Recycler, State)
withisMeasuring()
set totrue
andisPreLayout()
set tofalse
. The LayoutManager can access the measurement specs viagetHeight()
,getHeightMode()
,getWidth()
andgetWidthMode()
. - After the layout calculation, RecyclerView sets the measured width & height by
calculating the bounding box for the children (+ RecyclerView's padding). The
LayoutManagers can override
setMeasuredDimension(Rect, int, int)
to choose different values. For instance, GridLayoutManager overrides this value to handle the case where if it is vertical and has 3 columns but only 2 items, it should still measure its width to fit 3 items, not 2. - Any following calls to
onMeasure(int, int)
will runonLayoutChildren(Recycler, State)
withisMeasuring()
set totrue
andisPreLayout()
set tofalse
. RecyclerView will take care of which views are actually added / removed / moved / changed for animations so that the LayoutManager should not worry about them and handle eachonLayoutChildren(Recycler, State)
call as if it is the last one. - When measure is complete and RecyclerView's
onLayout(boolean, int, int, int, int)
method is called, RecyclerView checks whether it already did layout calculations during the measure pass and if so, it re-uses that information. It may still decide to callonLayoutChildren(Recycler, State)
if the last measure spec was different from the final dimensions or adapter contents have changed between the measure call and the layout call. - Finally, animations are calculated and run as usual.
Returns | |
---|---|
boolean |
True if the measuring pass of layout should use the AutoMeasure
mechanism of RecyclerView or False if it should be done by the
LayoutManager's implementation of
onMeasure(Recycler, State, int, int) . |
isFocused
boolean isFocused ()
Returns true if the RecyclerView this LayoutManager is bound to has focus.
Returns | |
---|---|
boolean |
True if the RecyclerView has focus, false otherwise. |
See also:
isItemPrefetchEnabled
boolean isItemPrefetchEnabled ()
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.
Returns | |
---|---|
boolean |
true if item prefetch is enabled, false otherwise |
See also:
isLayoutHierarchical
boolean isLayoutHierarchical (RecyclerView.Recycler recycler, RecyclerView.State state)
Returns whether layout is hierarchical or not to be used for accessibility.
Default implementation returns false.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
Returns | |
---|---|
boolean |
True if layout is hierarchical. |
isMeasurementCacheEnabled
boolean isMeasurementCacheEnabled ()
In addition to the View Framework's measurement cache, RecyclerView uses its own
additional measurement cache for its children to avoid re-measuring them when not
necessary. It is on by default but it can be turned off via
setMeasurementCacheEnabled(boolean)
.
Returns | |
---|---|
boolean |
True if measurement cache is enabled, false otherwise. |
See also:
isSmoothScrolling
boolean isSmoothScrolling ()
Returns | |
---|---|
boolean |
true if RecyclerView is currently in the state of smooth scrolling. |
isViewPartiallyVisible
boolean isViewPartiallyVisible (View child, boolean completelyVisible, boolean acceptEndPointInclusion)
Returns whether the given child view is partially or fully visible within the padded bounded area of RecyclerView, depending on the input parameters. A view is partially visible if it has non-zero overlap with RV's padded bounded area. If acceptEndPointInclusion flag is set to true, it's also considered partially visible if it's located outside RV's bounds and it's hitting either RV's start or end bounds.
Parameters | |
---|---|
child |
View : The child view to be examined. |
completelyVisible |
boolean : If true, the method returns true if and only if the child is
completely visible. If false, the method returns true if and
only if the child is only partially visible (that is it will
return false if the child is either completely visible or out
of RV's bounds). |
acceptEndPointInclusion |
boolean : If the view's endpoint intersection with RV's start of end
bounds is enough to consider it partially visible,
false otherwise. |
Returns | |
---|---|
boolean |
True if the given child is partially or fully visible, false otherwise. |
layoutDecorated
void layoutDecorated (View child, int left, int top, int right, int bottom)
Lay out the given child view within the RecyclerView using coordinates that
include any current ItemDecorations
.
LayoutManagers should prefer working in sizes and coordinates that include item decoration insets whenever possible. This allows the LayoutManager to effectively ignore decoration insets within measurement and layout code. See the following methods:
layoutDecoratedWithMargins(View, int, int, int, int)
getDecoratedBoundsWithMargins(View, Rect)
measureChild(View, int, int)
measureChildWithMargins(View, int, int)
getDecoratedLeft(View)
getDecoratedTop(View)
getDecoratedRight(View)
getDecoratedBottom(View)
getDecoratedMeasuredWidth(View)
getDecoratedMeasuredHeight(View)
Parameters | |
---|---|
child |
View : Child to lay out |
left |
int : Left edge, with item decoration insets included |
top |
int : Top edge, with item decoration insets included |
right |
int : Right edge, with item decoration insets included |
bottom |
int : Bottom edge, with item decoration insets included |
layoutDecoratedWithMargins
void layoutDecoratedWithMargins (View child, int left, int top, int right, int bottom)
Lay out the given child view within the RecyclerView using coordinates that
include any current ItemDecorations
and margins.
