多行导航栏标题

我试图在导航栏中设置标题标签以允许多行.我有自定义导航控制器代码,我将多行代码放入.我知道代码已经存在,但我的多行部分无效.

let titleLabel = UILabel()
titleLabel.frame = CGRectMake(0, 0, self.navigationBar.frame.width, self.navigationBar.frame.height * 2)
titleLabel.numberOfLines = 0
titleLabel.lineBreakMode = .ByWordWrapping

navigationItem.titleView = titleLabel

但是文本最后仍然没有结束.我也尝试将它放入单独的视图控制器本身,self.navigationController?.在前面添加navigationItem相同的结果.

我的代码中是否有一些东西会使标题标签不能使用多行？

以下是如何创建多行navigationBar标题的代码示例

let label: UILabel = UILabel(frame: CGRectMake(0, 0, 400, 50))
label.backgroundColor = UIColor.clearColor()
label.numberOfLines = 2
label.font = UIFont.boldSystemFontOfSize(16.0)
label.textAlignment = .Center
label.textColor = UIColor.whiteColor()
label.text = "This is a\nmultiline string for the navBar"
self.navigationItem.titleView = label

Swift 3.0:

let label = UILabel()
label.backgroundColor = .clear
label.numberOfLines = 2
label.font = UIFont.boldSystemFont(ofSize: 16.0)
label.textAlignment = .center
label.textColor = .white
label.text = "This is a\nmultiline string for the navBar"
self.navigationItem.titleView = label