belongs to Maven artifact com.android.support:recyclerview-v7:28.0.0-alpha1
StaggeredGridLayoutManager
public
class
StaggeredGridLayoutManager
extends RecyclerView.LayoutManager
implements
RecyclerView.SmoothScroller.ScrollVectorProvider
java.lang.Object | ||
↳ | android.support.v7.widget.RecyclerView.LayoutManager | |
↳ | android.support.v7.widget.StaggeredGridLayoutManager |
A LayoutManager that lays out children in a staggered grid formation. It supports horizontal & vertical layout as well as an ability to layout children in reverse.
Staggered grids are likely to have gaps at the edges of the layout. To avoid these gaps,
StaggeredGridLayoutManager can offset spans independently or move items between spans. You can
control this behavior via setGapStrategy(int)
.
Summary
Nested classes | |
---|---|
class |
StaggeredGridLayoutManager.LayoutParams
LayoutParams used by StaggeredGridLayoutManager. |
Inherited XML attributes | |
---|---|
From
class
android.support.v7.widget.RecyclerView.LayoutManager
|
Constants | |
---|---|
int |
GAP_HANDLING_LAZY
This constant was deprecated in API level 22.1.0. No longer supported. |
int |
GAP_HANDLING_MOVE_ITEMS_BETWEEN_SPANS
When scroll state is changed to |
int |
GAP_HANDLING_NONE
Does not do anything to hide gaps. |
int |
HORIZONTAL
|
int |
VERTICAL
|
Public constructors | |
---|---|
StaggeredGridLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
Constructor used when layout manager is set in XML by RecyclerView attribute "layoutManager". |
|
StaggeredGridLayoutManager(int spanCount, int orientation)
Creates a StaggeredGridLayoutManager with given parameters. |
Public methods | |
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void
|
assertNotInLayoutOrScroll(String message)
Checks if RecyclerView is in the middle of a layout or scroll and throws an
|
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. |
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. |
PointF
|
computeScrollVectorForPosition(int targetPosition)
Should calculate the vector that points to the direction where the target position can be found. |
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. |
int[]
|
findFirstCompletelyVisibleItemPositions(int[] into)
Returns the adapter position of the first completely visible view for each span. |
int[]
|
findFirstVisibleItemPositions(int[] into)
Returns the adapter position of the first visible view for each span. |
int[]
|
findLastCompletelyVisibleItemPositions(int[] into)
Returns the adapter position of the last completely visible view for each span. |
int[]
|
findLastVisibleItemPositions(int[] into)
Returns the adapter position of the last visible view for each span. |
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
|
getColumnCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the number of columns for accessibility. |
int
|
getGapStrategy()
Returns the current gap handling strategy for StaggeredGridLayoutManager. |
int
|
getOrientation()
|
boolean
|
getReverseLayout()
Returns whether views are laid out in reverse order or not. |
int
|
getRowCountForAccessibility(RecyclerView.Recycler recycler, RecyclerView.State state)
Returns the number of rows for accessibility. |
int
|
getSpanCount()
Returns the number of spans laid out by StaggeredGridLayoutManager. |
void
|
invalidateSpanAssignments()
For consistency, StaggeredGridLayoutManager keeps a mapping between spans and items. |
boolean
|
isAutoMeasureEnabled()
Returns whether the measuring pass of layout should use the AutoMeasure mechanism of
|
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
|
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. |
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
|
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. |
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, 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
|
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. |
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. |
void
|
scrollToPositionWithOffset(int position, int offset)
Scroll to the specified adapter position with the given offset from layout start. |
int
|
scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state)
Scroll vertically by dy pixels in screen coordinates and return the distance traveled. |
void
|
setGapStrategy(int gapStrategy)
Sets the gap handling strategy for StaggeredGridLayoutManager. |
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
|
setOrientation(int orientation)
Sets the orientation of the layout. |
void
|
setReverseLayout(boolean reverseLayout)
Sets whether LayoutManager should start laying out items from the end of the UI. |
void
|
setSpanCount(int spanCount)
Sets the number of spans for the layout. |
void
|
smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position)
Smooth scroll to the specified adapter position. |
boolean
|
supportsPredictiveItemAnimations()
Returns whether this LayoutManager supports "predictive item animations". |
Inherited methods | |
---|---|
From
class
android.support.v7.widget.RecyclerView.LayoutManager
| |
From
class
java.lang.Object
| |
From
interface
android.support.v7.widget.RecyclerView.SmoothScroller.ScrollVectorProvider
|
Constants
GAP_HANDLING_LAZY
int GAP_HANDLING_LAZY
This constant was deprecated
in API level 22.1.0.