LayoutManagers should prefer working in sizes and coordinates that include item decoration insets whenever possible. This allows the LayoutManager to effectively ignore decoration insets within measurement and layout code. See the following methods:
layoutDecorated(View, int, int, int, int)
measureChild(View, int, int)
measureChildWithMargins(View, int, int)
getDecoratedLeft(View)
getDecoratedTop(View)
getDecoratedRight(View)
getDecoratedBottom(View)
getDecoratedMeasuredWidth(View)
getDecoratedMeasuredHeight(View)
Parameters | |
---|---|
child |
View : Child to lay out |
left |
int : Left edge, with item decoration insets and left margin included |
top |
int : Top edge, with item decoration insets and top margin included |
right |
int : Right edge, with item decoration insets and right margin included |
bottom |
int : Bottom edge, with item decoration insets and bottom margin included |
measureChild
void measureChild (View child, int widthUsed, int heightUsed)
Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView and any added item decorations into account.
If the RecyclerView can be scrolled in either dimension the caller may pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.
Parameters | |
---|---|
child |
View : Child view to measure |
widthUsed |
int : Width in pixels currently consumed by other views, if relevant |
heightUsed |
int : Height in pixels currently consumed by other views, if relevant
|
measureChildWithMargins
void measureChildWithMargins (View child, int widthUsed, int heightUsed)
Measure a child view using standard measurement policy, taking the padding of the parent RecyclerView, any added item decorations and the child margins into account.
If the RecyclerView can be scrolled in either dimension the caller may pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.
Parameters | |
---|---|
child |
View : Child view to measure |
widthUsed |
int : Width in pixels currently consumed by other views, if relevant |
heightUsed |
int : Height in pixels currently consumed by other views, if relevant
|
moveView
void moveView (int fromIndex, int toIndex)
Moves a View from one position to another.
Parameters | |
---|---|
fromIndex |
int : The View's initial index |
toIndex |
int : The View's target index
|
offsetChildrenHorizontal
void offsetChildrenHorizontal (int dx)
Offset all child views attached to the parent RecyclerView by dx pixels along the horizontal axis.
Parameters | |
---|---|
dx |
int : Pixels to offset by
|
offsetChildrenVertical
void offsetChildrenVertical (int dy)
Offset all child views attached to the parent RecyclerView by dy pixels along the vertical axis.
Parameters | |
---|---|
dy |
int : Pixels to offset by
|
onAdapterChanged
void onAdapterChanged (Adapter oldAdapter, Adapter newAdapter)
Called if the RecyclerView this LayoutManager is bound to has a different adapter set via
setAdapter(Adapter)
or
swapAdapter(Adapter, boolean)
. The LayoutManager may use this
opportunity to clear caches and configure state such that it can relayout appropriately
with the new data and potentially new view types.
The default implementation removes all currently attached views.
Parameters | |
---|---|
oldAdapter |
Adapter : The previous adapter instance. Will be null if there was previously no
adapter. |
newAdapter |
Adapter : The new adapter instance. Might be null if
setAdapter(RecyclerView.Adapter) is called with null .
|
onAddFocusables
boolean onAddFocusables (RecyclerView recyclerView, ArrayList<View> views, int direction, int focusableMode)
Called to populate focusable views within the RecyclerView.
The LayoutManager implementation should return true
if the default
behavior of addFocusables(java.util.ArrayList, int)
should be
suppressed.
The default implementation returns false
to trigger RecyclerView
to fall back to the default ViewGroup behavior.
Parameters | |
---|---|
recyclerView |
RecyclerView : The RecyclerView hosting this LayoutManager |
views |
ArrayList : List of output views. This method should add valid focusable views
to this list. |
direction |
int : One of FOCUS_UP , FOCUS_DOWN ,
FOCUS_LEFT , FOCUS_RIGHT ,
FOCUS_BACKWARD , FOCUS_FORWARD |
focusableMode |
int : The type of focusables to be added. |
Returns | |
---|---|
boolean |
true to suppress the default behavior, false to add default focusables after this method returns. |
See also:
onAttachedToWindow
void onAttachedToWindow (RecyclerView view)
Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView is attached to a window.
If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not
call onLayoutChildren(Recycler, State)
if nothing has changed and a layout was
not requested on the RecyclerView while it was detached.
Subclass implementations should always call through to the superclass implementation.
