将省略号添加到NSString

Question

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那样剪切文本。 换句话说，我必须弄清楚我自己的省略号（'...'）。

 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:@"..."];
        }

我很难找到基于CGSize的'...'的范围。 解决这个问题的最佳方法是什么？

这是我绘制它的方式：

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);

Answer 1

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。我删除了它，因为它导致比它解决的更多混乱。答案是正确的代码。）

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

- (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);
}

Answer 2

这样的事情怎么样......

- (NSString *)truncate:(NSString *)string toWidth:(CGFloat)width withFont:(UIFont *)font {

    CGSize size = [string sizeWithFont:font];
    if (size.width <= width) return string;

    NSString *truncatedString = [string copy];
    NSString *ellipticalString = [truncatedString stringByAppendingString:@"..."];
    size = [ellipticalString sizeWithFont:font];

    while (size.width > width && truncatedString.length) {
        truncatedString = [truncatedString substringToIndex:(truncatedString.length-1)];
        ellipticalString = [truncatedString stringByAppendingString:@"..."];
        size = [ellipticalString sizeWithFont:font];
    }
    return ellipticalString;
}

Answer 3

最简单最方便的方式，

NSString *theText = @"bla blah bla bhla bla bla";
NSMutableParagraphStyle *style = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
[style setLineBreakMode:NSLineBreakByTruncatingTail];
[theText drawInRect:dirtyRect withAttributes:[NSDictionary dictionaryWithObjectsAndKeys:style, NSParagraphStyleAttributeName,nil]];

更多