iOS 学习 - 11.圆角(小于等于四个)类似气泡和计算字符高度

使用贝塞尔曲线，

// 小于四个角 圆角
-(void)setbor{

    NSString *str = @" couldn't fit this all in a comment to @lomanf's answer. So I'm adding it as an answer.";
    //计算字符高度
    [Corner layoutHeightWithLable:self.label text:str];
    /*
     1.使用空白 view addSubView label
     2.得到类似 qq 聊天气泡，仅仅只是类似，还是有区别
     */
    UIView *view = [[UIView alloc]init];
    //view 的 frame 要比 label 大一点，不然切圆角会切到字符串
    view.frame = CGRectMake( ,  , _label.frame.size.width +  , _label.frame.size.height + );
    view.backgroundColor = [UIColor redColor];
    //圆角
    [Corner createCornerInView:view corners:UIRectCornerBottomLeft|UIRectCornerTopRight cgsize:CGSizeMake(, )];

    [self.view addSubview:view];
    [view addSubview:_label];
}

新建了一个类：Corner

.h

#import <UIKit/UIKit.h>

@interface Corner : UIView

+(void)createCornerInView:(UIView *)view corners:(UIRectCorner)corner cgsize:(CGSize)size;

+(void)layoutHeightWithLable:(UILabel *)label text:(NSString *)text;
@end

.m

+(void)layoutHeightWithLable:(UILabel *)label text:(NSString *)text{
    label.numberOfLines = ;
    label.lineBreakMode = NSLineBreakByWordWrapping;
    CGSize maxSize = CGSizeMake(, MAXFLOAT);
    CGSize textSize = [text boundingRectWithSize:maxSize options:(NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin) attributes:@{NSFontAttributeName:label.font} context:nil].size;
    label.frame = CGRectMake(label.frame.origin.x, label.frame.origin.y, textSize.width, textSize.height);
    label.text = text;
}

+(void)createCornerInView:(UIView *)view corners:(UIRectCorner)corner cgsize:(CGSize)size{
    /*
     typedef NS_OPTIONS(NSUInteger, UIRectCorner) {
     UIRectCornerTopLeft     = 1 << 0,  - 左上角
     UIRectCornerTopRight    = 1 << 1,  - 右上角
     UIRectCornerBottomLeft  = 1 << 2,  - 左下角
     UIRectCornerBottomRight = 1 << 3,  - 右下角
     UIRectCornerAllCorners  = ~0UL     - 四只角
     };
     */
    //贝塞尔曲线
    UIBezierPath *bezierPath = [UIBezierPath bezierPathWithRoundedRect:view.bounds byRoundingCorners:corner cornerRadii:size];
    CAShapeLayer *maskLayer = [[CAShapeLayer alloc]init];
    maskLayer.frame = view.bounds;
    maskLayer.path = bezierPath.CGPath;
    view.layer.mask = maskLayer;
}