FooterPageScreenView.java 文件源码

@TargetApi(21)
void setupDrawables21() {
    AnimatedStateListDrawable drawable = (AnimatedStateListDrawable) mPlayPause.getDrawable();
    drawable.addTransition(R.id.pause_state, R.id.play_state, (AnimatedVectorDrawable)
            ContextCompat.getDrawable(getContext(), R.drawable.vector_pause_play_black_36dp), false);
    drawable.addTransition(R.id.play_state, R.id.pause_state, (AnimatedVectorDrawable)
            ContextCompat.getDrawable(getContext(), R.drawable.vector_play_pause_black_36dp), false);
}