No longer supported.
Constant Value: 1 (0x00000001)
GAP_HANDLING_MOVE_ITEMS_BETWEEN_SPANS
int GAP_HANDLING_MOVE_ITEMS_BETWEEN_SPANS
When scroll state is changed to SCROLL_STATE_IDLE
, StaggeredGrid will
check if there are gaps in the because of full span items. If it finds, it will re-layout
and move items to correct positions with animations.
For example, if LayoutManager ends up with the following layout due to adapter changes:
AAA _BC DDD
It will animate to the following state:
AAA BC_ DDD
Constant Value: 2 (0x00000002)
GAP_HANDLING_NONE
int GAP_HANDLING_NONE
Does not do anything to hide gaps.
Constant Value: 0 (0x00000000)
Public constructors
StaggeredGridLayoutManager
StaggeredGridLayoutManager (Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
Constructor used when layout manager is set in XML by RecyclerView attribute "layoutManager". Defaults to single column and vertical.
Parameters | |
---|---|
context |
Context |
attrs |
AttributeSet |
defStyleAttr |
int |
defStyleRes |
int |
StaggeredGridLayoutManager
StaggeredGridLayoutManager (int spanCount, int orientation)
Creates a StaggeredGridLayoutManager with given parameters.
Parameters | |
---|---|
spanCount |
int : If orientation is vertical, spanCount is number of columns. If
orientation is horizontal, spanCount is number of rows. |
orientation |
int : VERTICAL or HORIZONTAL
|
Public methods
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. |
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 |
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 |
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 |
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 |
computeScrollVectorForPosition
PointF computeScrollVectorForPosition (int targetPosition)
Should calculate the vector that points to the direction where the target position can be found.
This method is used by the LinearSmoothScroller
to initiate a scroll towards
the target position.
The magnitude of the vector is not important. It is always normalized before being
used by the LinearSmoothScroller
.
LayoutManager should not check whether the position exists in the adapter or not.
Parameters | |
---|---|
targetPosition |
int : the target position to which the returned vector should point |
Returns | |
---|---|
PointF |
the scroll vector for a given position. |
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 |
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 |
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 |
findFirstCompletelyVisibleItemPositions
int[] findFirstCompletelyVisibleItemPositions (int[] into)
Returns the adapter position of the first completely visible view for each span.
Note that, this value is not affected by layout orientation or item order traversal.
(setReverseLayout(boolean)
). Views are sorted by their positions in the adapter,
not in the layout.
If RecyclerView has item decorators, they will be considered in calculations as well.
StaggeredGridLayoutManager may pre-cache some views that are not necessarily visible. Those views are ignored in this method.
Parameters | |
---|---|
into |
int : An array to put the results into. If you don't provide any, LayoutManager will
create a new one. |
Returns | |
---|---|
int[] |
The adapter position of the first fully visible item in each span. If a span does
not have any items, NO_POSITION is returned for that span. |
findFirstVisibleItemPositions
int[] findFirstVisibleItemPositions (int[] into)
Returns the adapter position of the first visible view for each span.
Note that, this value is not affected by layout orientation or item order traversal.
(setReverseLayout(boolean)
). Views are sorted by their positions in the adapter,
not in the layout.
If RecyclerView has item decorators, they will be considered in calculations as well.
StaggeredGridLayoutManager may pre-cache some views that are not necessarily visible. Those views are ignored in this method.
Parameters | |
---|---|
into |
int : An array to put the results into. If you don't provide any, LayoutManager will
create a new one. |
Returns | |
---|---|
int[] |
The adapter position of the first visible item in each span. If a span does not have
any items, NO_POSITION is returned for that span. |
findLastCompletelyVisibleItemPositions
int[] findLastCompletelyVisibleItemPositions (int[] into)
Returns the adapter position of the last completely visible view for each span.
Note that, this value is not affected by layout orientation or item order traversal.
(setReverseLayout(boolean)
). Views are sorted by their positions in the adapter,
not in the layout.
If RecyclerView has item decorators, they will be considered in calculations as well.
StaggeredGridLayoutManager may pre-cache some views that are not necessarily visible. Those views are ignored in this method.
