1. Path概念

用Path定义一个图形，然后用canvas.drawPath(...)函数来绘制这个图形。例如绘制一个圆。Path可以绘制各种图形，如二次，三次贝塞尔曲线，圆形、多边形，三角形，五角星等几何形状。

      public class PathOpView extends View {
      private Paint mPaint;
       public PathOpView(Context context) {
      super(context);
       mPaint = new Paint();
       mPaint.setColor(Color.RED);
       mPaint.setStrokeWidth(8);
       mPaint.setStyle(Paint.Style.STROKE);
       mPaint.setAntiAlias(true);
       }
      @Override
      protected void onDraw(Canvas canvas) {
      super.onDraw(canvas);
       drawCircle(canvas)
       }
      private void drawCircle(Canvas canvas) {
      Path path = new Path();
       path.addCircle(150, 150, 100, Path.Direction.CW);
       canvas.drawPath(path,mPaint);
       }
      }
  
 

在上述代码中的drawCircle函数里，new一个Path，调用Path.addCircle定义一个圆形路径区域，最后调用canvas.drawPath绘制出这个圆形区域。

2.  两个path之间的合并

现在有以下几种合并方式：

 Path.Op.DIFFERENCE Path1调用合并函数：减去Path2后Path1区域剩下的部分
 

 Path.Op.INTERSECT 保留Path2 和 Path1 共同的部分
 

 Path.Op.UNION 保留Path1 和 Path 2
 

 Path.Op.XOR 保留Path1 和 Path2 + 共同的部分
 

 Path.Op.REVERSE_DIFFERENCE  与 Path.Op.DIFFERENCE相反，减去Path1后Path2区域剩下的部分
 

2.1  Path.Op.DIFFERENCE

绘制两个圆，使用Path.Op.DIFFERENCE模式，最终的结果是 Path1圆减去path2圆后剩下的部分

最终效果图如下：其灰色表示最初的2个圆path，红色表示经过Path.Op.DIFFERENCE模式合并后，剩下的path1部分。

源码如下：

      package com.xiaowei.path_basic;
      import android.content.Context;
      import android.graphics.Canvas;
      import android.graphics.Color;
      import android.graphics.Paint;
      import android.graphics.Path;
      import android.view.View;
      /**
       * Created by Xiaowei
       */
      public class PathOpView extends View {
      private Paint mPaint;
      public PathOpView(Context context) {
      super(context);
       mPaint = new Paint();
       mPaint.setColor(Color.RED);
       mPaint.setStrokeWidth(8);
       mPaint.setStyle(Paint.Style.STROKE);
       mPaint.setAntiAlias(true);
       }
      @Override
      protected void onDraw(Canvas canvas) {
      super.onDraw(canvas);
      // DIFFERENCE -- 减去Path2后Path1区域剩下的部分
       drawDifferenceOp(canvas);
       }
        private void drawDifferenceOp(Canvas canvas) {
       Path path1 = new Path();
       path1.addCircle(150, 150, 100, Path.Direction.CW);
       Path path2 = new Path();
       path2.addCircle(200, 200, 100, Path.Direction.CW);
       path1.op(path2, Path.Op.DIFFERENCE);
       canvas.drawPath(path1, mPaint);
       mPaint.setColor(Color.DKGRAY);
       mPaint.setStrokeWidth(2);
       canvas.drawCircle(150, 150, 100,mPaint);
       canvas.drawCircle(200, 200, 100,mPaint);
       }
      }
  
 

其中drawDifferenceOp函数里，定义了2个路径path1与path2两个圆形路径,         path1.op(path2, Path.Op.DIFFERENCE); 将2个路径合并，合并方法为：path1减去path2后，剩下的部分。后面的2个canvas.drawCircle(......)是绘制出没有合并的2个圆，用于对比合并后的图形。

2.2 Path.Op.INTERSECT 模式

保留两个圆相交的区域

效果图如下：

核心代码如下：

      private void drawIntersectOp(Canvas canvas) {
       Path path1 = new Path();
       path1.addCircle(150, 150, 100, Path.Direction.CW);
       Path path2 = new Path();
       path2.addCircle(200, 200, 100, Path.Direction.CW);
       path1.op(path2, Path.Op.INTERSECT);
       canvas.drawPath(path1, mPaint);
       mPaint.setColor(Color.DKGRAY);
       mPaint.setStrokeWidth(2);
       canvas.drawCircle(150, 150, 100,mPaint);
       canvas.drawCircle(200, 200, 100,mPaint);
       }
  
 

上述drawIntersectOp函数也是在onDraw里调用，下文中的核心函数也是同样。

2.3 Path.Op.UNION

合并path1和path2

效果图：

核心代码：

      private void drawUnionOp(Canvas canvas) {
       Path path1 = new Path();
       path1.addCircle(150, 150, 100, Path.Direction.CW);
       Path path2 = new Path();
       path2.addCircle(200, 200, 100, Path.Direction.CW);
       path1.op(path2, Path.Op.UNION);
       canvas.drawPath(path1, mPaint);
       mPaint.setColor(Color.DKGRAY);
       mPaint.setStrokeWidth(2);
       canvas.drawCircle(150, 150, 100,mPaint);
       canvas.drawCircle(200, 200, 100,mPaint);
       }
  
 

2.4 Path.Op.XOR

path1+path2+两者的共同部分

效果图如下：

核心代码：

      private void drawXorOp(Canvas canvas) {
       Path path1 = new Path();
       path1.addCircle(150, 150, 100, Path.Direction.CW);
       Path path2 = new Path();
       path2.addCircle(200, 200, 100, Path.Direction.CW);
       path1.op(path2, Path.Op.XOR);
       canvas.drawPath(path1, mPaint);
       mPaint.setColor(Color.DKGRAY);
       mPaint.setStrokeWidth(2);
       canvas.drawCircle(150, 150, 100,mPaint);
       canvas.drawCircle(200, 200, 100,mPaint);
       }
  
 

2.5  Path.Op.REVERSE_DIFFERENCE

与DIFFERENCE相反，保留的是path2 - path1后剩下的 path2部分

效果图如下：

核心代码：

      private void drawReverseDifferenceOp(Canvas canvas) {
       Path path1 = new Path();
       path1.addCircle(150, 150, 100, Path.Direction.CW);
       Path path2 = new Path();
       path2.addCircle(200, 200, 100, Path.Direction.CW);
       path1.op(path2, Path.Op.REVERSE_DIFFERENCE);
       canvas.drawPath(path1, mPaint);
       mPaint.setColor(Color.DKGRAY);
       mPaint.setStrokeWidth(2);
       canvas.drawCircle(150, 150, 100,mPaint);
       canvas.drawCircle(200, 200, 100,mPaint);
       }
  
 

demo源码：https://download.csdn.net/download/gaoxiaoweiandy/12435514

文章来源: blog.csdn.net，作者：冉航--小虾米，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/gaoxiaoweiandy/article/details/106194583