android clipPath切割画布

（转自：http://wallage.blog.163.com/blog/static/1738962420101012439991/）

public class PictureTestActivity extends Activity {    @Override   public void onCreate(Bundle savedInstanceState){   super.onCreate(savedInstanceState);   setContentView(new SampleView(this));   }    private static class SampleView extends View {        private Paint mPaint;        private Path mPath;        public SampleView(Context context) {            super(context);            setFocusable(true);                        mPaint = new Paint();            mPaint.setAntiAlias(true);            mPaint.setStrokeWidth(6);            mPaint.setTextSize(16);            mPaint.setTextAlign(Paint.Align.RIGHT);                        mPath = new Path();        }                private void drawScene(Canvas canvas) {            canvas.clipRect(0, 0, 100, 100);                        canvas.drawColor(Color.WHITE);                        mPaint.setColor(Color.RED);            canvas.drawLine(0, 0, 100, 100, mPaint);                        mPaint.setColor(Color.GREEN);            canvas.drawCircle(30, 70, 30, mPaint);                        mPaint.setColor(Color.BLUE);            canvas.drawText("Clipping", 100, 30, mPaint);        }                @Override         protected void onDraw(Canvas canvas) {            canvas.drawColor(Color.GRAY);                        canvas.save();            canvas.translate(10, 10);            drawScene(canvas);            canvas.restore();                        canvas.save();            canvas.translate(160, 10);            canvas.clipRect(10, 10, 90, 90);            canvas.clipRect(30, 30, 70, 70, Region.Op.DIFFERENCE);            drawScene(canvas);            canvas.restore();                        canvas.save();            canvas.translate(10, 160);            mPath.reset();            canvas.clipPath(mPath); // makes the clip empty            mPath.addCircle(50, 50, 50, Path.Direction.CCW);            canvas.clipPath(mPath, Region.Op.REPLACE);            drawScene(canvas);            canvas.restore();                        canvas.save();            canvas.translate(160, 160);            canvas.clipRect(0, 0, 60, 60);            canvas.clipRect(40, 40, 100, 100, Region.Op.UNION);            drawScene(canvas);            canvas.restore();                        canvas.save();            canvas.translate(10, 310);            canvas.clipRect(0, 0, 60, 60);            canvas.clipRect(40, 40, 100, 100, Region.Op.XOR);            drawScene(canvas);            canvas.restore();                        canvas.save();            canvas.translate(160, 310);            canvas.clipRect(0, 0, 60, 60);            canvas.clipRect(40, 40, 100, 100, Region.Op.REVERSE_DIFFERENCE);            drawScene(canvas);            canvas.restore();        }    }}

效果如图：

canvas.clipRect(30, 30, 70, 70, Region.Op.XOR);最后一个参数有多个选择分别是：

            //DIFFERENCE是第一次不同于第二次的部分显示出来
            //REPLACE是显示第二次的
            //REVERSE_DIFFERENCE 是第二次不同于第一次的部分显示
            //INTERSECT交集显示
            //UNION全部显示
            //XOR补集就是全集的减去交集生育部分显示

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