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Rotary Input

Some Android Wear devices support rotary input, such as a rotating side button (RSB). When the user turns the button, your app's current view should scroll up or down.

If you are using ScrollView, ListView, HorizontalScrollView, or WearableRecyclerView in your app, then your app's view gets rotary input support by default. If you are using custom views other than those listed, or if you want to manually handle rotary input events, see Adding Custom Rotary Input Scrolling.

Focus Best Practices

In order to respond to rotary input events, your scroll view must be in focus. In most cases, this happens automatically; your scrolling view becomes focused immediately after you create your Activity. However, there are situations where you need to manually handle focus of your app's view, such as:

Adding Custom Rotary Input Scrolling

If your scrollable view doesn't natively support rotary input scrolling, or if you want to do something other than scrolling in response to rotary input events (zoom in/out, turn dials, etc.), you can use the RotaryEncoder methods in the Wearable Support Library.

The following code snippet shows how to use RotaryEncoder to add custom scrolling in your app's view:

myView.setOnGenericMotionListener(new View.OnGenericMotionListener() {
    @Override
    public boolean onGenericMotion(View v, MotionEvent ev) {
        if (ev.getAction() == MotionEvent.ACTION_SCROLL && RotaryEncoder.isFromRotaryEncoder(ev)) {
            // Don't forget the negation here
            float delta = -RotaryEncoder.getRotaryAxisValue(ev) * RotaryEncoder.getScaledScrollFactor(
            getContext());

            // Swap these axes if you want to do horizontal scrolling instead
            scrollBy(0, Math.round(delta));

            return true;
        }

        return false;
    }
});

Testing Rotary Input Button on the Emulator

You can use the Android Emulator to simulate rotary input scrolling on a Wear device. Launch your Wear app on the emulator when you run your project, or you can drag an APK file onto the emulator to install it.

To test the rotary input on the emulator:

  1. Get the latest Wear emulator 26.0.1 system image from the Canary channel.
  2. From the SDK manager, use the SDK tools tab to get latest version of the Android Emulator.
  3. Create an AVD (Android Virtual Device) with API 25.

    In Studio, select Tools>Android>AVD Manager. Create a new Wear device with API 25.

  4. Run the emulator from the Android Studio.
  5. Try rotary input scrolling.

    Click the overflow button (three dots at the bottom of the emulator toolbar). Click the Rotary input tab in the new window to open the rotary input interface.

Watch the following video for an overview of how rotary input works on the emulator.

Focus Behavior Tips

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