UIAlertController 自定义字体在 iOS 上不起作用

UIAlertController 自定义字体不起作用。

下面的代码是一个函数ShowActionSheetAsync, show ActionSheet。 此时我想改变字体ActionSheet。我尝试了多种方法，但效果并不好。有好的解决办法吗？

public Task<bool> ShowActionSheetAsync()
{
    var source = new TaskCompletionSource<bool>();
    var alert = new UIAlertController
    {
        Title = "title"
    };
    alert.AddAction(UIAlertAction.Create(
            "button1",
            UIAlertActionStyle.Default,
            _ => source.SetResult(true)));
    alert.AddAction(UIAlertAction.Create(
        "cancel",
        UIAlertActionStyle.Cancel,
        _ => source.SetResult(false)));

    // [Block 1]
    var viewController = UIApplication.SharedApplication.KeyWindow.RootViewController;
    ViewController.PresentViewController(alert, true, delegate
    {
        // [Block 2]
    });

    // [Block 3]
    return source.Task;
}

第一次尝试以下代码无法正常工作。

• 当我把代码放在[Block 1] or [Block 2]

  • 它根本不起作用

• 当我把代码放在[Block 3]

  • 仅适用于首次演出时ActionSheet。从第二次开始就不行了

UILabel.AppearanceWhenContainedIn(typeof(UIActionSheet)).Font = UIFont.FromName(StyleResources.MediumFontName, 20);

第二次尝试下面的代码也无法正常工作。

• 当我把代码放在[Block 2]

  • 显示默认字体一小段时间后，显示自定义字体

• 当我把代码放在[Block 3]

  • 它只适用于cancel button

FindDescendantViews<UILabel>()是一个扩展方法UIView并返回适当类型的所有子视图。

var labels = alert.View.FindDescendantViews<UILabel>();
foreach (var label in labels)
{
    label.Font = UIFont.FromName(StyleResources.MediumFontName, 20);
}

UIAlertController UILabels字体和颜色可以通过 KVC 设置attributedTitle钥匙。使用这个[Block 3]

func changeAlert(alert: UIAlertController, backgroundColor: UIColor, textColor: UIColor, buttonColor: UIColor?) {
    let view = alert.view.firstSubview().firstSubview()
    view.backgroundColor = backgroundColor
    view.layer.cornerRadius = 10.0

    // set color to UILabel font
    setSubviewLabelsToTextColor(textColor, view: view)

    // set font to alert via KVC, otherwise it'll get overwritten
    let titleAttributed = NSMutableAttributedString(
        string: alert.title!,
        attributes: [NSFontAttributeName:UIFont.boldSystemFontOfSize(17)])
    alert.setValue(titleAttributed, forKey: "attributedTitle")


    let messageAttributed = NSMutableAttributedString(
        string: alert.message!,
        attributes: [NSFontAttributeName:UIFont.systemFontOfSize(13)])
    alert.setValue(messageAttributed, forKey: "attributedMessage")


    // set the buttons to non-blue, if we have buttons
    if let buttonColor = buttonColor {
        alert.view.tintColor = buttonColor
    }
}

func setSubviewLabelsToTextColor(textColor: UIColor, view:UIView) {
    for subview in view.subviews {
        if let label = subview as? UILabel {
            label.textColor = textColor
        } else {
            setSubviewLabelsToTextColor(textColor, view: subview)
        }
    }
}