android画图--切割区域

android切割画布的历程不算很难，可是理解起来也比较麻烦，这里写一下我的理解 但是不一定正确：
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
首先还是继承一个view，在 构造函数里面初始化一个画笔 笔宽为6 文本大小16 文本对齐方式 居右。
mPaint = new Paint();
            mPaint.setAntiAlias(true);
            mPaint.setStrokeWidth(6);
            mPaint.setTextSize(16);
            mPaint.setTextAlign(Paint.Align.RIGHT);
           
            mPath = new Path();

而在接口onDraw中 画了好几个图，每个图都进行了裁剪
@Override protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.GRAY);           
// 用来在一个独有的栈中保存数据
            canvas.save();
            canvas.translate(10, 10);
            drawScene(canvas);
// 用来清空栈中所有的数据
            canvas.restore();
           
            canvas.save();
            canvas.translate(160, 10);
            canvas.clipRect(10, 10, 90, 90);
              canvas.clipRect(30, 30, 70, 70, Region.Op.XOR);
            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();
        }
// 建立了一个方法，用于显示所画出的效果
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);
        }