如何截断 UITextView 内容以适应缩小的尺寸？

Question

我真的很难理解这个问题。

正如标题所示，我在 iPhone 应用程序的视图上有多个 UITextView。我以编程方式创建它们并成功地用文本填充该文本视图，但在某些情况下，我放入视图中的文本占用的空间比我为其分配的框架更多。在这种情况下，我希望截断文本，但我不知道该怎么做。

我已经预定义了以下常量；

#define viewOriginX  20
#define viewOriginY 180

这是我的 UITextView 创建代码；

textViewOne = [[UITextView alloc] initWithFrame:CGRectMake(viewOriginX, viewOriginY + 65, 280, 45];
textViewOne.delegate = self;
textViewOne.scrollEnabled = NO;
textViewOne.contentInset = UIEdgeInsetsZero;
textViewOne.font = viewFont;
textViewOne.textColor = [UIColor blackColor];
textViewOne.textAlignment = UITextAlignmentLeft;
[self.view addSubview:textViewOne];

在某些情况下，我这里有 15 到 20 行文本，我想将其截断为 2 行。

谁能帮助我朝正确的方向前进？

提前致谢！ ：D

Answer 1

原始答案（iOS 6及更低版本）

遗憾的是，如果您需要可编辑视图，则带有numberOfLines的UILabel不会这样做。或者您想要 UITextView 的（原生）垂直对齐方式。

下面是一个 NSString 类别，它根据矩形中的大小从字符串中删除单词：

@interface NSString (StringThatFits)
- (NSString *)stringByDeletingWordsFromStringToFit:(CGRect)rect
                                         withInset:(CGFloat)inset
                                         usingFont:(UIFont *)font
@end

@implementation NSString (StringThatFits)
- (NSString *)stringByDeletingWordsFromStringToFit:(CGRect)rect
                                         withInset:(CGFloat)inset
                                         usingFont:(UIFont *)font
{
    NSString *result = [self copy];
    CGSize maxSize = CGSizeMake(rect.size.width  - (inset * 2), FLT_MAX);
    CGSize size = [result sizeWithFont:font
                           constrainedToSize:maxSize
                               lineBreakMode:UILineBreakModeWordWrap];
    NSRange range;

    if (rect.size.height < size.height)
        while (rect.size.height < size.height) {

            range = [result rangeOfString:@" "
                                        options:NSBackwardsSearch];

            if (range.location != NSNotFound && range.location > 0 ) {
                result = [result substringToIndex:range.location];
            } else {
                result = [result substringToIndex:result.length - 1];
            }

            size = [result sizeWithFont:font
                            constrainedToSize:maxSize
                                lineBreakMode:UILineBreakModeWordWrap];
        }

    return result;
}
@end

对于 UITextView，使用 8 的插入来说明 UIKit 绘制它们的方式：

CGRect rect = aTextView.frame;
NSString *truncatedString = [theString stringByDeletingWordsFromStringToFit:rect
                                     withInset:8.f
                                     usingFont:theTextView.font];

更新的答案（iOS 7）

现在UITextView内部使用TextKit，它更容易。

不要截断实际字符串，而是将 text（或 attributedText）属性设置为整个字符串并截断容器中显示的文本量（就像我们对 UILabel 所做的那样）：

self.textView.scrollEnabled = NO;
self.textView.textContainer.maximumNumberOfLines = 0;
self.textView.textContainer.lineBreakMode = NSLineBreakByTruncatingTail;

Answer 2

您可以进行字符计数。例如，如果您有这样的 UITextField：

+--------------------+
|This is a string in |
|a text view.        |
+--------------------+

每行有 20 个字符。如果您知道该数字，则可以通过 -substringToIndex: 方法简单地截断字符串。

int maxCharacters = 40; // change it to your max
if([myString length] > maxCharacters) {
    myString = [myString substringToIndex:maxCharacters];
}

---

您还可以考虑UILabel。由于您只需要 2 行文本，UILabel 的 numberOfLines 属性可以解决您的问题。

Answer 3

由于 sizeWithFont:constrainedToSize:lineBreakMode: 在 iOS 7 中已弃用，因此我做了一些更改：

- (NSString *)stringByDeletingWordsFromStringToFit:(CGRect)rect
                                     withInset:(CGFloat)inset
                                     usingFont:(UIFont *)font
{
    NSString *result = [self copy];
    CGSize maxSize = CGSizeMake(rect.size.width  - (inset * 2), FLT_MAX);
    if (!font) font = [UIFont systemFontOfSize:[UIFont systemFontSize]];
    CGRect boundingRect = [result boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName: font, } context:nil];
    CGSize size = boundingRect.size;
    NSRange range;

    if (rect.size.height < size.height)
        while (rect.size.height < size.height) {

            range = [result rangeOfString:@" "
                                    options:NSBackwardsSearch];

            if (range.location != NSNotFound && range.location > 0 ) {
                result = [result substringToIndex:range.location];
            } else {
                result = [result substringToIndex:result.length - 1];
            }

            if (!font) font = [UIFont systemFontOfSize:[UIFont systemFontSize]];
            CGRect boundingRect = [result boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName: font, } context:nil];
            size = boundingRect.size;
        }

    return result;

}

Answer 4

这是我编写的一段代码，用于截断字符串（按单词）以适应特定的宽度和高度：

- (NSString *)stringByTruncatingString:(NSString *)string toHeight:(CGFloat)height maxWidth:(CGFloat)width withFont: (UIFont *)font {

    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineBreakMode = NSLineBreakByWordWrapping;
    NSDictionary *attrDict = [NSDictionary dictionaryWithObjectsAndKeys:font, NSFontAttributeName, paragraphStyle, NSParagraphStyleAttributeName, nil];
    NSMutableString *truncatedString = [string mutableCopy];

    if ([string sizeWithAttributes: @{NSFontAttributeName: font}].height > height) {
        // this line is optional, i wrote for better performance in case the string is too big
        if([truncatedString length] > 150) truncatedString = [[truncatedString substringToIndex:150] mutableCopy];
        // keep removing the last word until string is short enough
        while ([truncatedString boundingRectWithSize:CGSizeMake(width, CGFLOAT_MAX) options:NSStringDrawingTruncatesLastVisibleLine|NSStringDrawingUsesLineFragmentOrigin attributes:attrDict context:nil].size.height > height) {
            NSRange wordrange= [truncatedString rangeOfString: @" " options: NSBackwardsSearch];
            truncatedString = [[truncatedString substringToIndex: wordrange.location] mutableCopy];
        }
        // add elipsis to the end
        truncatedString = [NSMutableString stringWithFormat:@"%@...",truncatedString];
    }
    return truncatedString;
}

用法：

NSString *smallString = [self stringByTruncatingString:veryBigString toHeight:65 maxWidth:200 withFont:[UIFont systemFontSize:14.0f]];