Parameters | |
---|---|
view |
RecyclerView : The RecyclerView this LayoutManager is bound to |
onDetachedFromWindow
void onDetachedFromWindow (RecyclerView view, RecyclerView.Recycler recycler)
Called when this LayoutManager is detached from its parent RecyclerView or when its parent RecyclerView is detached from its window.
LayoutManager should clear all of its View references as another LayoutManager might be assigned to the RecyclerView.
If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not
call onLayoutChildren(Recycler, State)
if nothing has changed and a layout was
not requested on the RecyclerView while it was detached.
If your LayoutManager has View references that it cleans in on-detach, it should also
call requestLayout()
to ensure that it is re-laid out when
RecyclerView is re-attached.
Subclass implementations should always call through to the superclass implementation.
Parameters | |
---|---|
view |
RecyclerView : The RecyclerView this LayoutManager is bound to |
recycler |
RecyclerView.Recycler : The recycler to use if you prefer to recycle your children instead of
keeping them around. |
See also:
onDetachedFromWindow
void onDetachedFromWindow (RecyclerView view)
This method was deprecated
in API level 22.1.0.
override onDetachedFromWindow(RecyclerView, Recycler)
Parameters | |
---|---|
view |
RecyclerView |
onFocusSearchFailed
View onFocusSearchFailed (View focused, int direction, RecyclerView.Recycler recycler, RecyclerView.State state)
Called when searching for a focusable view in the given direction has failed for the current content of the RecyclerView.
This is the LayoutManager's opportunity to populate views in the given direction to fulfill the request if it can. The LayoutManager should attach and return the view to be focused, if a focusable view in the given direction is found. Otherwise, if all the existing (or the newly populated views) are unfocusable, it returns the next unfocusable view to become visible on the screen. This unfocusable view is typically the first view that's either partially or fully out of RV's padded bounded area in the given direction. The default implementation returns null.
Parameters | |
---|---|
focused |
View : The currently focused view |
direction |
int : One of FOCUS_UP , FOCUS_DOWN ,
FOCUS_LEFT , FOCUS_RIGHT ,
FOCUS_BACKWARD , FOCUS_FORWARD
or 0 for not applicable |
recycler |
RecyclerView.Recycler : The recycler to use for obtaining views for currently offscreen items |
state |
RecyclerView.State : Transient state of RecyclerView |
Returns | |
---|---|
View |
The chosen view to be focused if a focusable view is found, otherwise an unfocusable view to become visible onto the screen, else null. |
onInitializeAccessibilityEvent
void onInitializeAccessibilityEvent (AccessibilityEvent event)
Parameters | |
---|---|
event |
AccessibilityEvent |
onInitializeAccessibilityEvent
void onInitializeAccessibilityEvent (RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityEvent event)
Called by the accessibility delegate to initialize an accessibility event.
Default implementation adds item count and scroll information to the event.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
event |
AccessibilityEvent : The event instance to initialize |
onInitializeAccessibilityNodeInfo
void onInitializeAccessibilityNodeInfo (RecyclerView.Recycler recycler, RecyclerView.State state, AccessibilityNodeInfoCompat info)
Called by the AccessibilityDelegate when the information about the current layout should be populated.
Default implementation adds a AccessibilityNodeInfoCompat.CollectionInfoCompat
.
You should override
getRowCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
,
getColumnCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
,
isLayoutHierarchical(RecyclerView.Recycler, RecyclerView.State)
and
getSelectionModeForAccessibility(RecyclerView.Recycler, RecyclerView.State)
for
more accurate accessibility information.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
info |
AccessibilityNodeInfoCompat : The info that should be filled by the LayoutManager |
See also:
onInitializeAccessibilityNodeInfo(android.view.accessibility.AccessibilityNodeInfo)
getRowCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
getColumnCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
isLayoutHierarchical(RecyclerView.Recycler, RecyclerView.State)
getSelectionModeForAccessibility(RecyclerView.Recycler, RecyclerView.State)
onInitializeAccessibilityNodeInfoForItem
void onInitializeAccessibilityNodeInfoForItem (RecyclerView.Recycler recycler, RecyclerView.State state, View host, AccessibilityNodeInfoCompat info)
Called by the AccessibilityDelegate when the accessibility information for a specific item should be populated.
Default implementation adds basic positioning information about the item.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
host |
View : The child for which accessibility node info should be populated |
info |
AccessibilityNodeInfoCompat : The info to fill out about the item |
onInterceptFocusSearch
View onInterceptFocusSearch (View focused, int direction)
This method gives a LayoutManager an opportunity to intercept the initial focus search
before the default behavior of FocusFinder
is used. If this method returns
null FocusFinder will attempt to find a focusable child view. If it fails
then onFocusSearchFailed(View, int, RecyclerView.Recycler, RecyclerView.State)
will be called to give the LayoutManager an opportunity to add new views for items
that did not have attached views representing them. The LayoutManager should not add
or remove views from this method.
