findViewById() returns null for custom component in layout XML, not for other components

Question

I have a res/layout/main.xml including these elements and others:

Answer 1

This happened to me with a custom component for Wear, but is a generic piece of advice. If you're using a Stub (such as I was using WatchViewStub), you can't just put the call to findViewById() anywhere. Everything inside the stub must be inflated first, which doesn't just happen after setContentView(). Thus, you should write something like this in order to wait for that to happen:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_wear);
    final WatchViewStub stub = (WatchViewStub) findViewById(R.id.watch_view_stub);
    stub.setOnLayoutInflatedListener(new WatchViewStub.OnLayoutInflatedListener() {
        @Override
        public void onLayoutInflated(WatchViewStub stub) {
            myCustomViewInst = (MyCustomView) findViewById(R.id.my_custom_view);
            ...