如何更改 UILabel 中的截断字符？

Question

当 UILabel 的文本被截断时，默认情况下会插入 3 个点。 是否可以更改或禁用这些字符？

Answer 1

我编写了一个自定义截断类，您可以将其弹出到代码中的任何位置。只需使用下面这个方法即可。如果发生截断，它将返回 true，如果您只想使用标签默认帧宽度，则 MaxWidth 可以保留为 0。将 maxWidth 设置为小于帧宽度，以在其帧范围内缩短它。

Swift 2 （带有一些用于转换的 swift 3 注释）

用法：

Truncater.replaceElipsis(forLabel: label, withString: "???")
let didTruncate = Truncater.replaceElipsis(forLabel: label, withString: "1234", andMaximumWidth: 50) //maxWidth is not number of chars, but label width in CGFloat

class:

import UIKit

class Truncater {

    class func replaceElipsis(forLabel label:UILabel, withString replacement:String) -> Bool {
        return replaceElipsis(forLabel: label, withString: replacement, andMaximumWidth:0)
    }

    class func replaceElipsis(forLabel label:UILabel, withString replacement:String, andMaximumWidth width:CGFloat) -> Bool {

        if(label.text == nil){
            return false
        }

        let origSize = label.frame;
        var useWidth = width

        if(width <= 0){
            useWidth = origSize.width //use label width by default if width <= 0
        }

        label.sizeToFit()
        let labelSize = label.text!.sizeWithAttributes([NSFontAttributeName: label.font]) //.size(attributes: [NSFontAttributeName: label.font]) for swift 3

        if(labelSize.width > useWidth){

            let original = label.text!;
            let truncateWidth = useWidth;
            let font = label.font;
            let subLength = label.text!.characters.count

            var temp = label.text!.substringToIndex(label.text!.endIndex.advancedBy(-1)) //label.text!.substring(to: label.text!.index(label.text!.endIndex, offsetBy: -1)) for swift 3
            temp = temp.substringToIndex(temp.startIndex.advancedBy(getTruncatedStringPoint(subLength, original:original, truncatedWidth:truncateWidth, font:font, length:subLength)))
            temp = String.localizedStringWithFormat("%@%@", temp, replacement)

            var count = 0

            while temp.sizeWithAttributes([NSFontAttributeName: label.font]).width > useWidth {

                count+=1

                temp = label.text!.substringToIndex(label.text!.endIndex.advancedBy(-(1+count)))
                temp = temp.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet()) //remove this if you want to keep whitespace on the end
                temp = String.localizedStringWithFormat("%@%@", temp, replacement)
            }

            label.text = temp;
            label.frame = origSize;
            return true;
        }
        else {

            label.frame = origSize;
            return false
        }
    }

    class func getTruncatedStringPoint(splitPoint:Int, original:String, truncatedWidth:CGFloat, font:UIFont, length:Int) -> Int {

        let splitLeft = original.substringToIndex(original.startIndex.advancedBy(splitPoint))

        let subLength = length/2

        if(subLength <= 0){
            return splitPoint
        }

        let width = splitLeft.sizeWithAttributes([NSFontAttributeName: font]).width

        if(width > truncatedWidth) {
            return getTruncatedStringPoint(splitPoint - subLength, original: original, truncatedWidth: truncatedWidth, font: font, length: subLength)
        }
        else if (width < truncatedWidth) {
            return getTruncatedStringPoint(splitPoint + subLength, original: original, truncatedWidth: truncatedWidth, font: font, length: subLength)
        }
        else {
            return splitPoint
        }
    }
}

Objective C

+ (bool) replaceElipsesForLabel:(UILabel*) label With:(NSString*) replacement MaxWidth:(float) width 

class:

//=============================================Header=====================================================
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface CustomTruncater : NSObject

+ (bool) replaceElipsesForLabel:(UILabel*) label With:(NSString*) replacement MaxWidth:(float) width;

@end

//========================================================================================================

#import "CustomTruncater.h"

@implementation CustomTruncater

static NSString *original;
static float truncateWidth;
static UIFont *font;
static int subLength;

+ (bool) replaceElipsesForLabel:(UILabel*) label With:(NSString*) replacement MaxWidth:(float) width {

CGRect origSize = label.frame;

float useWidth = width;

if(width <= 0)
    useWidth = origSize.size.width; //use label width by default if width <= 0

[label sizeToFit];
CGSize labelSize = [label.text sizeWithFont:label.font];

if(labelSize.width > useWidth) {

    original = label.text;
    truncateWidth = useWidth;
    font = label.font;
    subLength = label.text.length;

