ios - 单个 UILabel 中的粗体和非粗体文本？

Question

如何在 uiLabel 中同时包含粗体和非粗体文本？

我宁愿不使用 UIWebView。我也读过这可能使用 NSAttributedString 但我不知道如何使用它。有什么想法吗？

Apple 在他们的几个应用中实现了这一点；示例截图:

谢谢!- 多姆

Answer 1

更新

在 Swift 中，我们不必处理 iOS5 旧的东西，除了语法更短，所以一切都变得非常简单:

swift 5

func attributedString(from string: String, nonBoldRange: NSRange?) -> NSAttributedString {
    let fontSize = UIFont.systemFontSize
    let attrs = [
        NSAttributedString.Key.font: UIFont.boldSystemFont(ofSize: fontSize),
        NSAttributedString.Key.foregroundColor: UIColor.black
    ]
    let nonBoldAttribute = [
        NSAttributedString.Key.font: UIFont.systemFont(ofSize: fontSize),
    ]
    let attrStr = NSMutableAttributedString(string: string, attributes: attrs)
    if let range = nonBoldRange {
        attrStr.setAttributes(nonBoldAttribute, range: range)
    }
    return attrStr
}

Swift 3

func attributedString(from string: String, nonBoldRange: NSRange?) -> NSAttributedString {
    let fontSize = UIFont.systemFontSize
    let attrs = [
        NSFontAttributeName: UIFont.boldSystemFont(ofSize: fontSize),
        NSForegroundColorAttributeName: UIColor.black
    ]
    let nonBoldAttribute = [
        NSFontAttributeName: UIFont.systemFont(ofSize: fontSize),
    ]
    let attrStr = NSMutableAttributedString(string: string, attributes: attrs)
    if let range = nonBoldRange {
        attrStr.setAttributes(nonBoldAttribute, range: range)
    }
    return attrStr
}

用法:

let targetString = "Updated 2012/10/14 21:59 PM"
let range = NSMakeRange(7, 12)

let label = UILabel(frame: CGRect(x:0, y:0, width:350, height:44))
label.backgroundColor = UIColor.white
label.attributedText = attributedString(from: targetString, nonBoldRange: range)
label.sizeToFit()

奖励:国际化

有些人评论了国际化。我个人认为这超出了这个问题的范围，但出于教学目的，我会这样做

// Date we want to show
let date = Date()

// Create the string.
// I don't set the locale because the default locale of the formatter is `NSLocale.current` so it's good for internationalisation :p
let formatter = DateFormatter()
formatter.dateStyle = .medium
formatter.timeStyle = .short
let targetString = String(format: NSLocalizedString("Update %@", comment: "Updated string format"),
                          formatter.string(from: date))

// Find the range of the non-bold part
formatter.timeStyle = .none
let nonBoldRange = targetString.range(of: formatter.string(from: date))

// Convert Range<Int> into NSRange
let nonBoldNSRange: NSRange? = nonBoldRange == nil ?
    nil :
    NSMakeRange(targetString.distance(from: targetString.startIndex, to: nonBoldRange!.lowerBound),
                targetString.distance(from: nonBoldRange!.lowerBound, to: nonBoldRange!.upperBound))

// Now just build the attributed string as before :)
label.attributedText = attributedString(from: targetString,
                                        nonBoldRange: nonBoldNSRange)

结果(假设英语和日语 Localizable.strings 可用)

---

iOS6 及更高版本的先前答案(Objective-C 仍然有效):

iOS6 UILabel, UIButton, UITextView, UITextField 支持属性字符串，这意味着我们不需要创建 CATextLayers 作为属性字符串的接收者。此外，为了制作属性字符串，我们不再需要使用 CoreText 了 :) 我们在 obj-c Foundation.framework 中有新类，例如 NSParagraphStyle 和其他常量，这将使我们的生活更轻松。耶!

所以，如果我们有这个字符串:

NSString *text = @"Updated: 2012/10/14 21:59"

我们只需要创建属性字符串:

if ([_label respondsToSelector:@selector(setAttributedText:)])
{
    // iOS6 and above : Use NSAttributedStrings
    
    // Create the attributes
    const CGFloat fontSize = 13;
    NSDictionary *attrs = @{
        NSFontAttributeName:[UIFont boldSystemFontOfSize:fontSize],
        NSForegroundColorAttributeName:[UIColor whiteColor]
    };
    NSDictionary *subAttrs = @{
        NSFontAttributeName:[UIFont systemFontOfSize:fontSize]
    };
    
    // Range of " 2012/10/14 " is (8,12). Ideally it shouldn't be hardcoded
    // This example is about attributed strings in one label
    // not about internationalisation, so we keep it simple :)
    // For internationalisation example see above code in swift
    const NSRange range = NSMakeRange(8,12);

    // Create the attributed string (text + attributes)
    NSMutableAttributedString *attributedText =
      [[NSMutableAttributedString alloc] initWithString:text
                                             attributes:attrs];
    [attributedText setAttributes:subAttrs range:range];

    // Set it in our UILabel and we are done!
    [_label setAttributedText:attributedText];
} else {
    // iOS5 and below
    // Here we have some options too. The first one is to do something
    // less fancy and show it just as plain text without attributes.
    // The second is to use CoreText and get similar results with a bit
    // more of code. Interested people please look down the old answer.

