@Override
    public int getOpacity() {
        if (mState.mEffect == null) {
            return super.getOpacity();
        }
        // not sure, so be safe
        return PixelFormat.TRANSLUCENT;
    }
Called from the drawable's draw() method after the canvas has been set to
draw the shape at (0,0). Subclasses can override for special effects such
as multiple layers, stroking, etc.
caprice/ui/src/main/java/net/qiujuer/genius/ui/drawable/TouchEffectDrawable.java