Windows Phone 7 Cancel hardware back button not working

Question

I need to cancel the device back button event. I have tried the solution posted in Control press "back button" and disable close the application using a dialog for confirm - wp7, but it is not working for me. Am I doing something wrong? The application always exits whether ok or cancel is selected from the dialog box.

Here is my code...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using System.IO;
using System.Windows.Media.Imaging;
using System.Windows.Resources;


namespace GodTools
{
    public partial class MainPage : PhoneApplicationPage
    {
        // Constructor
        public MainPage()
        {
            InitializeComponent();
            this.CordovaView.Loaded += CordovaView_Loaded;

            BackKeyPress += OnBackKeyPressed;

        }

        private void CordovaView_Loaded(object sender, RoutedEventArgs e)
        {
            this.CordovaView.Loaded -= CordovaView_Loaded;
            // first time load will have an animation
            Storyboard _storyBoard = new Storyboard();
            DoubleAnimation animation = new DoubleAnimation()
            {
                From = 0,
                Duration = TimeSpan.FromSeconds(0.6),
                To = 90
            };
            Storyboard.SetTarget(animation, SplashProjector);
            Storyboard.SetTargetProperty(animation, new PropertyPath("RotationY"));
            _storyBoard.Children.Add(animation);
            _storyBoard.Begin();
            _storyBoard.Completed += Splash_Completed;
        }

        void Splash_Completed(object sender, EventArgs e)
        {
            (sender as Storyboard).Completed -= Splash_Completed;
            LayoutRoot.Children.Remove(SplashImage);
        }

        void OnBackKeyPressed(object sender, System.ComponentModel.CancelEventArgs e)
        {
            var result = MessageBox.Show("Do you want to exit?", "Attention!",
                                          MessageBoxButton.OKCancel);

            if (result == MessageBoxResult.OK)
            {
                // Do not cancel navigation
                return;
            }
            e.Cancel = true;
        }
    }
}

see also, same problem from the Cordova side "backbutton" event won't fire

Answer 1

For your information: If you write an application (not an XNA game) you shoul avoid canceling back button. Otherwise your app will be canceled on passing Marketplace sertification.

Also you can override OnBackKeyPress method with the same code;

protected override void OnBackKeyPress(CancelEventArgs e)
        {
            var result = MessageBox.Show("Do you want to exit?", "Attention!",
                                          MessageBoxButton.OKCancel);

            if (result == MessageBoxResult.OK)
            {
                base.OnBackKeyPress(e);
                return;
            }
            e.Cancel = true;
        }

update

I've just created a new 'Silverlight for windows phone" solution. Opened MainPage.xaml.cs file and added this code to it:

// Constructor
public MainPage()
{
    InitializeComponent();
    BackKeyPress += OnBackKeyPressed;
}

void OnBackKeyPressed(object sender, System.ComponentModel.CancelEventArgs e)
{
    var result = MessageBox.Show("Do you want to exit?", "Attention!",
                                  MessageBoxButton.OKCancel);

    if (result == MessageBoxResult.OK)
    {
        // Do not cancel navigation
        return;
    }
    e.Cancel = true;
}

so there is only one page in this project. And it works. The target platform is Windows Phone OS 7.1, I've checked it on Mango device and on the standard emulator. I think the problem is somewhere else. Maybe some code crashes you application while you are trying to cancel back event?

Please, try to check it on new simple project.