根据文档,CTFramesetterSuggestFrameSizeWithConstraints()“确定字符串范围所需的帧大小”.
不幸的是,这个函数返回的大小永远不准确.这是我在做的事情：
NSAttributedString *string = [[[NSAttributedString alloc] initWithString:@"lorem ipsum" attributes:nil] autorelease];
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef) string);
CGSize textSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter,CFRangeMake(0,0),NULL,CGSizeMake(rect.size.width,CGFLOAT_MAX),NULL);
返回的大小始终具有正确的宽度计算,但高度始终略短于预期.
有没有其他方法来布局核心文本？
似乎我不是唯一遇到此方法问题的人.见https://devforums.apple.com/message/181450.
编辑：
我使用sizeWithFont：使用Quartz测量相同的字符串,为属性字符串和Quartz提供相同的字体.以下是我收到的测量数据：
Core Text: 133.569336 x 16.592285
Quartz: 135.000000 x 31.000000
解决方法
试试这..似乎工作：
+(CGFloat)heightForAttributedString:(NSAttributedString *)attrString forWidth:(CGFloat)inWidth
{
CGFloat H = 0;
// Create the framesetter with the attributed string.
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString( (CFMutableAttributedStringRef) attrString);
CGRect Box = CGRectMake(0,inWidth,CGFLOAT_MAX);
CFIndex startIndex = 0;
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path,Box);
// Create a frame for this column and draw it.
CTFrameRef frame = CTFramesetterCreateFrame(framesetter,CFRangeMake(startIndex,path,NULL);
// Start the next frame at the first character not visible in this frame.
//CFRange frameRange = CTFrameGetVisibleStringRange(frame);
//startIndex += frameRange.length;
CFArrayRef lineArray = CTFrameGetLines(frame);
CFIndex j = 0,lineCount = CFArrayGetCount(lineArray);
CGFloat h,ascent,descent,leading;
for (j=0; j < lineCount; j++)
{
CTLineRef currentLine = (CTLineRef)CFArrayGetValueAtIndex(lineArray,j);
CTLineGetTypographicBounds(currentLine,&ascent,&descent,&leading);
h = ascent + descent + leading;
NSLog(@"%f",h);
H+=h;
}
CFRelease(frame);
CFRelease(path);
CFRelease(framesetter);
return H;
}
