Windows Phone 8：消息框已停止工作？

Question

So im working on an application using the motion api and updating via event handles. The issue is i am having trouble getting the message box to show and i cant understand why. basic code below:

    public MainPage()
    {
        InitializeComponent();
        MessageBox.Show("welcome"); //box not showing
    }

    protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
    {

            motion = new Motion();
            motion.TimeBetweenUpdates = TimeSpan.FromMilliseconds(20);
            motion.CurrentValueChanged +=
                new EventHandler<SensorReadingEventArgs<MotionReading>>         (motion_CurrentValueChanged);

            motion.Start();

    }


    void motion_CurrentValueChanged(object sender, SensorReadingEventArgs<MotionReading> e)
    {
        Dispatcher.BeginInvoke(() => CurrentValueChanged(e.SensorReading));
    }



    private void CurrentValueChanged(MotionReading e)
    {
            Thickness mar = characterMain.Margin;

            txtblck1.Text = "Yaw " + e.Attitude.Yaw.ToString() + " Pitch " + e.Attitude.Pitch + " Roll " + e.Attitude.Roll;

            mar.Left = hor + (e.Attitude.Roll * 200);
            mar.Top = vert + (e.Attitude.Pitch * 200);
            characterMain.Margin = mar;

            bool col = engine1.CDetection_V1(characterMain.Margin.Left, characterMain.Margin.Top, characterMain.Width, characterMain.Height, BadGuy.Margin.Left, BadGuy.Margin.Top, BadGuy.Width, BadGuy.Height);
            if (col == true)
            {
                MessageBox.Show("hit");//this doesnt
                num.Text = "hit"; //this works
            }


    }

Answer 1

Okay so problem solved! Turns out that the problem was not my code or how vs was set up it was infact my phone! i had been testing on my 1020 and as a last resort before reinstalling vs2013 i decided to try another app that i knew had a message box on my phone! and noticed it wasnt appearing a simple restart fixed this and my code started working! so it looks like a bug in WP that must happen every now and then! Thanks to everyone for the help especially Romasz

Answer 2

尝试在页面的Loaded事件中使用Messagebox.Show() ，而不在构造函数中使用它。

Answer 3

Try using the following code.

protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        //Your logic
        MessageBox.Show("Welcome");
    }

Difference between using in OnNavigatedTo() and MainPage() is:

1. The code will runs only once in MainPage(){}. Eventhough you go back to the MainPage.xaml, the code will not run.
2. Whereas, the code in OnNavigatedTo() will runs everytime you navigate to MainPage.xaml.