Add spinners to your app

Spinners provide a quick way to select one value from a set. In the default state, a spinner shows its currently selected value. Tapping the spinner displays a menu showing all other values the user can select.

You can add a spinner to your layout with the Spinner object, which you usually do in your XML layout with a <Spinner> element. This is shown in the following example:

<Spinner
    android:id="@+id/planets_spinner"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

To populate the spinner with a list of choices, specify a SpinnerAdapter in your Activity or Fragment source code.

If you are using Material Design Components, exposed dropdown menus are the equivalent of a Spinner.

Populate the spinner with user choices

The choices you provide for the spinner can come from any source, but you must provide them through a SpinnerAdapter, such as an ArrayAdapter if the choices are available in an array or a CursorAdapter if the choices are available from a database query.

For example, if the available choices for your spinner are pre-determined, you can provide them with a string array defined in a string resource file:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="planets_array">
        <item>Mercury</item>
        <item>Venus</item>
        <item>Earth</item>
        <item>Mars</item>
        <item>Jupiter</item>
        <item>Saturn</item>
        <item>Uranus</item>
        <item>Neptune</item>
    </string-array>
</resources>

With an array like this, you can use the following code in your Activity or Fragment to supply the spinner with the array using an instance of ArrayAdapter:

val spinner: Spinner = findViewById(R.id.planets_spinner)
// Create an ArrayAdapter using the string array and a default spinner layout.
ArrayAdapter.createFromResource(
        this,
        R.array.planets_array,
        android.R.layout.simple_spinner_item
).also { adapter ->
    // Specify the layout to use when the list of choices appears.
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
    // Apply the adapter to the spinner.
    spinner.adapter = adapter
}

Spinner spinner = (Spinner) findViewById(R.id.planets_spinner);
// Create an ArrayAdapter using the string array and a default spinner layout.
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
        this,
        R.array.planets_array,
        android.R.layout.simple_spinner_item
);
// Specify the layout to use when the list of choices appears.
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner.
spinner.setAdapter(adapter);

The createFromResource() method lets you create an ArrayAdapter from the string array. The third argument for this method is a layout resource that defines how the selected choice appears in the spinner control. The platform provides the simple_spinner_item layout. This is the default layout unless you want to define your own layout for the spinner's appearance.

Call setDropDownViewResource(int) to specify the layout the adapter uses to display the list of spinner choices. simple_spinner_dropdown_item is another standard layout defined by the platform.

Call setAdapter() to apply the adapter to your Spinner.

Respond to user selections

When the user selects an item from the spinner's menu, the Spinner object receives an on-item-selected event.

To define the selection event handler for a spinner, implement the AdapterView.OnItemSelectedListener interface and the corresponding onItemSelected() callback method. For example, here's an implementation of the interface in an Activity:

class SpinnerActivity : Activity(), AdapterView.OnItemSelectedListener {
    ...
    override fun onItemSelected(parent: AdapterView<*>, view: View?, pos: Int, id: Long) {
        // An item is selected. You can retrieve the selected item using
        // parent.getItemAtPosition(pos).
    }

    override fun onNothingSelected(parent: AdapterView<*>) {
        // Another interface callback.
    }
}

public class SpinnerActivity extends Activity implements OnItemSelectedListener {
    ...
    public void onItemSelected(AdapterView<?> parent, View view,
            int pos, long id) {
        // An item is selected. You can retrieve the selected item using
        // parent.getItemAtPosition(pos).
    }

    public void onNothingSelected(AdapterView<?> parent) {
        // Another interface callback.
    }
}

The AdapterView.OnItemSelectedListener interface requires the onItemSelected() and onNothingSelected() callback methods.

Specify the interface implementation by calling setOnItemSelectedListener():

val spinner: Spinner = findViewById(R.id.planets_spinner)
spinner.onItemSelectedListener = this

Spinner spinner = (Spinner) findViewById(R.id.planets_spinner);
spinner.setOnItemSelectedListener(this);

If you implement the AdapterView.OnItemSelectedListener interface with your Activity or Fragment, as in the preceding example, you can pass this as the interface instance.