iphone – 向NSString添加省略号

(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(50,200,40);
  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,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,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);
}