Create lists on Wear OS

Lists let users select an item from a set of choices easily on Wear OS devices.

The Wearable UI Library includes the WearableRecyclerView class, which is a RecyclerView implementation for creating lists optimized for wearable devices. You can use this interface in your wearable app by creating a new WearableRecyclerView container.

Decide whether to use a WearableRecyclerView, based on the kind of user experience you want to provide. We recommend using the WearableRecyclerView for a long list of simple items, such as an application launcher, or a list of contacts. Each item might have a short string and an associated icon. Alternatively, each item might have only a string or an icon.

Note: Avoid complex layouts. Users should only need to glance at an item to understand what it is, especially with wearables' limited screen size.

By extending the existing RecyclerView class, WearableRecyclerView APIs display a vertically scrollable list of items in a straight list by default. You can use the WearableRecyclerView APIs to opt-in for a curved layout and a circular scrolling gesture in your wearable apps.

Figure 1. Default list view on Wear OS.

This lesson shows you how to use the WearableRecyclerView class to create lists in your Wear OS apps. The document also describes how to opt-in for a curved layout for your scrollable items, enable circular scrolling gesture, and customize the appearance of the children while scrolling.

Add WearableRecyclerView to an activity using XML

The following layout (as inserted into, for example, res/layout/activity_main.xml) adds a WearableRecyclerView to an activity, so the list is displayed properly on both round and square devices:

<androidx.wear.widget.WearableRecyclerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/recycler_launcher_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:scrollbars="vertical" />

The following shows the WearableRecyclerView as it could be applied to an activity:

class MainActivity : Activity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }

    ...
}

public class MainActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    ...
}

Create a curved layout

To create a curved layout for scrollable items in your wearable app:

• Use WearableRecyclerView as your main container in the relevant XML layout.
• Set the setEdgeItemsCenteringEnabled(boolean) method to true. This will align the first and last items on the list vertically centered on the screen.
• Use the WearableRecyclerView.setLayoutManager() method to set layout of the items on the screen.

wearableRecyclerView.apply {
    // To align the edge children (first and last) with the center of the screen
    isEdgeItemsCenteringEnabled = true
    ...

    layoutManager = WearableLinearLayoutManager(this@MainActivity)
}

// To align the edge children (first and last) with the center of the screen
wearableRecyclerView.setEdgeItemsCenteringEnabled(true);
...

wearableRecyclerView.setLayoutManager(
                new WearableLinearLayoutManager(this));

If your app has specific requirements to customize the appearance of the children while scrolling (for example, scale the icons and text while the items scroll away from the center), extend the WearableLinearLayoutManager.LayoutCallback class and override the onLayoutFinished method.

The following code snippet shows an example of customizing the scrolling of items to scale farther away from the center by extending the WearableLinearLayoutManager.LayoutCallback class:

/** How much should we scale the icon at most.  */
private const val MAX_ICON_PROGRESS = 0.65f

class CustomScrollingLayoutCallback : WearableLinearLayoutManager.LayoutCallback() {

    private var progressToCenter: Float = 0f

    override fun onLayoutFinished(child: View, parent: RecyclerView) {
        child.apply {
            // Figure out % progress from top to bottom
            val centerOffset = height.toFloat() / 2.0f / parent.height.toFloat()
            val yRelativeToCenterOffset = y / parent.height + centerOffset

            // Normalize for center
            progressToCenter = Math.abs(0.5f - yRelativeToCenterOffset)
            // Adjust to the maximum scale
            progressToCenter = Math.min(progressToCenter, MAX_ICON_PROGRESS)

            scaleX = 1 - progressToCenter
            scaleY = 1 - progressToCenter
        }
    }
}

public class CustomScrollingLayoutCallback extends WearableLinearLayoutManager.LayoutCallback {
    /** How much should we scale the icon at most. */
    private static final float MAX_ICON_PROGRESS = 0.65f;

    private float progressToCenter;

    @Override
    public void onLayoutFinished(View child, RecyclerView parent) {

        // Figure out % progress from top to bottom
        float centerOffset = ((float) child.getHeight() / 2.0f) / (float) parent.getHeight();
        float yRelativeToCenterOffset = (child.getY() / parent.getHeight()) + centerOffset;

        // Normalize for center
        progressToCenter = Math.abs(0.5f - yRelativeToCenterOffset);
        // Adjust to the maximum scale
        progressToCenter = Math.min(progressToCenter, MAX_ICON_PROGRESS);

        child.setScaleX(1 - progressToCenter);
        child.setScaleY(1 - progressToCenter);
    }
}

wearableRecyclerView.layoutManager =
        WearableLinearLayoutManager(this, CustomScrollingLayoutCallback())

CustomScrollingLayoutCallback customScrollingLayoutCallback =
                new CustomScrollingLayoutCallback();
wearableRecyclerView.setLayoutManager(
                new WearableLinearLayoutManager(this, customScrollingLayoutCallback));