通过imageView来画虚线

- (void)viewDidLoad {

[super viewDidLoad];

[self getWeekDay];

_lineImg = [[UIImageView alloc] initWithFrame:CGRectMake(0, 20, self.view.bounds.size.width, 20)];

// 调用方法 返回的iamge就是虚线

_lineImg.image = [self drawLineByImageView:_lineImg];

// 添加到控制器的view上

[self.view addSubview:_lineImg];

_lineImg.backgroundColor = [UIColor whiteColor];

self.view.backgroundColor = [UIColor grayColor];

}

// 返回虚线image的方法

- (UIImage *)drawLineByImageView:(UIImageView *)imageView{

UIGraphicsBeginImageContext(imageView.frame.size); //开始画线 划线的frame

[imageView.image drawInRect:CGRectMake(0, 0, imageView.frame.size.width, imageView.frame.size.height)];

//设置线条终点形状

CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);

// 5是每个虚线的长度 4是两个虚线之间的间隔距离

CGFloat length[] = {5,4};

//    或者

//    CGFloat length[] = {3 10,20,15}; //3和20是虚线的长度，10和15 是间距的长度，

CGContextRef line = UIGraphicsGetCurrentContext();

// 设置颜色

CGContextSetStrokeColorWithColor(line, [UIColor redColor].CGColor);

CGContextSetLineDash(line, 0, length, 2); //画虚线 2是length数组的元素个数

CGContextMoveToPoint(line, 0.0, 10.0); //开始画线

CGContextAddLineToPoint(line, kScreenWidth , 10.0);

CGContextStrokePath(line);

// UIGraphicsGetImageFromCurrentImageContext()返回的就是image

return UIGraphicsGetImageFromCurrentImageContext();

}