iOS 設置按鈕圓角(4個角都可隨意設置)

https://yq.aliyun.com/ziliao/4779

設置按鈕的4個角：
左上：UIRectCornerTopLeft
左下：UIRectCornerBottomLeft
右上：UIRectCornerTopRight
右下：UIRectCornerBottomRight

例子代碼：

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(50, 60, 80, 40)];
button.backgroundColor = [UIColor orangeColor];
[self.view addSubview:button];
 
//這里設置的是左上和左下角
UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:button.bounds   byRoundingCorners:UIRectCornerBottomLeft |    UIRectCornerTopLeft    cornerRadii:CGSizeMake(8, 8)];
CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
maskLayer.frame = button.bounds;
maskLayer.path = maskPath.CGPath;
button.layer.mask = maskLayer;

效果圖：