java - ImageView.getWidth() returns 0

Question

I get imageView's width 0. Below is code.

xml file :

<ImageView
        android:id="@+id/img"
        android:layout_width="200dp"
        android:layout_height="200dp" />

Activity :

@Override
protected void onResume() {
    super.onResume();
    ImageView img = (ImageView) findViewById(R.id.img);
    Log.d(TAG, "width : " + img.getWidth());
}

I don't want to use below code as I need to place this code in so many places.

ViewTreeObserver vto = img.getViewTreeObserver();
    vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
        public boolean onPreDraw() {
            ImageView img = (ImageView) findViewById(R.id.img);
                    Log.d(TAG, "width : " + img.getWidth());
            return true;
        }
    });

My workaround : I actually later did not need to add this code in an activity. I added it to a non-activity class and instead of ImageView's width I used Bitmap image's width and now does not have this problem.

Answer 1

Where you calling getWidth() and getHeight() on ImageView? If you calling from onCreate() in activity, it won't work. You need to wait for activity window to attached and then call getWidth() and getHeight() on ImageView. You can try calling getWidth() and getHeight() from onWindowFocusChanged() method of your activity.

call on onWindowFocusChanged like this way

public void onWindowFocusChanged(boolean hasFocus) {
    // TODO Auto-generated method stub
    super.onWindowFocusChanged(hasFocus);
     if (hasFocus) {
        ImageView img = (ImageView) findViewById(R.id.img);
        Log.d(TAG, "width : " + img.getWidth());
     }

    }