穴の空いたオーバーレイ

gistfile1.java

@Override
protected void dispatchDraw(Canvas canvas) {
	super.dispatchDraw(canvas);

	canvas.saveLayer(null, paint,
			Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
			| Canvas.CLIP_TO_LAYER_SAVE_FLAG);
			
	canvas.drawColor(0x88000000);
	
	Paint paint = new Paint();
	paint.setAntiAlias(true);

	paint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));
	canvas.drawCircle(getWidth()/2, getHeight()/2, getWidth()/2, paint);
	
	canvas.restore();
}