在UITextView的NSAttributedString上设置字体不考虑行距

我正在尝试将属性字符串设置为iOS 6中的UITextView。问题是，如果我尝试在属性字符串上设置font属性，则会忽略行距。但是，如果我未设置字体，并且使用了默认字体，则行距有效。

NSString *string = @" Hello \n world";
attrString = [[NSMutableAttributedString alloc] initWithString:string];
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle defaultParagraphStyle] mutableCopy];

paragraphStyle.minimumLineHeight = 50;
// setting the font below makes line spacing become ignored
[attrString addAttribute:NSFontAttributeName value:[UIFont boldSystemFontOfSize:20] range:NSMakeRange(0, string.length)];
[attrString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, string.length)];

mainTextView.attributedText = attrString;

知道发生了什么吗？

属性字符串编程指南：

UIFont *font = [UIFont fontWithName:@"Palatino-Roman" size:14.0];
NSDictionary *attrsDictionary = [NSDictionary dictionaryWithObject:font
                                forKey:NSFontAttributeName];
NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:@"strigil" attributes:attrsDictionary];

更新：我尝试addAttribute:在自己的应用中使用method，但在iOS 6 Simulator上似乎无法正常工作：

NSLog(@"%@", textView.attributedText);

日志似乎显示了正确添加的属性，但是iOS模拟器上的视图未显示属性。

我找到了您的问题，因为我也在与NSAttributedString进行斗争。对我来说，beginEditing和endEditing方法可以解决问题，就像更改属性字符串中所述。除此之外，lineSpacing设置setLineSpacing在段落样式上。

因此，您可能想尝试将代码更改为：

NSString *string = @" Hello \n world";
attrString = [[NSMutableAttributedString alloc] initWithString:string];
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle defaultParagraphStyle] mutableCopy];

[paragraphStyle setLineSpacing:20]  // Or whatever (positive) value you like...    
[attrSting beginEditing];

[attrString addAttribute:NSFontAttributeName value:[UIFont boldSystemFontOfSize:20] range:NSMakeRange(0, string.length)];
[attrString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, string.length)];

[attrString endEditing];

mainTextView.attributedText = attrString;

顺便说一句，虽然没有测试这个确切的代码，但是我的看起来差不多。

编辑：

同时，我已经对其进行了测试，如果我错了，请更正我，并且- beginEditingand- endEditing调用似乎非常重要。

//For proper line spacing

NSString *text1 = @"Hello";
NSString *text2 = @"\nWorld";
UIFont *text1Font = [UIFont fontWithName:@"HelveticaNeue-Medium" size:10];
NSMutableAttributedString *attributedString1 =
[[NSMutableAttributedString alloc] initWithString:text1 attributes:@{ NSFontAttributeName : text1Font }];
NSMutableParagraphStyle *paragraphStyle1 = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle1 setAlignment:NSTextAlignmentCenter];
[paragraphStyle1 setLineSpacing:4];
[attributedString1 addAttribute:NSParagraphStyleAttributeName value:paragraphStyle1 range:NSMakeRange(0, [attributedString1 length])];

UIFont *text2Font = [UIFont fontWithName:@"HelveticaNeue-Medium" size:16];
NSMutableAttributedString *attributedString2 =
[[NSMutableAttributedString alloc] initWithString:text2 attributes:@{NSFontAttributeName : text2Font }];
NSMutableParagraphStyle *paragraphStyle2 = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle2 setLineSpacing:4];
[paragraphStyle2 setAlignment:NSTextAlignmentCenter];
[attributedString2 addAttribute:NSParagraphStyleAttributeName value:paragraphStyle2 range:NSMakeRange(0, [attributedString2 length])];

[attributedString1 appendAttributedString:attributedString2];

iOS 6中存在一个错误，该错误会导致在设置字体时忽略行高。请参见NSParagraphStyle行间距的答案，以及在Radar上进行更长时间的错误分析：UITextView忽略属性字符串中的最小/最大行高。

您可以使用此示例并按如下所示更改其实现：

[self enumerateAttribute:NSParagraphStyleAttributeName
                 inRange:NSMakeRange(0, self.length)
                 options:0
              usingBlock:^(id  _Nullable value, NSRange range, BOOL * _Nonnull stop) {
                  NSMutableParagraphStyle *paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];

                  //add your specific settings for paragraph
                  //...
                  //...

                  [self removeAttribute:NSParagraphStyleAttributeName range:range];
                  [self addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:range];
              }];