Parameters | |
---|---|
focused |
View : The currently focused view |
direction |
int : One of FOCUS_UP , FOCUS_DOWN ,
FOCUS_LEFT , FOCUS_RIGHT ,
FOCUS_BACKWARD , FOCUS_FORWARD |
Returns | |
---|---|
View |
A descendant view to focus or null to fall back to default behavior. The default implementation returns null. |
onItemsAdded
void onItemsAdded (RecyclerView recyclerView, int positionStart, int itemCount)
Called when items have been added to the adapter. The LayoutManager may choose to requestLayout if the inserted items would require refreshing the currently visible set of child views. (e.g. currently empty space would be filled by appended items, etc.)
onItemsChanged
void onItemsChanged (RecyclerView recyclerView)
Called in response to a call to notifyDataSetChanged()
or
swapAdapter(Adapter, boolean)
()} and signals that the the entire
data set has changed.
onItemsMoved
void onItemsMoved (RecyclerView recyclerView, int from, int to, int itemCount)
Called when an item is moved withing the adapter.
Note that, an item may also change position in response to another ADD/REMOVE/MOVE
operation. This callback is only called if and only if notifyItemMoved(int, int)
is called.
onItemsRemoved
void onItemsRemoved (RecyclerView recyclerView, int positionStart, int itemCount)
Called when items have been removed from the adapter.
onItemsUpdated
void onItemsUpdated (RecyclerView recyclerView, int positionStart, int itemCount)
Called when items have been changed in the adapter.
To receive payload, override onItemsUpdated(RecyclerView, int, int, Object)
instead, then this callback will not be invoked.
onItemsUpdated
void onItemsUpdated (RecyclerView recyclerView, int positionStart, int itemCount, Object payload)
Called when items have been changed in the adapter and with optional payload.
Default implementation calls onItemsUpdated(RecyclerView, int, int)
.
onLayoutChildren
void onLayoutChildren (RecyclerView.Recycler recycler, RecyclerView.State state)
Lay out all relevant child views from the given adapter.
The LayoutManager is in charge of the behavior of item animations. By default,
RecyclerView has a non-null ItemAnimator
, and simple
item animations are enabled. This means that add/remove operations on the
adapter will result in animations to add new or appearing items, removed or
disappearing items, and moved items. If a LayoutManager returns false from
supportsPredictiveItemAnimations()
, which is the default, and runs a
normal layout operation during onLayoutChildren(Recycler, State)
, the
RecyclerView will have enough information to run those animations in a simple
way. For example, the default ItemAnimator, DefaultItemAnimator
, will
simply fade views in and out, whether they are actually added/removed or whether
they are moved on or off the screen due to other add/remove operations.
A LayoutManager wanting a better item animation experience, where items can be
animated onto and off of the screen according to where the items exist when they
are not on screen, then the LayoutManager should return true from
supportsPredictiveItemAnimations()
and add additional logic to
onLayoutChildren(Recycler, State)
. Supporting predictive animations
means that onLayoutChildren(Recycler, State)
will be called twice;
once as a "pre" layout step to determine where items would have been prior to
a real layout, and again to do the "real" layout. In the pre-layout phase,
items will remember their pre-layout positions to allow them to be laid out
appropriately. Also, removed
items will
be returned from the scrap to help determine correct placement of other items.
These removed items should not be added to the child list, but should be used
to help calculate correct positioning of other views, including views that
were not previously onscreen (referred to as APPEARING views), but whose
pre-layout offscreen position can be determined given the extra
information about the pre-layout removed views.
The second layout pass is the real layout in which only non-removed views
will be used. The only additional requirement during this pass is, if
supportsPredictiveItemAnimations()
returns true, to note which
views exist in the child list prior to layout and which are not there after
layout (referred to as DISAPPEARING views), and to position/layout those views
appropriately, without regard to the actual bounds of the RecyclerView. This allows
the animation system to know the location to which to animate these disappearing
views.
The default LayoutManager implementations for RecyclerView handle all of these requirements for animations already. Clients of RecyclerView can either use one of these layout managers directly or look at their implementations of onLayoutChildren() to see how they account for the APPEARING and DISAPPEARING views.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : Recycler to use for fetching potentially cached views for a
position |
state |
RecyclerView.State : Transient state of RecyclerView
|
onLayoutCompleted
void onLayoutCompleted (RecyclerView.State state)
Called after a full layout calculation is finished. The layout calculation may include
multiple onLayoutChildren(Recycler, State)
calls due to animations or
layout measurement but it will include only one onLayoutCompleted(State)
call.
This method will be called at the end of layout(int, int, int, int)
call.
This is a good place for the LayoutManager to do some cleanup like pending scroll position, saved state etc.
