ios - UINavigationBar 中的 AttributedString 不显示两行文本

Question

我正在尝试在我的 UINavigationBar 中设置两行标签。当我执行以下操作时，它只显示一行(换行符之前的部分)。

NSString *title = @"First line of title is bigger\nSecond line of title is smaller";
NSDictionary *attribute1 = @{NSForegroundColorAttributeName: [UIColor colorWithRed:148/255.0f green:147/255.0f blue:147/255.0f alpha:1],
                             NSFontAttributeName: [UIFont boldSystemFontOfSize: 14.0f]};
NSDictionary *attribute2 = @{NSForegroundColorAttributeName: [UIColor colorWithRed:148/255.0f green:147/255.0f blue:147/255.0f alpha:1],
                             NSFontAttributeName: [UIFont boldSystemFontOfSize: 10.0f]};
const NSRange line1Range = {0, 29};
const NSRange line2Range = {31, 30};

NSMutableAttributedString *attributedText =[[NSMutableAttributedString alloc] initWithString:title];
[attributedText setAttributes: attribute1 range:line1Range];
[attributedText setAttributes: attribute2 range:line2Range];

UILabel *label = [[UILabel alloc] init];
label.attributedText=attributedText;
self.navigationItem.titleView = label;
[self.navigationItem.titleView sizeToFit];

为了比较，下面显示了两条线。以下仅供比较。顶级版本是我需要的。

UILabel *label = [[UILabel alloc] init];
label.backgroundColor = [UIColor clearColor];
label.numberOfLines = 2;
label.font = [UIFont boldSystemFontOfSize: 14.0f];
label.textColor = [UIColor colorWithRed:148/255.0f green:147/255.0f blue:147/255.0f alpha:1];
label.text = @"First line of title is bigger\nSecond line of title is smaller";

self.navigationItem.titleView = label;
[self.navigationItem.titleView sizeToFit];

对于让顶级版本正常工作有什么帮助吗？

Answer 1

似乎调用 label.sizeToFit() before self.navigationItem.titleView = label 正确显示 NSAttributedString 标题。

( swift ，iOS8.1，XCode 6.1.1)