boundingRectWithSize 的使用

- (CGRect)boundingRectWithSize:(CGSize)size options:(NSStringDrawingOptions)options context:(NSStringDrawingContext *)context NS_AVAILABLE_IOS(6_0);

使用時的注意事項:

1: NSAttributedString 的每一個部分都要至少設置兩個屬性: 

NSFontAttributeName

NSForegroundColorAttributeName

 

2: NSStringDrawingOptions 的值, 在多行的狀況下, 至少要有   

NSStringDrawingUsesLineFragmentOrigin

NSStringDrawingUsesFontLeading

 

3: 若是文字中可能會出現emoji表情的話, emoji的高度比文字要高一點點, 

個人方即是簡單的在高度基礎上加了兩個像素.  

(用CoreText可能會好一些, 但相對複雜.)

4.

labels.numberOfLines = 0;      行數可變

附代碼:

 

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;  // 加兩個像素,防止emoji被切掉.