@Override
  public void onVisibilityChange(boolean isVisible) {
    if (mIsVisible == isVisible) {
      return;
    }
    mEventTracker.recordEvent(isVisible ? Event.ON_DRAWABLE_SHOW : Event.ON_DRAWABLE_HIDE);
    mIsVisible = isVisible;
    attachOrDetachController();
  }
Callback used to notify about top-level-drawable's visibility changes.
drawee/src/main/java/com/facebook/drawee/view/DraweeHolder.java