    NSString *temp = [label.text substringToIndex:label.text.length-1];
    temp = [temp substringToIndex:[self getTruncatedStringPoint:subLength]];
    temp = [NSString stringWithFormat:@"%@%@", temp, replacement];

    int count = 0;

    while([temp sizeWithFont:label.font].width > useWidth){

        count++;

        temp = [label.text substringToIndex:(label.text.length-(1+count))];
        temp = [temp stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; //remove this if you want to keep whitespace on the end
        temp = [NSString stringWithFormat:@"%@%@", temp, replacement];
    }

    label.text = temp;
    label.frame = origSize;
    return true;
}
else {
    label.frame = origSize;
    return false;
}
}

+ (int) getTruncatedStringPoint:(int) splitPoint {

NSString *splitLeft = [original substringToIndex:splitPoint];
subLength /= 2;

if(subLength <= 0)
    return splitPoint;

if([splitLeft sizeWithFont:font].width > truncateWidth){
    return [self getTruncatedStringPoint:(splitPoint - subLength)];
}
else if ([splitLeft sizeWithFont:font].width < truncateWidth) {
    return [self getTruncatedStringPoint:(splitPoint + subLength)];
}
else {
    return splitPoint;
}
}

@end

Answer 2

查看 -[UILabel setLineBreakMode:] 和 UILineBreakModeCharacterWrap。 -[UILabel lineBreakMode] 的默认值为 UILineBreakModeTailTruncation，这会导致末尾出现省略号。

Answer 3

正如 Javanator 所说，你必须自己进行截断。你应该使用
UIKit 上向 NSString 类添加的 sizeWithFont:forWidth:lineBreakMode: 消息，用于获取具有特定字体的字符串的宽度。这将处理所有类型的字体。

链接

Answer 4

您还可以设置

[lbl setAdjustsFontSizeToFitWidth:YES];

，这样就不需要截断文本，您可以在标签上显示完整的文本。

Answer 5

我想提供 Fonix 之前提供的更 Swifty 版本并使用 Swift 5 语法。我还决定将这些函数编写为 UILabel 的扩展。

extension UILabel {
    func replaceEllipsis(withString replacement: String, andMaximumWidth width: CGFloat = 0) -> Bool {

        if let labelText = self.text, let font = self.font {
            let origSize = self.frame
            var useWidth = width

            if width <= 0 {
                useWidth = origSize.width // use label width by default if width <= 0
            }

            self.sizeToFit()
            let labelSize = labelText.size(withAttributes: [NSAttributedString.Key.font: font])

            if labelSize.width > useWidth {
                let truncateWidth = useWidth
                let subLength = labelText.count

                var newText = String(labelText[..<labelText.index(labelText.endIndex, offsetBy: -1)])
                newText = String(newText[..<newText.index(labelText.startIndex, offsetBy: getTruncatedStringPoint(splitPoint: subLength,
                                                                                                                  original: labelText,
                                                                                                                  truncatedWidth: truncateWidth,
                                                                                                                  font: font,
                                                                                                                  length: subLength))])
                newText = String.localizedStringWithFormat("%@%@", newText, replacement)
                var count = 0

                while newText.size(withAttributes: [NSAttributedString.Key.font: font]).width > useWidth {
                    count += 1
                    newText = String(labelText[..<labelText.index(labelText.endIndex, offsetBy: -(1 + count))])
                    newText = newText.trimmingCharacters(in: NSCharacterSet.whitespaces)
                    newText = String.localizedStringWithFormat("%@%@", newText, replacement)
                }
                self.text = newText
                self.frame = origSize
                return true
            } else {
                self.frame = origSize
                return false
            }
        } else {
            return false
        }
    }

    private func getTruncatedStringPoint(splitPoint: Int, original: String, truncatedWidth: CGFloat, font: UIFont, length: Int) -> Int {
        let index = original.index(original.startIndex, offsetBy: splitPoint)
        let splitLeft = String(original[..<index])

        let subLength = length / 2

        if subLength <= 0 {
            return splitPoint
        }

        let width = splitLeft.size(withAttributes: [NSAttributedString.Key.font: font]).width

        if width > truncatedWidth {
            return getTruncatedStringPoint(splitPoint: splitPoint - subLength, original: original, truncatedWidth: truncatedWidth, font: font, length: subLength)
        } else if width < truncatedWidth {
            return getTruncatedStringPoint(splitPoint: splitPoint + subLength, original: original, truncatedWidth: truncatedWidth, font: font, length: subLength)
        } else {
            return splitPoint
        }
    }
}

它将按如下方式使用：

<UILabel>.replaceEllipsis(withString: " ...Read More") // if you want to use the label width

如果需要，您也可以传递自定义宽度。在上面的例子中我选择了默认宽度。

有关我在重构中使用的内容的参考，以下 StackOverflow 链接很有帮助：

Advanced by refactor

substringToIndex 重构

Answer 6

为什么不编写代码来计算字符串的长度并在超出视图时生成其子字符串。或者做任何你想做的事
这是原始但有效的方法