ios - 垂直顶部对齐 UILabel 中的文本部分

Question

我们如何对标签进行子类化，使其显示文本如下前缀(顶部对齐)、文本和后缀(底部对齐)。

我目前在 UILabel 的子类上使用了以下方法

-(void)setText:(id)text withPrefixText:(id)prefixText andSuffixText:(id)suffixText {

    NSString * compondText = [self textByCompoundingText:text withPrefixText:prefixText WithsuffixText:suffixText];
    NSMutableAttributedString * attributedCompoundText = [[NSMutableAttributedString alloc] initWithString:compondText];

    NSMutableDictionary * prefixTextAttributes = [@{} mutableCopy];
    prefixTextAttributes[NSFontAttributeName]  = _prefixTextFont? _prefixTextFont:self.font;
    prefixTextAttributes[NSForegroundColorAttributeName] = _prefixTextColour? _prefixTextColour:self.textColor;
    prefixTextAttributes[(NSString*)kCTSuperscriptAttributeName] = [NSNumber numberWithUnsignedInteger:_prefixTextVerticalPositionning];

    NSMutableDictionary * suffixTextAttributes = [@{} mutableCopy];
    suffixTextAttributes[NSFontAttributeName]  = _suffixTextFont? _suffixTextFont:self.font;
    suffixTextAttributes[NSForegroundColorAttributeName] = _suffixTextColour ?_suffixTextColour:self.textColor;
    suffixTextAttributes[(NSString*)kCTSuperscriptAttributeName] = [NSNumber numberWithUnsignedInteger:_suffixTextVerticalPostioning];

    if(prefixText)
        [attributedCompoundText addAttributes:prefixTextAttributes  range:[compondText rangeOfString:prefixText]];
    if(suffixText)
        [attributedCompoundText addAttributes:suffixTextAttributes  range:[compondText rangeOfString:suffixText]];

    self.attributedText = attributedCompoundText;
}

但这将文本设置为上标并不能解决问题。前缀文本和正文的顶部应相同，但前缀文本应垂直顶部对齐且字体较小!

Answer 1

使用 NSBaselineOffsetAttributeName 解决了我的问题，使用它我们可以指定距底部的偏移量。+ve 用于上标，-ve 用于下标

   -(void)setText:(id)text withPrefixText:(id)prefixText andSuffixText:(id)suffixText
    {
     NSString * compondText = [self textByCompoundingText:text withPrefixText:prefixText      WithsuffixText:suffixText];
NSMutableAttributedString * attributedCompoundText = [[NSMutableAttributedString alloc] initWithString:compondText];

NSMutableDictionary * prefixTextAttributes = [@{} mutableCopy];
prefixTextAttributes[NSFontAttributeName]  = _prefixTextFont? _prefixTextFont:self.font;
prefixTextAttributes[NSForegroundColorAttributeName] = _prefixTextColour? _prefixTextColour:self.textColor;
NSNumber *baselineOffSet =[NSNumber numberWithUnsignedInteger:_prefixTextVerticalPositionning];
prefixTextAttributes[(NSString*)NSBaselineOffsetAttributeName] = baselineOffSet;

NSMutableDictionary * suffixTextAttributes = [@{} mutableCopy];
suffixTextAttributes[NSFontAttributeName]  = _suffixTextFont? _suffixTextFont:self.font;
suffixTextAttributes[NSForegroundColorAttributeName] = _suffixTextColour ?_suffixTextColour:self.textColor;
baselineOffSet = [NSNumber numberWithUnsignedInteger:_suffixTextVerticalPostioning];
suffixTextAttributes[(NSString*)NSBaselineOffsetAttributeName] = baselineOffSet;

if(prefixText)
    [attributedCompoundText addAttributes:prefixTextAttributes  range:[compondText rangeOfString:prefixText]];
if(suffixText)
    [attributedCompoundText addAttributes:suffixTextAttributes  range:[compondText rangeOfString:suffixText]];

self.attributedText = attributedCompoundText;

}