    // Now I am just being lazy so :p
    [_label setText:text];
}

有几篇很好的介绍性博客文章 here invasivecode 的人用更多示例解释了 NSAttributedString 的用法，请查找 "iOS 6 的 NSAttributedString 简介" 和 "Attributed使用 Interface Builder 的 iOS 字符串" :)

PS:上面的代码应该可以工作，但它是大脑编译的。我希望这就足够了:)

---

iOS5 及以下的旧答案

使用 CATextLayer使用 NSAttributedString !比 2 个 UILabel 更轻更简单。 (iOS 3.2 及以上)

示例。

别忘了添加 QuartzCore 框架(CALayers 需要)和 CoreText(属性字符串需要)。

#import <QuartzCore/QuartzCore.h>
#import <CoreText/CoreText.h>

下面的示例将向导航 Controller 的工具栏添加一个子层。 à la Mail.app 在 iPhone 中。 :)

- (void)setRefreshDate:(NSDate *)aDate
{
    [aDate retain];
    [refreshDate release];
    refreshDate = aDate;

    if (refreshDate) {

        /* Create the text for the text layer*/    
        NSDateFormatter *df = [[NSDateFormatter alloc] init];
        [df setDateFormat:@"MM/dd/yyyy hh:mm"];

        NSString *dateString = [df stringFromDate:refreshDate];
        NSString *prefix = NSLocalizedString(@"Updated", nil);
        NSString *text = [NSString stringWithFormat:@"%@: %@",prefix, dateString];
        [df release];

        /* Create the text layer on demand */
        if (!_textLayer) {
            _textLayer = [[CATextLayer alloc] init];
            //_textLayer.font = [UIFont boldSystemFontOfSize:13].fontName; // not needed since `string` property will be an NSAttributedString
            _textLayer.backgroundColor = [UIColor clearColor].CGColor;
            _textLayer.wrapped = NO;
            CALayer *layer = self.navigationController.toolbar.layer; //self is a view controller contained by a navigation controller
            _textLayer.frame = CGRectMake((layer.bounds.size.width-180)/2 + 10, (layer.bounds.size.height-30)/2 + 10, 180, 30);
            _textLayer.contentsScale = [[UIScreen mainScreen] scale]; // looks nice in retina displays too :)
            _textLayer.alignmentMode = kCAAlignmentCenter;
            [layer addSublayer:_textLayer];
        }

        /* Create the attributes (for the attributed string) */
        CGFloat fontSize = 13;
        UIFont *boldFont = [UIFont boldSystemFontOfSize:fontSize];
        CTFontRef ctBoldFont = CTFontCreateWithName((CFStringRef)boldFont.fontName, boldFont.pointSize, NULL);
        UIFont *font = [UIFont systemFontOfSize:13];
        CTFontRef ctFont = CTFontCreateWithName((CFStringRef)font.fontName, font.pointSize, NULL);
        CGColorRef cgColor = [UIColor whiteColor].CGColor;
        NSDictionary *attributes = [NSDictionary dictionaryWithObjectsAndKeys:
                                    (id)ctBoldFont, (id)kCTFontAttributeName,
                                    cgColor, (id)kCTForegroundColorAttributeName, nil];
        CFRelease(ctBoldFont);
        NSDictionary *subAttributes = [NSDictionary dictionaryWithObjectsAndKeys:(id)ctFont, (id)kCTFontAttributeName, nil];
        CFRelease(ctFont);

        /* Create the attributed string (text + attributes) */
        NSMutableAttributedString *attrStr = [[NSMutableAttributedString alloc] initWithString:text attributes:attributes];
        [attrStr addAttributes:subAttributes range:NSMakeRange(prefix.length, 12)]; //12 is the length of " MM/dd/yyyy/ "

        /* Set the attributes string in the text layer :) */
        _textLayer.string = attrStr;
        [attrStr release];

        _textLayer.opacity = 1.0;
    } else {
        _textLayer.opacity = 0.0;
        _textLayer.string = nil;
    }
}

在这个例子中，我只有两种不同类型的字体(粗体和普通)，但你也可以有不同的字体大小、不同的颜色、斜体、下划线等。看看NSAttributedString/NSMutableAttributedString和 CoreText attributes string keys .