@Override
 protected boolean onSetAlpha(int alpha) {
   if (mPrevAlpha != alpha) {
     mPrevAlpha = alpha;
     super.onSetAlpha(alpha);
   }
   return true;
 }
 @Override
 protected boolean onSetAlpha(int alpha) {
   if (mPrevAlpha != alpha) {
     mPrevAlpha = alpha;
     mPaint.setAlpha((int) (alpha * mBubbleColorAlpha));
     super.onSetAlpha(alpha);
   }
   return true;
 }