Parameters | |
---|---|
state |
RecyclerView.State : Transient state of RecyclerView
|
onMeasure
void onMeasure (RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec)
Measure the attached RecyclerView. Implementations must call
setMeasuredDimension(int, int)
before returning.
It is strongly advised to use the AutoMeasure mechanism by overriding
isAutoMeasureEnabled()
to return true as AutoMeasure handles all the standard
measure cases including when the RecyclerView's layout_width or layout_height have been
set to wrap_content. If isAutoMeasureEnabled()
is overridden to return true,
this method should not be overridden.
The default implementation will handle EXACTLY measurements and respect the minimum width and height properties of the host RecyclerView if measured as UNSPECIFIED. AT_MOST measurements will be treated as EXACTLY and the RecyclerView will consume all available space.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : Recycler |
state |
RecyclerView.State : Transient state of RecyclerView |
widthSpec |
int : Width View.MeasureSpec |
heightSpec |
int : Height View.MeasureSpec |
onRequestChildFocus
boolean onRequestChildFocus (RecyclerView parent, View child, View focused)
This method was deprecated
in API level 22.1.0.
Use onRequestChildFocus(RecyclerView, State, View, View)
Parameters | |
---|---|
parent |
RecyclerView |
child |
View |
focused |
View |
Returns | |
---|---|
boolean |
onRequestChildFocus
boolean onRequestChildFocus (RecyclerView parent, RecyclerView.State state, View child, View focused)
Called when a descendant view of the RecyclerView requests focus.
A LayoutManager wishing to keep focused views aligned in a specific portion of the view may implement that behavior in an override of this method.
If the LayoutManager executes different behavior that should override the default behavior of scrolling the focused child on screen instead of running alongside it, this method should return true.
Parameters | |
---|---|
parent |
RecyclerView : The RecyclerView hosting this LayoutManager |
state |
RecyclerView.State : Current state of RecyclerView |
child |
View : Direct child of the RecyclerView containing the newly focused view |
focused |
View : The newly focused view. This may be the same view as child or it may be
null |
Returns | |
---|---|
boolean |
true if the default scroll behavior should be suppressed |
onRestoreInstanceState
void onRestoreInstanceState (Parcelable state)
Parameters | |
---|---|
state |
Parcelable |
onSaveInstanceState
Parcelable onSaveInstanceState ()
Called when the LayoutManager should save its state. This is a good time to save your scroll position, configuration and anything else that may be required to restore the same layout state if the LayoutManager is recreated.
RecyclerView does NOT verify if the LayoutManager has changed between state save and restore. This will let you share information between your LayoutManagers but it is also your responsibility to make sure they use the same parcelable class.
Returns | |
---|---|
Parcelable |
Necessary information for LayoutManager to be able to restore its state |
onScrollStateChanged
void onScrollStateChanged (int state)
RecyclerView calls this method to notify LayoutManager that scroll state has changed.
Parameters | |
---|---|
state |
int : The new scroll state for RecyclerView
|
performAccessibilityAction
boolean performAccessibilityAction (RecyclerView.Recycler recycler, RecyclerView.State state, int action, Bundle args)
Called by AccessibilityDelegate when an action is requested from the RecyclerView.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
action |
int : The action to perform |
args |
Bundle : Optional action arguments |
Returns | |
---|---|
boolean |
performAccessibilityActionForItem
boolean performAccessibilityActionForItem (RecyclerView.Recycler recycler, RecyclerView.State state, View view, int action, Bundle args)
Called by AccessibilityDelegate when an accessibility action is requested on one of the children of LayoutManager.
Default implementation does not do anything.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : The Recycler that can be used to convert view positions into adapter
positions |
state |
RecyclerView.State : The current state of RecyclerView |
view |
View : The child view on which the action is performed |
action |
int : The action to perform |
args |
Bundle : Optional action arguments |
Returns | |
---|---|
boolean |
true if action is handled |
postOnAnimation
void postOnAnimation (Runnable action)
Causes the Runnable to execute on the next animation time step. The runnable will be run on the user interface thread.
Calling this method when LayoutManager is not attached to a RecyclerView has no effect.
Parameters | |
---|---|
action |
Runnable : The Runnable that will be executed. |
See also:
removeAllViews
void removeAllViews ()
Remove all views from the currently attached RecyclerView. This will not recycle any of the affected views; the LayoutManager is responsible for doing so if desired.
removeAndRecycleAllViews
void removeAndRecycleAllViews (RecyclerView.Recycler recycler)
Removes all views and recycles them using the given recycler.
If you want to clean cached views as well, you should call clear()
too.
If a View is marked as "ignored", it is not removed nor recycled.
