绘制虚线

方法一

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CGFloat width = self.frame.size.width;
CGFloat height = self.frame.size.height;

CGPoint p1 = CGPointMake(15, height-15);
CGPoint p2 = CGPointMake(width - 15, height-15);
//获得处理的上下文
CGContextRef context = UIGraphicsGetCurrentContext();
//设置颜色
CGContextSetStrokeColorWithColor(context, [UIColor lightGrayColor].CGColor);
//设置线条粗细宽度
CGContextSetLineWidth(context, 1);
//起始点设置
CGContextMoveToPoint(context, p1.x, p1.y);
//设置下一个坐标点
CGContextAddLineToPoint(context, p2.x, p2.y);
//设置虚线排列的宽度间隔:下面的lengths中的数字表示先绘制3个点再绘制1个点
CGFloat lengths[] = {5,3,5};
//设置虚线 下面最后一个参数“3”代表排列的个数，即count的值等于lengths数组的长度
CGContextSetLineDash(context, 0, lengths, 3);
//连接上面定义的坐标点 设置线条样式
CGContextDrawPath(context, kCGPathStroke);

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lengths的值｛10,10｝表示先绘制10个点，再跳过10个点，如此反复，如图：

image.png

如果把lengths值改为｛10, 20, 10｝，则表示先绘制10个点，跳过20个点，绘制10个点，跳过10个点，再绘制20个点，如此反复，如图：

image.png

方法二

/**
  ** lineView:       需要绘制成虚线的view
  ** lineLength:     虚线的宽度
  ** lineSpacing:    虚线的间距 
  ** lineColor:      虚线的颜色
  **/
+ (void)drawDashLine:(UIView *)lineView lineLength:(int)lineLength lineSpacing:(int)lineSpacing lineColor:(UIColor *)lineColor
{    
      CAShapeLayer *shapeLayer = [CAShapeLayer layer];
      [shapeLayer setBounds:lineView.bounds];
      [shapeLayer setPosition:CGPointMake(CGRectGetWidth(lineView.frame) / 2, CGRectGetHeight(lineView.frame))];   
      [shapeLayer setFillColor:[UIColor clearColor].CGColor];  
      //  设置虚线颜色为blackColor    
      [shapeLayer setStrokeColor:lineColor.CGColor];   
      //  设置虚线宽度   
      [shapeLayer setLineWidth:CGRectGetHeight(lineView.frame)];    
      [shapeLayer setLineJoin:kCALineJoinRound];    
      //  设置线宽，线间距
      [shapeLayer setLineDashPattern:[NSArray arrayWithObjects:[NSNumber numberWithInt:lineLength], [NSNumber numberWithInt:lineSpacing], nil]];   
      //  设置路径    
      CGMutablePathRef path = CGPathCreateMutable();   
      CGPathMoveToPoint(path, NULL, 0, 0);  
      CGPathAddLineToPoint(path, NULL,CGRectGetWidth(lineView.frame), 0);
      [shapeLayer setPath:path];    
      CGPathRelease(path);   
      //  把绘制好的虚线添加上来   
      [lineView.layer addSublayer:shapeLayer];
  }