给view设置圆角

1.设置View圆角 
userhead.layer.masksToBounds = YES; userhead.layer.cornerRadius = 6.0; userhead.layer.borderWidth = 1.0; userhead.layer.borderColor = [[UIColor whiteColor] CGColor]; userhead可以是一个UIImageView,也可以是UIView 对了，记得在framework里面导入 #import <QuartzCore/QuartzCore.h> 

2.xib下设置View圆角   
这个很简单, 只需要重写  - (void)drawRect:(CGRect)rect 方法就行了

- (void)drawRect:(CGRect)rect
{
     [super drawRect:rect];
     self.imgView.layer.cornerRadius = 20;
     self.imgView.clipsToBounds = YES;
}