Xamarin.Forms UWP-登录时启动应用程序

Question

I'm trying to launch my app when the user logs in to Windows. I have the appropriate Extension ( StartupTask ) set in Package.appxmanifest , and I can get the app to launch when I log in to Windows, as expected. However, the app crashes after showing the Splash screen for about a second or two.

In my App.xaml.cs file, I have overridden the OnLaunched (called when the user launches the app) and OnActivated (called when the system launches the app after Windows login). Both call the same function to initialize my app; however, the app crashes only when the app is initialized from the OnActivated function. When initialized from OnLaunched , it works as expected. Here is the relevant code, from App.xaml.cs :

// Called when the user launches the app
protected override void OnLaunched(LaunchActivatedEventArgs e)
{
    // Calling InitializeApp here, the app launches without problem
    InitializeApp(e);
}

// Called when the system launches the app after Windows login
protected override void OnActivated(IActivatedEventArgs e)
{
    base.OnActivated(e);
    // Calling InitializeApp here will cause the app to crash
    InitializeApp((LaunchActivatedEventArgs)e);
}

// initialize the app
async void InitializeApp(LaunchActivatedEventArgs e)
{
    Frame rootFrame = Window.Current.Content as Frame;

    // Do not repeat app initialization when the Window already has content,
    // just ensure that the window is active
    if (rootFrame == null)
    {
        // Create a Frame to act as the navigation context and navigate to the first page
        rootFrame = new Frame();
        rootFrame.NavigationFailed += OnNavigationFailed;

        var assembliesToInclude = new List<Assembly>()
        {
            typeof(CachedImage).GetTypeInfo().Assembly,
            typeof(CachedImageRenderer).GetTypeInfo().Assembly
        };
        Xamarin.Forms.Forms.Init(e, assembliesToInclude);

        // Place the frame in the current Window
        Window.Current.Content = rootFrame;
    }

    if (rootFrame.Content == null)
    {
        // When the navigation stack isn't restored navigate to the first page,
        // configuring the new page by passing required information as a navigation
        // parameter
        rootFrame.Navigate(typeof(MainPage), e.Arguments);
    }

    // Ensure the current window is active
    Window.Current.Activate();

    if (session == null)
    {
        // prevent the app from stopping when minimized
        session = new ExtendedExecutionSession();
        session.Reason = ExtendedExecutionReason.Unspecified;
        session.Revoked += (s, a) => { };
        var result = await session.RequestExtensionAsync();

        if (result == ExtendedExecutionResult.Denied)
            System.Diagnostics.Debug.WriteLine("EXTENDED EXECUTION DENIED");
    }
}

Answer 1

The problem is that you are trying to cast the IActivatedEventArgs to LaunchActivatedEventArgs , but when startup activation happens, the type is actually StartupTaskActivatedEventArgs .

Luckily, you actually need the e parameter only for Xamarin.Forms.Forms.Init which actually accepts IActivatedEventArgs , so you can just change the parameter of InitializeApp to be IActivatedEventArgs and remove the cast to LaunchActivatedEventArgs in OnActivated .