@Override
    public void setLayerType(int layerType, Paint paint) {
        // In this, to support Canvas.clipPath(),
        // must set layerType is View.LAYER_TYPE_SOFTWARE
        // on your need touch draw
        if (mTouchDrawable != null)
            layerType = View.LAYER_TYPE_SOFTWARE;
        super.setLayerType(layerType, paint);
    }
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