UILabel计算文本高度

UILabel+AutoSize.mm

// 方法一：
/*
1: NSAttributedString 的每个部分都要至少设置两个属性: 

    NSFontAttributeName
    NSForegroundColorAttributeName

2: NSStringDrawingOptions 的值, 在多行的情况下, 至少要有   

    NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading

3: 如果文字中可能会出现emoji表情的话, emoji的高度比文字要高一点点, 
*/

NSMutableAttributedString *attrStr = 
        [[NSMutableAttributedString alloc] initWithString:fullDescAndTagStr];
 
NSRange allRange = [fullDescAndTagStr rangeOfString:fullDescAndTagStr];
[attrStr addAttribute:NSFontAttributeName
                value:[UIFont systemFontOfSize:13.0]
                range:allRange];
[attrStr addAttribute:NSForegroundColorAttributeName
                value:[UIColor blackColor]
                range:allRange];
 
NSRange destRange = [fullDescAndTagStr rangeOfString:tagStr];
[attrStr addAttribute:NSForegroundColorAttributeName
                value:HEXCOLOR(0x009cdd)
                range:destRange];
 
CGFloat titleHeight;
NSStringDrawingOptions options = 
        NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading;
CGRect rect = [attrStr boundingRectWithSize:CGSizeMake(labelWidth, CGFLOAT_MAX)
                                    options:options
                                    context:nil];
titleHeight = ceilf(rect.size.height);
 
return titleHeight + 2;  // 加两个像素,防止emoji被切掉.

// 方法二：
UITextView *view = [[UITextView alloc] initWithFrame:collectionView.frame];
view.text        = _postItem.content;
view.font        = [UIFont systemFontOfSize:17.0];
CGSize size      = [view sizeThatFits:CGSizeMake(CGRectGetWidth(collectionView.frame), CGFLOAT_MAX)];
view             = nil;

// 方法三：
- (CGSize)frameSizeForAttributedString:(NSAttributedString *)attributedString
{
    CTTypesetterRef typesetter = CTTypesetterCreateWithAttributedString((CFAttributedStringRef)attributedString);
    CGFloat width = YOUR_FIXED_WIDTH;

    CFIndex offset = 0, length;
    CGFloat y = 0;
    do {
        length = CTTypesetterSuggestLineBreak(typesetter, offset, width);
        CTLineRef line = CTTypesetterCreateLine(typesetter, CFRangeMake(offset, length));

        CGFloat ascent, descent, leading;
        CTLineGetTypographicBounds(line, &ascent, &descent, &leading);

        CFRelease(line);

        offset += length;
        y += ascent + descent + leading;
    } while (offset < [attributedString length]);

    CFRelease(typesetter);

    return CGSizeMake(width, ceil(y));
}