You’re doing incorrect cast — your background drawable is StateListDrawable
, not AnimationDrawable
. I’d rather do something like:
@Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
btn = (Button)findViewById(R.id.btnAnim);
StateListDrawable background = (StateListDrawable) btn.getBackground();
Drawable current = background.getCurrent();
if (current instanceof AnimationDrawable) {
btnAnimation = (AnimationDrawable) current;
btnAnimation.start();
}
}