@Override
    public boolean onTouchEvent(MotionEvent event) {
        //return super.onTouchEvent(event);
        final boolean ret = super.onTouchEvent(event);

        // send to touch drawable
        final TouchEffectDrawable d = mTouchDrawable;
        if (ret && d != null && isEnabled()) {
            d.onTouch(event);
        }

        return ret;
    }
In this, you can set TouchEffectDrawable,
to init TouchEffectDrawable.
<p>
If you not need touch effect,
you should set NULL.
<p>
But, if need it,
you should call {@link TouchEffectDrawable#setEffect(Effect)}

@param touchDrawable TouchEffectDrawable
caprice/ui/src/main/java/net/qiujuer/genius/ui/widget/ImageView.java