iOS指定任意角的圆角

借助CAShapeLayer可以实现指定视图任意角的圆角，步骤如下

• 设置视图的宿主图层为CAShapeLayer

+(Class)layerClass {
    
    return [CAShapeLayer class];
}

• 构造圆角图像的Path

    CornerButton *button = [[CornerButton alloc] init];
    [button setTitle:@"hello" forState:UIControlStateNormal];
    [button setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    button.frame = CGRectMake(50, 50, 100, 30);
    CAShapeLayer *layer = (CAShapeLayer *)button.layer;
    CGRect rect = button.bounds;
    CGSize raddii = CGSizeMake(20, 20);
    UIRectCorner corners = UIRectCornerTopLeft|UIRectCornerTopRight;
    UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:corners cornerRadii:raddii];
    layer.path = path.CGPath;

视图默认的宿主图层为CALayer，CAShapeLayer继承与CALayer,设置宿主图层为CAShapeLayer不会影响源视图的绘制等效果。