android - View getX() and getY() return 0.0 after they have been added to the Activity

Question

In MainActivity onCreate() I instantiated a new View and added it via layout.addView to the activity. If i try getX() or getY() for that view I always get 0.0.

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    RelativeLayout main = (RelativeLayout)findViewById(R.id.main);

    RelativeLayout.LayoutParams squarePosition = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
    GameToken square1 = new GameToken(this,GameToken.SQUARE, fieldHeight,fieldWidth);
    squarePosition.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
    squarePosition.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
    main.addView(square1, squarePosition);
    System.out.println(square1.getX()); //Prints '0.0'
    System.out.println(square1.getY()); //Prints '0.0'

Answer 1

ViewGroups such as RelativeLayout do not layout their children immediately, and thus your View does not yet know where it will lie on screen. You need to wait for the RelativeLayout to complete a layout pass before that can happen.

You can listen for global layout events like so:

view.getViewTreeObserver().addOnGlobalLayoutListener(
    new ViewTreeObserver.OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            // Layout has happened here.

            // Don't forget to remove your listener when you are done with it.
            view.getViewTreeObserver().removeOnGlobalLayoutListener(this);
        }
    });