Allow to detect Ambient mode to switch Watch face display on Wear devices

Watch face Ambient mode detection

Handler handler = new Handler(Looper.getMainLooper());

final DisplayManager displayManager = (DisplayManager) getSystemService(Context.DISPLAY_SERVICE);
displayManager.registerDisplayListener(new DisplayManager.DisplayListener() {
    @Override
    public void onDisplayAdded(int displayId) {

    }

    @Override
    public void onDisplayRemoved(int displayId) {

    }

    @Override
    public void onDisplayChanged(int displayId) {
        try {
            if (displayManager.getDisplay(displayId).getState() == Display.STATE_DOZING) {
                updateFaceDisplay(true);
                Log.d(TAG, "onDisplayChanged: dozing");
            } else {
                updateFaceDisplay(false);
                Log.d(TAG, "onDisplayChanged: not dozing");
    
            }
        } catch (NullPointerException exception) {
        }
    }
}, handler);

You can set the Handler to null, unless you do this outside of the UI thread

So, I went to add this to my sample app and noticed something. The listener needs to be unregistered at some point, or even after the watch face is gone (switching watch faces), it will continue to call all of the methods.

Any particular reason why you are catching/ignoring the NullPointerException here?

try {
    ...
} catch (NullPointerException e) {
}

@kentarosu onDestroy() is the perfect place to unregister 😉