从UILabel获取截断的文本 [英] Get truncated text from UILabel

问题描述

无论如何我可以获得UILabel文本的截断版本吗？

Is there anyway I can get the truncated version of the text for a UILabel?

简而言之，我有一段文字和两个 UILabels - 标签A，长2行，标签B，高度可变。标签A在标签B上方。想法是标签A显示文本段落的前两行，并且在某个用户操作时，标记B因为可见并显示文本的其余部分。

In short, I have a paragraph of text, and two UILabels - label A, which is 2 lines long, and label B, which is a variable height. Label A is above label B. The idea is that label A shows the first two lines of the paragraph of text, and upon a certain user action, label B because visible and displays the rest of the text.

我无法确定标签B中的内容，因为我不知道标签A中显示的是什么。我还需要从标签A中删除... 。

I'm having trouble determining what should go in label B, as I don't know what's being shown in label A. I'd need to also remove the "..." from label A.

注意：我意识到这有点令人费解，但有一些很好的理由，我不会把这个问题弄得一团糟。

Note: I realize this is a bit convoluted but there are some good reasons for it, which I won't clutter up the question with.

推荐答案

我想知道你是否可以使用 NSString UIKit Additions ，以确定标签A的适合程度。

I wonder if you could use the methods in the NSString UIKit Additions to figure out how much fits into label A.

粗略的方法可能是从文本的第一个字符开始并测试它将占用的大小（ -sizeWithFont：forWidth：lineBreakMod e：也许？）然后继续添加一个字符，直到它不再适合你的标签A.

A crude way might be to start with the first character of your text and test for the size it would take up (-sizeWithFont:forWidth:lineBreakMode: maybe?) and then keep adding characters one at a time until it doesn't fit into your label A any more.

I希望其他人可以提出更好的方法来做到这一点，但上述情况应该有效。

I hope somebody else can come up with a better way to do this, but the above should work.

更新

昨晚我看了一下我自己的应用程序的Core Text，并遇到了 CTFramesetterSuggestFrameSizeWithConstraints 。您可以使用此功能通过查看该函数中的 fitRange 来确定您的字符串中有多少符合标签。

Last night I looked a bit into Core Text for my own app and came across CTFramesetterSuggestFrameSizeWithConstraints. You could maybe use this to figure out how much of your string fits into the label, by looking at the fitRange in that function.

更新2：

我认为这应该可行，但我刚刚在这里输入了这个，所以它甚至可能都没有编译：

I think this should work, but I have just typed this in here, so it may not even compile:

UIFont *uiFont = [UIFont systemFontOfZise:13.0f]; // whichever font you're using
CTFontRef ctFont = CTFontCreateWithName((CFStringRef)uiFont.fontName, uiFont.pointSize, NULL);
NSDictionary *attr = [NSDictionary dictionaryWithObject:(id)ctFont forKey:(id)kCTFontAttributeName];
CFRelease(ctfont);
NSAttributedString *attrString  = [[NSAttributedString alloc] initWithString:yourLabelText attributes:attr];
CTFrameSetterRef frameSetter = CTFrameSetterCreateWithAttributedString((CFAttributedStringRef)attrString);
[attrString release];
CFRange fitRange;
CTFrameSetterSuggestFrameSizeWithConstrains(
    frameSetter,
    CFRangeMake(0, 0),
    NULL,
    CGSizeMake(labelWidth, labelHeight),
    &fitRange);
CFRelease(frameSetter);
CFIndex numberOfCharactersThatFit = fitRange.length;

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