速读原著-Android应用开发入门教程(剪裁效果)

    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); // 选择区域

            canvas.drawColor(Color.WHITE);
            mPaint.setColor(Color.RED); // 红色直线
            canvas.drawLine(0, 0, 100, 100, mPaint);
            mPaint.setColor(Color.GREEN); // 绿色的圆
            canvas.drawCircle(30, 70, 30, mPaint);
            mPaint.setColor(Color.BLUE); // 蓝色文本
            canvas.drawText("Clipping", 100, 30, mPaint);
        }

        @Override protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.GRAY);
            canvas.save(); // 左上部分绘制
            canvas.translate(10, 10);
            drawScene(canvas);
            canvas.restore();
            canvas.save(); // 右上部分绘制
            canvas.translate(160, 10);
            canvas.clipRect(10, 10, 90, 90);
            canvas.clipRect(30, 30, 70, 70, Region.Op.DIFFERENCE); // 中间矩形被去除
            drawScene(canvas);
            canvas.restore();
            canvas.save(); // 左中部分绘制
            canvas.translate(10, 160);
            mPath.reset();
            canvas.clipPath(mPath); // 做一个圆
            mPath.addCircle(50, 50, 50, Path.Direction.CCW);
            canvas.clipPath(mPath, Region.Op.REPLACE); // 圆外部分被去除
            drawScene(canvas);
            canvas.restore();
            canvas.save(); // 右中部分绘制
            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(); // 左下部分绘制
            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(); // 右下部分绘制
            canvas.translate(160, 310);
            canvas.clipRect(0, 0, 60, 60);
            canvas.clipRect(40, 40, 100, 100, Region.Op.REVERSE_DIFFERENCE);
            drawScene(canvas);
            canvas.restore();
        }
    }

boolean clipPath(Path path) 
boolean clipPath(Path path, Region.Op op) 
boolean clipRect(Rect rect) 
boolean clipRect(float left, float top, float right, float bottom) 
boolean clipRect(float left, float top, float right, float bottom, Region.Op op)