Androidcanvas画图操作之切割画布实现方法(clipRect)

canvas.clipRect(30, 30, 70, 70, Region.Op.XOR);

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Region;
import android.util.AttributeSet;
import android.view.View;
public class sBook extends View{
  Context mContext;
  Paint mPaint;
  Path mPath;
  public sBook(Context context) {
    super(context);
    init();
  }
  public sBook(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
  }
  public sBook(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init();
  }
  private void init(){
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setStrokeWidth(6);
    mPaint.setTextSize(16);
    mPaint.setTextAlign(Paint.Align.RIGHT);
    mPath = new Path();
  }
  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.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);
    mPath.cubicTo(0, 0, 100, 0, 100, 100);
    mPath.cubicTo(100, 100, 0, 100, 0, 0);
    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();
  }
  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);
  }
}