[转]Android Canvas 切割 clipRect

最新推荐文章于 2024-05-04 23:57:40 发布

转载最新推荐文章于 2024-05-04 23:57:40 发布 · 61 阅读

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原文链接：http://www.cnblogs.com/GnagWang/archive/2011/06/28/2092313.html

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#移动开发

本文详细解析了Android中使用Canvas.clipRect方法进行画布裁剪的过程，包括参数选择和实际应用案例。

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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

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);
    }
}