03-副文本属性

 

-UITextField占位文字相关的设置

// 设置占位文字内容

@property(nullable, nonatomic,copy)   NSString  *placeholder;

// 设置带有属性的占位文字, 优先级 > placeholder

@property(nullable, nonatomic,copy)   NSAttributedString     *attributedPlaceholder;

 

## NSAttributedString
- 带有属性的字符串, 富文本
- 由2部分组成
    - 文字内容 : NSString *
    - 文字属性 : NSDictionary *
        - 文字颜色 - NSForegroundColorAttributeName
        - 字体大小 - NSFontAttributeName
        - 下划线 - NSUnderlineStyleAttributeName
        - 背景色 - NSBackgroundColorAttributeName
- 初始化

 

NSMutableDictionary *attributes = [NSMutableDictionary dictionary];

attributes[NSForegroundColorAttributeName] = [UIColor yellowColor];
attributes[NSBackgroundColorAttributeName] = [UIColor redColor];
attributes[NSUnderlineStyleAttributeName] = @YES;
NSAttributedString *string = [[NSAttributedString alloc] initWithString:@"123" attributes:attributes];
```
- 使用场合
    - UILabel - attributedText
    - UITextField - attributedPlaceholder

## NSMutableAttributedString
- 继承自NSAttributedString
- 常见方法

// 设置range范围的属性, 重复设置同一个范围的属性, 最后一次设置才是有效的(之前的设置会被覆盖掉)
- (void)setAttributes:(nullable NSDictionary<NSString *, id> *)attrs range:(NSRange)range;
// 添加range范围的属性, 同一个范围, 可以不断累加属性
- (void)addAttribute:(NSString *)name value:(id)value range:(NSRange)range;

- (void)addAttributes:(NSDictionary<NSString *, id> *)attrs range:(NSRange)range;

 

---

 

- 图文混排

UILabel *label = [[UILabel alloc] init];
label.frame = CGRectMake(100, 100, 200, 25);
label.backgroundColor = [UIColor redColor];
label.font = [UIFont systemFontOfSize:14];
[self.view addSubview:label];

// 图文混排
NSMutableAttributedString *attributedText = [[NSMutableAttributedString alloc] init];
// 1 - 你好
NSAttributedString *first = [[NSAttributedString alloc] initWithString:@"你好"];
[attributedText appendAttributedString:first];

// 2 - 图片
// 带有图片的附件对象
NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
attachment.image = [UIImage imageNamed:@"header_cry_icon"];
CGFloat lineH = label.font.lineHeight;
attachment.bounds = CGRectMake(0, - ((label.xmg_height - lineH) * 0.5 - 1), lineH, lineH);
// 将附件对象包装成一个属性文字
NSAttributedString *second = [NSAttributedString attributedStringWithAttachment:attachment];
[attributedText appendAttributedString:second];

// 3 - 哈哈哈
NSAttributedString *third = [[NSAttributedString alloc] initWithString:@"哈哈哈"];
[attributedText appendAttributedString:third];

label.attributedText = attributedText;

 

---

 

- 一个Label显示多行不同字体的文字

 

UILabel *label = [[UILabel alloc] init];

// 设置属性文字
NSString *text = @"你好\n哈哈哈";
NSMutableAttributedString *attributedText = [[NSMutableAttributedString alloc] initWithString:text];
[attributedText addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:10] range:NSMakeRange(0, text.length)];
[attributedText addAttribute:NSFontAttributeName value:[UIFont boldSystemFontOfSize:13] range:NSMakeRange(3, 3)];
label.attributedText = attributedText;
// 其他设置
label.numberOfLines = 0;
label.textAlignment = NSTextAlignmentCenter;
label.frame = CGRectMake(0, 0, 100, 40);
[self.view addSubview:label];

self.navigationItem.titleView = label;