When is a ConstraintLayout drawn in an Activity?

Question

I have an Android Activity with a ConstraintLayout. I want to get the heights and widths of different views of that ConstraintLayout programatically, but I get 0's because I do it in onCreate() and I guess that the Layout hasn't been drawn yet.

Where should I do it?

Answer 1

int height;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_activity);
    final View myView = findViewById(R.id.myView);
    myView.post(new Runnable(){
        @Override
        public void run() {
            //do the operations related to height here
            //this method is asynchronous
            height = myView.getHeight();
            Log.d(TAG, "Height inside runnable is : "+height); //this will be correct height
        }
    });
    Log.d(TAG, "Height is : "+height); //this will be zero because above method is asynchronous
}

Using the post operation makes sure that the code inside it are called once the view creation is completed.