没设置之前的效果
// 单边圆角或者单边框
UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:_testLab.bounds byRoundingCorners:(UIRectCornerTopLeft | UIRectCornerBottomRight) cornerRadii:CGSizeMake(5,5)];
//圆角大小 CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
maskLayer.frame = _testLab.bounds;
maskLayer.path = maskPath.CGPath;
_testLab.layer.mask = maskLayer;
