哦，在2021年，我被一个标签文本困住了，一个小时都不能换行，然后意识到我忘记设置标签的宽度，WTF。

let stepLabel: UILabel = {
    let label = UILabel()
    label.translatesAutoresizingMaskIntoConstraints = false
    label.textAlignment = .center
    label.lineBreakMode = .byWordWrapping
    label.numberOfLines = 0
    label.text = "Put your device and computer under same Wi-Fi network."
    
    return label
}()

override func viewDidLoad() {
    super.viewDidLoad()
    
    view.backgroundColor = .white
    view.addSubview(stepLabel)

    NSLayoutConstraint.activate([
        stepLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor),
        stepLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor),
        stepLabel.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.7)
    ])
}

设置换行模式为换行，行数为0:

// Swift
textLabel.lineBreakMode = .byWordWrapping
textLabel.numberOfLines = 0

// Objective-C
textLabel.lineBreakMode = NSLineBreakByWordWrapping;
textLabel.numberOfLines = 0;

// C# (Xamarin.iOS)
textLabel.LineBreakMode = UILineBreakMode.WordWrap;
textLabel.Lines = 0;  

恢复旧答案(供参考和开发者愿意支持iOS 6.0以下):

textLabel.lineBreakMode = UILineBreakModeWordWrap;
textLabel.numberOfLines = 0;

另一方面:两个enum值都为0。

让我们试试这个

textLabel.lineBreakMode = NSLineBreakModeWordWrap; // UILineBreakModeWordWrap deprecated     
textLabel.numberOfLines = 0;                          

在这个函数中，传递你想在label中赋值的字符串，并传递字体大小来代替self。activityFont和传递标签宽度的地方235，现在你得到标签高度根据你的字符串。 它会工作得很好。

-(float)calculateLabelStringHeight:(NSString *)answer
{
    CGRect textRect = [answer boundingRectWithSize: CGSizeMake(235, 10000000) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:self.activityFont} context:nil];
    return textRect.size.height;

}

在c#中，这在UITableViewCell中为我工作。

        UILabel myLabel = new UILabel();
        myLabel.Font = UIFont.SystemFontOfSize(16);
        myLabel.Lines = 0;
        myLabel.TextAlignment = UITextAlignment.Left;
        myLabel.LineBreakMode = UILineBreakMode.WordWrap;
        myLabel.MinimumScaleFactor = 1;
        myLabel.AdjustsFontSizeToFitWidth = true;

       myLabel.InvalidateIntrinsicContentSize();
       myLabel.Frame = new CoreGraphics.CGRect(20, mycell.ContentView.Frame.Y + 20, cell.ContentView.Frame.Size.Width - 40, mycell.ContentView.Frame.Size.Height);
       myCell.ContentView.AddSubview(myLabel);

我认为这里的重点是:-

            myLabel.TextAlignment = UITextAlignment.Left;
            myLabel.LineBreakMode = UILineBreakMode.WordWrap;
            myLabel.MinimumScaleFactor = 1;
            myLabel.AdjustsFontSizeToFitWidth = true;

UILabel *helpLabel = [[UILabel alloc] init];
NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:label];
helpLabel.attributedText = attrString;
// helpLabel.text = label;

helpLabel.textAlignment = NSTextAlignmentCenter;
helpLabel.lineBreakMode = NSLineBreakByWordWrapping;
helpLabel.numberOfLines = 0;

出于某些原因，它在iOS 6中不为我工作，不知道为什么。尝试了带和不带带属性的文本。任何建议。