Api Demo - .graphics(6)

//关键字：截取画布

package com.example.android.apis.graphics;

import android.app.Activity;
import android.content.Context;
import android.graphics.*;
import android.os.Bundle;
import android.view.View;

public class Clipping extends GraphicsActivity {

    @Override
    protected 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);//截取指定矩形为绘制区域
            
            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();//保存当前画布状态，待操作完成后restore还原。
            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);//取不同（A有B木有）
            drawScene(canvas);
            canvas.restore();
            
            canvas.save();
            canvas.translate(10, 160);
            mPath.reset();//复位路径
//            canvas.clipPath(mPath); // 清空
            mPath.addCircle(50, 50, 50, Path.Direction.CCW);//
            canvas.clipPath(mPath, Region.Op.REPLACE);//替换覆盖（B覆盖A）
            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);//取公共(A有B也有）
            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);//（只有A有或只有B有）
            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);//（B有A木有）
            drawScene(canvas);
            canvas.restore();
        }
    }
}