Parameters | |
---|---|
recycler |
RecyclerView.Recycler : Recycler to use to recycle children |
removeAndRecycleView
void removeAndRecycleView (View child, RecyclerView.Recycler recycler)
Remove a child view and recycle it using the given Recycler.
Parameters | |
---|---|
child |
View : Child to remove and recycle |
recycler |
RecyclerView.Recycler : Recycler to use to recycle child
|
removeAndRecycleViewAt
void removeAndRecycleViewAt (int index, RecyclerView.Recycler recycler)
Remove a child view and recycle it using the given Recycler.
Parameters | |
---|---|
index |
int : Index of child to remove and recycle |
recycler |
RecyclerView.Recycler : Recycler to use to recycle child
|
removeCallbacks
boolean removeCallbacks (Runnable action)
Removes the specified Runnable from the message queue.
Calling this method when LayoutManager is not attached to a RecyclerView has no effect.
Parameters | |
---|---|
action |
Runnable : The Runnable to remove from the message handling queue |
Returns | |
---|---|
boolean |
true if RecyclerView could ask the Handler to remove the Runnable, false otherwise. When the returned value is true, the Runnable may or may not have been actually removed from the message queue (for instance, if the Runnable was not in the queue already.) |
See also:
removeDetachedView
void removeDetachedView (View child)
Finish removing a view that was previously temporarily
detached
.
Parameters | |
---|---|
child |
View : Detached child to remove
|
removeView
void removeView (View child)
Remove a view from the currently attached RecyclerView if needed. LayoutManagers should
use this method to completely remove a child view that is no longer needed.
LayoutManagers should strongly consider recycling removed views using
recycleView(android.view.View)
.
Parameters | |
---|---|
child |
View : View to remove
|
removeViewAt
void removeViewAt (int index)
Remove a view from the currently attached RecyclerView if needed. LayoutManagers should
use this method to completely remove a child view that is no longer needed.
LayoutManagers should strongly consider recycling removed views using
recycleView(android.view.View)
.
Parameters | |
---|---|
index |
int : Index of the child view to remove
|
requestChildRectangleOnScreen
boolean requestChildRectangleOnScreen (RecyclerView parent, View child, Rect rect, boolean immediate, boolean focusedChildVisible)
Requests that the given child of the RecyclerView be positioned onto the screen. This method can be called for both unfocusable and focusable child views. For unfocusable child views, focusedChildVisible is typically true in which case, layout manager makes the child view visible only if the currently focused child stays in-bounds of RV.
Parameters | |
---|---|
parent |
RecyclerView : The parent RecyclerView. |
child |
View : The direct child making the request. |
rect |
Rect : The rectangle in the child's coordinates the child
wishes to be on the screen. |
immediate |
boolean : True to forbid animated or delayed scrolling,
false otherwise |
focusedChildVisible |
boolean : Whether the currently focused view must stay visible. |
Returns | |
---|---|
boolean |
Whether the group scrolled to handle the operation |
requestChildRectangleOnScreen
boolean requestChildRectangleOnScreen (RecyclerView parent, View child, Rect rect, boolean immediate)
Called when a child of the RecyclerView wants a particular rectangle to be positioned
onto the screen. See requestChildRectangleOnScreen(android.view.View, android.graphics.Rect, boolean)
for more details.
The base implementation will attempt to perform a standard programmatic scroll to bring the given rect into view, within the padded area of the RecyclerView.
Parameters | |
---|---|
parent |
RecyclerView |
child |
View : The direct child making the request. |
rect |
Rect : The rectangle in the child's coordinates the child
wishes to be on the screen. |
immediate |
boolean : True to forbid animated or delayed scrolling,
false otherwise |
Returns | |
---|---|
boolean |
Whether the group scrolled to handle the operation |
requestLayout
void requestLayout ()
Calls RecyclerView#requestLayout
on the underlying RecyclerView
requestSimpleAnimationsInNextLayout
void requestSimpleAnimationsInNextLayout ()
A LayoutManager can call this method to force RecyclerView to run simple animations in the next layout pass, even if there is not any trigger to do so. (e.g. adapter data change).
Note that, calling this method will not guarantee that RecyclerView will run animations
at all. For example, if there is not any RecyclerView.ItemAnimator
set, RecyclerView will
not run any animations but will still clear this flag after the layout is complete.
scrollHorizontallyBy
int scrollHorizontallyBy (int dx, RecyclerView.Recycler recycler, RecyclerView.State state)
Scroll horizontally by dx pixels in screen coordinates and return the distance traveled. The default implementation does nothing and returns 0.
Parameters | |
---|---|
dx |
int : distance to scroll by in pixels. X increases as scroll position
approaches the right. |
recycler |
RecyclerView.Recycler : Recycler to use for fetching potentially cached views for a
position |
state |
RecyclerView.State : Transient state of RecyclerView |
Returns | |
---|---|
int |
The actual distance scrolled. The return value will be negative if dx was
negative and scrolling proceeeded in that direction.
