Xamarin窗体阻止用户后退键

在我的Xamarin表单应用程序中，当用户单击主页上的后退按钮时，我希望显示一条确认消息。有没有办法做到这一点？ 我在主页中重写了OnBackButtonPressed方法。但当按back键时，应用程序仍将关闭。这是我的密码

protected override bool OnBackButtonPressed ()
    {
        //return base.OnBackButtonPressed ();
        return false;
    }

---

您可以覆盖任何Xamarin.Form页面的OnBackButtonPressed。但它只适用于Android和Windows Phone设备中的物理按钮

    protected override bool OnBackButtonPressed () {
        DisplayAlert("title","message","ok");
        return true;
    }

对于虚拟渲染器，您需要创建CustomRenders并拦截click处理程序。在iOS中，这可能很棘手，因为用户可以回去做其他动作（例如刷卡手势）。一旦你截获它，你只需要创建你的确认消息（我假设你知道怎么做）

对于iOS，您可以执行以下操作：

[assembly: ExportRenderer (typeof (YourPage), typeof (YourPageRenderer))]
namespace YourNamespace {
public class YourPageRenderer : PageRenderer {

    public override void ViewWillAppear (bool animated) {
        base.ViewWillAppear (animated);
        Action goBack = () => page.DisplayAlert("title","message","ok");

        var backButton = new NavBackButton (goBack);
        navigationItem.LeftBarButtonItem = new UIBarButtonItem (backButton);
    }
}

  public class NavBackButton : UIView {
    public NavBackButton (Action onButtonPressed) {
        SetButton (onButtonPressed);
    }

    UILabel text;
    UIImageView arrow;

    void SetButton(Action onButtonPressed){
        arrow = new UIImageView(new CGRect(-25,0, 50, 50)) { 
            Image = new UIImage("Images/back").ImageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)
        };
        arrow.TintColor = Colors.DarkGreen.ToUIColor ();

        text = new UILabel(new CGRect(arrow.Frame.Width + arrow.Frame.X -15, arrow.Frame.Height /2 - 10, 40, 20))  { Text = "Back" };
        text.TextColor = Colors.DarkGreen.ToUIColor ();
        Frame = new CGRect(0,0,text.Frame.Size.Width + arrow.Frame.Width, arrow.Frame.Height);
        AddSubviews (new UIView[] { arrow, text });

        var tapGesture = new UITapGestureRecognizer (onButtonPressed);
        AddGestureRecognizer (tapGesture);

    }
    public override void TouchesBegan (Foundation.NSSet touches, UIEvent evt) {
        base.TouchesBegan (touches, evt);
        text.TextColor =  UIColor.YourColor;
        arrow.TintColor =  UIColor.YourColor;
    }

    public override void TouchesEnded (Foundation.NSSet touches, UIEvent evt){
        base.TouchesEnded (touches, evt);
        arrow.TintColor = UIColor.YourColor;
        text.TextColor = UIColor.YourColor;
    }

}
}

---

PS您需要提供一个箭头图像（“Images/back”）

I wnat以等待方法DisplayAlert（标题，消息，“Yes”，“No”）获得结果。但是在overided方法中无法做到这一点您可以做到，但是您需要将被重写的方法标记为async。请注意，DisplayAlert只返回任务，而不返回任务。如果你想更深入地了解这一点，请问另一个问题，如果这个答案对你有用，请标记为正确。