将省略号添加到NSString [英] adding ellipsis to NSString

问题描述

我有以下代码，我试图使用核心文本绘制，这就是为什么我不能像UILabel那样剪辑文本。换句话说，我必须弄清楚自己的省略号（'...'）。

I have the following code, which I am trying to draw using core text and that's why I can't clip the text like what UILabel does. in other words I have to figure out the ellipsis ('...') my self.

 CGSize commentSize = [[self.sizeDictionary_ valueForKey:commentSizeKey] CGSizeValue];
        CGSize actualSize = [[self.sizeDictionary_ valueForKey:actualCommentSizeKey] CGSizeValue];

 NSString *actualComment = self.highlightItem_.comment;
        if (actualSize.height > commentSize.height){
            actualComment = [self.highlightItem_.comment stringByReplacingCharactersInRange:NSMakeRange(68, 3) withString:@"..."];
        }

我很难找到'...的范围'基于CGSize。想出这个问题的最佳方法是什么？

I am having a difficult time finding the range of where the '...' based on a CGSize. What would be the best way in figuring this out?

以下是我如何绘制它：

CFStringRef string = CFBridgingRetain(actualComment);
        CFMutableAttributedStringRef comment = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
        CFAttributedStringReplaceString (comment ,CFRangeMake(0, 0), string);

        CGColorRef blue = CGColorRetain([UIColor colorWithRed:131/255.f green:204/255.f blue:253/255.f alpha:1.0].CGColor);
        CGColorRef gray = CGColorRetain([UIColor colorWithWhite:165/255.f alpha:1.0].CGColor);

        CFAttributedStringSetAttribute(comment, CFRangeMake(0, [name length]),kCTForegroundColorAttributeName, blue);
        CFAttributedStringSetAttribute(comment, CFRangeMake([name length],  [self.highlightItem_.comment length] - [name length]),kCTForegroundColorAttributeName, gray);

        CGColorRelease (blue);
        CGColorRelease (gray);

        CTFontRef nameFont = CTFontCreateWithName(CFBridgingRetain(kProximaNovaBold), 13.0f, nil);
        CFAttributedStringSetAttribute(comment,CFRangeMake(0, [name length]),kCTFontAttributeName,nameFont);

        CTFontRef commentFont = CTFontCreateWithName(CFBridgingRetain(kProximaNovaRegular), 13.0f, nil);
        CFAttributedStringSetAttribute(comment, CFRangeMake([name length],  [self.highlightItem_.comment length] - [name length]),kCTFontAttributeName,commentFont);

        CGFloat commentYOffset = floorf((self.commentHeight_ - commentSize.height)/2);

        CGContextSaveGState(context);
        CGRect captionFrame = CGRectMake(0, 0, rect.size.width - 80, commentSize.height);
        CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(comment);
        CGMutablePathRef captionFramePath = CGPathCreateMutable();
        CGPathAddRect(captionFramePath, NULL, captionFrame);

        CTFrameRef mainCaptionFrame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), captionFramePath, NULL);

        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSetTextMatrix(context, CGAffineTransformIdentity);
        CGContextTranslateCTM(context, self.buttonSize_ + 25, self.imageHeight_ + self.commentHeight_ + 6 - commentYOffset);
        CGContextScaleCTM(context, 1.0, -1.0);

        CTFrameDraw(mainCaptionFrame, context);
        CGContextRestoreGState(context);

推荐答案

编辑

（我在这里的原始答案没有用;它没有处理多行。如果有人想看到它的历史兴趣，请查看编辑历史记录。我已删除它，因为它导致比你解决的更混乱。目前的答案是正确的代码。）

你需要做的是让 CTFramesetter 计算除最后一行之外的所有行。然后，如果需要，你可以手动截断最后一个。

What you need to do is let CTFramesetter work out all the lines except the last one. Then you can truncate the last one by hand if required.

- (void)drawRect:(CGRect)rect
{
  CGContextRef context = UIGraphicsGetCurrentContext();
  CGContextSetTextMatrix(context, CGAffineTransformIdentity);

  CGRect pathRect = CGRectMake(50, 200, 200, 40);
  CGPathRef path = CGPathCreateWithRect(pathRect, NULL);

  CFAttributedStringRef attrString = (__bridge CFTypeRef)[self attributedString];

  // Create the framesetter using the attributed string
  CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attrString);

  // Create a single frame using the entire string (CFRange(0,0))
  // that fits inside of path.
  CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);

  // Draw the lines except the last one
  CFArrayRef lines = CTFrameGetLines(frame);
  CFIndex lineCount = CFArrayGetCount(lines);
  CGPoint origins[lineCount]; // I'm assuming that a stack variable is safe here.
                              // This would be bad if there were thousdands of lines, but that's unlikely.
  CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), origins);
  for (CFIndex i = 0; i < lineCount - 1; ++i) {
    CGContextSetTextPosition(context, pathRect.origin.x + origins[i].x, pathRect.origin.y + origins[i].y);
    CTLineDraw(CFArrayGetValueAtIndex(lines, i), context);
  }

  ///
  /// HERE'S THE INTERESTING PART
  ///
  // Make a new last line that includes the rest of the string.
  // The last line is already truncated (just with no truncation mark), so we can't truncate it again
  CTLineRef lastLine = CFArrayGetValueAtIndex(lines, lineCount - 1);
  CFIndex lastLocation = CTLineGetStringRange(lastLine).location;
  CFRange restRange = CFRangeMake(lastLocation, CFAttributedStringGetLength(attrString) - lastLocation);
  CFAttributedStringRef restOfString = CFAttributedStringCreateWithSubstring(NULL, attrString, restRange);
  CTLineRef restLine = CTLineCreateWithAttributedString(restOfString);


  // We need to provide the truncation mark. This is an ellipsis (Cmd-semicolon).
  // You could also use "\u2026". Don't use dot-dot-dot. It'll work, it's just not correct.
  // Obviously you could cache this…
  CTLineRef ellipsis = CTLineCreateWithAttributedString((__bridge CFTypeRef)
                                                        [[NSAttributedString alloc] initWithString:@"…"]);

  // OK, now let's truncate it and draw it. I'm being a little sloppy here. If ellipsis could possibly
  // be wider than the path width, then this will fail and truncateLine will be NULL and we'll crash.
  // Don't do that.
  CTLineRef truncatedLine = CTLineCreateTruncatedLine(restLine,
                                                      CGRectGetWidth(pathRect),
                                                      kCTLineTruncationEnd,
                                                      ellipsis);
  CGContextSetTextPosition(context, pathRect.origin.x + origins[lineCount - 1].x, pathRect.origin.y + origins[lineCount - 1].y);
  CTLineDraw(truncatedLine, context);

  CFRelease(truncatedLine);
  CFRelease(ellipsis);
  CFRelease(restLine);
  CFRelease(restOfString);
  CFRelease(frame);
  CFRelease(framesetter);
  CGPathRelease(path);
}

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