Parameters | |
---|---|
into |
int : An array to put the results into. If you don't provide any, LayoutManager will
create a new one. |
Returns | |
---|---|
int[] |
The adapter position of the last fully visible item in each span. If a span does not
have any items, NO_POSITION is returned for that span. |
findLastVisibleItemPositions
int[] findLastVisibleItemPositions (int[] into)
Returns the adapter position of the last visible view for each span.
Note that, this value is not affected by layout orientation or item order traversal.
(setReverseLayout(boolean)
). Views are sorted by their positions in the adapter,
not in the layout.
If RecyclerView has item decorators, they will be considered in calculations as well.
StaggeredGridLayoutManager may pre-cache some views that are not necessarily visible. Those views are ignored in this method.
Parameters | |
---|---|
into |
int : An array to put the results into. If you don't provide any, LayoutManager will
create a new one. |
Returns | |
---|---|
int[] |
The adapter position of the last visible item in each span. If a span does not have
any items, NO_POSITION is returned for that span. |
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 |
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. |
getGapStrategy
int getGapStrategy ()
Returns the current gap handling strategy for StaggeredGridLayoutManager.
Staggered grid may have gaps in the layout due to changes in the adapter. To avoid gaps,
StaggeredGridLayoutManager provides 2 options. Check GAP_HANDLING_NONE
and
GAP_HANDLING_MOVE_ITEMS_BETWEEN_SPANS
for details.
By default, StaggeredGridLayoutManager uses GAP_HANDLING_MOVE_ITEMS_BETWEEN_SPANS
.
Returns | |
---|---|
int |
Current gap handling strategy. |
getReverseLayout
boolean getReverseLayout ()
Returns whether views are laid out in reverse order or not.
Not that this value is not affected by RecyclerView's layout direction.
Returns | |
---|---|
boolean |
True if layout is reversed, false otherwise |
See also:
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. |
getSpanCount
int getSpanCount ()
Returns the number of spans laid out by StaggeredGridLayoutManager.
Returns | |
---|---|
int |
Number of spans in the layout |
invalidateSpanAssignments
void invalidateSpanAssignments ()
For consistency, StaggeredGridLayoutManager keeps a mapping between spans and items.
If you need to cancel current assignments, you can call this method which will clear all assignments and request a new layout.
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) . |
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
|
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. |
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 |
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 |
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, 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
|
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
|
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.
|
scrollToPositionWithOffset
void scrollToPositionWithOffset (int position, int offset)
Scroll to the specified adapter position with the given offset from layout start.
Note that scroll position change will not be reflected until the next layout call.
If you are just trying to make a position visible, use scrollToPosition(int)
.
Parameters | |
---|---|
position |
int : Index (starting at 0) of the reference item. |
offset |
int : The distance (in pixels) between the start edge of the item view and
start edge of the RecyclerView. |
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.
|
setGapStrategy
void setGapStrategy (int gapStrategy)
Sets the gap handling strategy for StaggeredGridLayoutManager. If the gapStrategy parameter is different than the current strategy, calling this method will trigger a layout request.
Parameters | |
---|---|
gapStrategy |
int : The new gap handling strategy. Should be
GAP_HANDLING_MOVE_ITEMS_BETWEEN_SPANS or GAP_HANDLING_NONE . |
See also:
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. |
setOrientation
void setOrientation (int orientation)
Sets the orientation of the layout. StaggeredGridLayoutManager will do its best to keep scroll position if this method is called after views are laid out.
Parameters | |
---|---|
orientation |
int : HORIZONTAL or VERTICAL
|
setReverseLayout
void setReverseLayout (boolean reverseLayout)
Sets whether LayoutManager should start laying out items from the end of the UI. The order items are traversed is not affected by this call.
For vertical layout, if it is set to true
, first item will be at the bottom of
the list.
For horizontal layouts, it depends on the layout direction.
When set to true, If RecyclerView
is LTR, than it will layout from RTL, if
RecyclerView
} is RTL, it will layout from LTR.
Parameters | |
---|---|
reverseLayout |
boolean : Whether layout should be in reverse or not
|
setSpanCount
void setSpanCount (int spanCount)
Sets the number of spans for the layout. This will invalidate all of the span assignments for Views.
Calling this method will automatically result in a new layout request unless the spanCount parameter is equal to current span count.
Parameters | |
---|---|
spanCount |
int : Number of spans to layout
|
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.
|
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.