Math.abs(result) may be less than dx if a boundary was reached.
|
scrollToPosition
void scrollToPosition (int position)
Scroll to the specified adapter position. Actual position of the item on the screen depends on the LayoutManager implementation.
Parameters | |
---|---|
position |
int : Scroll to this adapter position.
|
scrollVerticallyBy
int scrollVerticallyBy (int dy, RecyclerView.Recycler recycler, RecyclerView.State state)
Scroll vertically by dy pixels in screen coordinates and return the distance traveled. The default implementation does nothing and returns 0.
Parameters | |
---|---|
dy |
int : distance to scroll in pixels. Y increases as scroll position
approaches the bottom. |
recycler |
RecyclerView.Recycler : Recycler to use for fetching potentially cached views for a
position |
state |
RecyclerView.State : Transient state of RecyclerView |
Returns | |
---|---|
int |
The actual distance scrolled. The return value will be negative if dy was
negative and scrolling proceeeded in that direction.
Math.abs(result) may be less than dy if a boundary was reached.
|
setAutoMeasureEnabled
void setAutoMeasureEnabled (boolean enabled)
This method was deprecated
in API level 27.1.0.
Implementors of LayoutManager should define whether or not it uses
AutoMeasure by overriding isAutoMeasureEnabled()
.
Defines whether the measuring pass of layout should use the AutoMeasure mechanism of
RecyclerView
or if it should be done by the LayoutManager's implementation of
onMeasure(Recycler, State, int, int)
.
Parameters | |
---|---|
enabled |
boolean : True if layout measurement should be done by the
RecyclerView, false if it should be done by this
LayoutManager. |
See also:
setItemPrefetchEnabled
void setItemPrefetchEnabled (boolean enabled)
Sets whether the LayoutManager should be queried for views outside of its viewport while the UI thread is idle between frames.
If enabled, the LayoutManager will be queried for items to inflate/bind in between view system traversals on devices running API 21 or greater. Default value is true.
On platforms API level 21 and higher, the UI thread is idle between passing a frame to RenderThread and the starting up its next frame at the next VSync pulse. By prefetching out of window views in this time period, delays from inflation and view binding are much less likely to cause jank and stuttering during scrolls and flings.
While prefetch is enabled, it will have the side effect of expanding the effective size of the View cache to hold prefetched views.
Parameters | |
---|---|
enabled |
boolean : True if items should be prefetched in between traversals. |
See also:
setMeasuredDimension
void setMeasuredDimension (int widthSize, int heightSize)
Set the measured dimensions
of the
host RecyclerView.
Parameters | |
---|---|
widthSize |
int : Measured width |
heightSize |
int : Measured height
|
setMeasuredDimension
void setMeasuredDimension (Rect childrenBounds, int wSpec, int hSpec)
Sets the measured dimensions from the given bounding box of the children and the
measurement specs that were passed into onMeasure(int, int)
. It is
only called if a LayoutManager returns true
from
isAutoMeasureEnabled()
and it is called after the RecyclerView calls
onLayoutChildren(Recycler, State)
in the execution of
onMeasure(int, int)
.
This method must call setMeasuredDimension(int, int)
.
The default implementation adds the RecyclerView's padding to the given bounding box then caps the value to be within the given measurement specs.
Parameters | |
---|---|
childrenBounds |
Rect : The bounding box of all children |
wSpec |
int : The widthMeasureSpec that was passed into the RecyclerView. |
hSpec |
int : The heightMeasureSpec that was passed into the RecyclerView. |
setMeasurementCacheEnabled
void setMeasurementCacheEnabled (boolean measurementCacheEnabled)
Sets whether RecyclerView should use its own measurement cache for the children. This is a more aggressive cache than the framework uses.
Parameters | |
---|---|
measurementCacheEnabled |
boolean : True to enable the measurement cache, false otherwise. |
See also:
smoothScrollToPosition
void smoothScrollToPosition (RecyclerView recyclerView, RecyclerView.State state, int position)
Smooth scroll to the specified adapter position.
To support smooth scrolling, override this method, create your RecyclerView.SmoothScroller
instance and call startSmoothScroll(SmoothScroller)
.
Parameters | |
---|---|
recyclerView |
RecyclerView : The RecyclerView to which this layout manager is attached |
state |
RecyclerView.State : Current State of RecyclerView |
position |
int : Scroll to this adapter position.
|
startSmoothScroll
void startSmoothScroll (RecyclerView.SmoothScroller smoothScroller)
Starts a smooth scroll using the provided SmoothScroller.
Calling this method will cancel any previous smooth scroll request.
