有时候需要为UIView添加虚线描边，本文记录一种实现方式，主要是通过对UIView的根layer添加CAShapeLayer来完成。效果图如下:

CGSize screenSize = [UIScreen mainScreen].bounds.size;
CGFloat    viewWidth = 200;CGFloat viewHeight = 200;
UIView *view = [[UIView alloc] initWithFrame:CGRectMake((screenSize.width - viewWidth)/2, (screenSize.height - viewHeight) / 2, viewWidth, viewHeight)];
view.backgroundColor = [UIColor colorWithWhite:0.9 alpha:1];
view.layer.cornerRadius = CGRectGetWidth(view.bounds)/2;
CAShapeLayer *borderLayer = [CAShapeLayer layer];
borderLayer.bounds = CGRectMake(0, 0, viewWidth, viewHeight);
borderLayer.position = CGPointMake(CGRectGetMidX(view.bounds), CGRectGetMidY(view.bounds));// 
borderLayer.path = [UIBezierPath bezierPathWithRect:borderLayer.bounds].CGPath;
borderLayer.path = [UIBezierPath bezierPathWithRoundedRect:borderLayer.bounds cornerRadius:CGRectGetWidth(borderLayer.bounds)/2].CGPath;borderLayer.lineWidth = 1. / [[UIScreen mainScreen] scale];
//虚线边框borderLayer.lineDashPattern = @[@8, @8];
//实线边框// borderLayer.lineDashPattern = nil;
borderLayer.fillColor = [UIColor clearColor].CGColor;
borderLayer.strokeColor = [UIColor redColor].CGColor;
[view.layer addSublayer:borderLayer];
[self.view addSubview:view];

可通过修改UIBezierPath来改变虚线框的路径。如果想把边框绘制成实线，可将borderLayer.lineDashPattern
置为nil
即可。