Parameters | |
---|---|
smoothScroller |
RecyclerView.SmoothScroller : Instance which defines how smooth scroll should be animated
|
stopIgnoringView
void stopIgnoringView (View view)
View can be scrapped and recycled again.
Note that calling this method removes all information in the view holder.
You can call this method only if your LayoutManger is in onLayout or onScroll callback.
Parameters | |
---|---|
view |
View : View to ignore.
|
supportsPredictiveItemAnimations
boolean supportsPredictiveItemAnimations ()
Returns whether this LayoutManager supports "predictive item animations".
"Predictive item animations" are automatically created animations that show where items came from, and where they are going to, as items are added, removed, or moved within a layout.
A LayoutManager wishing to support predictive item animations must override this
method to return true (the default implementation returns false) and must obey certain
behavioral contracts outlined in onLayoutChildren(Recycler, State)
.
Whether item animations actually occur in a RecyclerView is actually determined by both
the return value from this method and the
ItemAnimator
set on the
RecyclerView itself. If the RecyclerView has a non-null ItemAnimator but this
method returns false, then only "simple item animations" will be enabled in the
RecyclerView, in which views whose position are changing are simply faded in/out. If the
RecyclerView has a non-null ItemAnimator and this method returns true, then predictive
item animations will be enabled in the RecyclerView.
Returns | |
---|---|
boolean |
true if this LayoutManager supports predictive item animations, false otherwise. |
Annotations
Interfaces
- ActionMenuView.OnMenuItemClickListener
- PopupMenu.OnDismissListener
- PopupMenu.OnMenuItemClickListener
- RecyclerView.ChildDrawingOrderCallback
- RecyclerView.ItemAnimator.ItemAnimatorFinishedListener
- RecyclerView.LayoutManager.LayoutPrefetchRegistry
- RecyclerView.OnChildAttachStateChangeListener
- RecyclerView.OnItemTouchListener
- RecyclerView.RecyclerListener
- RecyclerView.SmoothScroller.ScrollVectorProvider
- SearchView.OnCloseListener
- SearchView.OnQueryTextListener
- SearchView.OnSuggestionListener
- ShareActionProvider.OnShareTargetSelectedListener
- ThemedSpinnerAdapter
- Toolbar.OnMenuItemClickListener
Classes
- ActionMenuView
- ActionMenuView.LayoutParams
- AppCompatAutoCompleteTextView
- AppCompatButton
- AppCompatCheckBox
- AppCompatCheckedTextView
- AppCompatEditText
- AppCompatImageButton
- AppCompatImageView
- AppCompatMultiAutoCompleteTextView
- AppCompatRadioButton
- AppCompatRatingBar
- AppCompatSeekBar
- AppCompatSpinner
- AppCompatTextView
- CardView
- DefaultItemAnimator
- DividerItemDecoration
- GridLayout
- GridLayout.Alignment
- GridLayout.LayoutParams
- GridLayout.Spec
- GridLayoutManager
- GridLayoutManager.DefaultSpanSizeLookup
- GridLayoutManager.LayoutParams
- GridLayoutManager.SpanSizeLookup
- LinearLayoutCompat
- LinearLayoutCompat.LayoutParams
- LinearLayoutManager
- LinearLayoutManager.LayoutChunkResult
- LinearSmoothScroller
- LinearSnapHelper
- ListPopupWindow
- OrientationHelper
- PagerSnapHelper
- PopupMenu
- RecyclerView
- RecyclerView.Adapter
- RecyclerView.AdapterDataObserver
- RecyclerView.EdgeEffectFactory
- RecyclerView.ItemAnimator
- RecyclerView.ItemAnimator.ItemHolderInfo
- RecyclerView.ItemDecoration
- RecyclerView.LayoutManager
- RecyclerView.LayoutManager.Properties
- RecyclerView.LayoutParams
- RecyclerView.OnFlingListener
- RecyclerView.OnScrollListener
- RecyclerView.RecycledViewPool
- RecyclerView.Recycler
- RecyclerView.SimpleOnItemTouchListener
- RecyclerView.SmoothScroller
- RecyclerView.SmoothScroller.Action
- RecyclerView.State
- RecyclerView.ViewCacheExtension
- RecyclerView.ViewHolder
- RecyclerViewAccessibilityDelegate
- RecyclerViewAccessibilityDelegate.ItemDelegate
- SearchView
- ShareActionProvider
- SimpleItemAnimator
- SnapHelper
- StaggeredGridLayoutManager
- StaggeredGridLayoutManager.LayoutParams
- SwitchCompat
- ThemedSpinnerAdapter.Helper
- Toolbar
- Toolbar.LayoutParams
- Toolbar.SavedState
- TooltipCompat
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Last updated 2024-04-11 UTC.