显示 SplashScreen 导致 InvalidOperationException

Question

问题

我有一个 MVVM 应用程序，它使用 Caliburn.Micro 作为 MVVM 框架和 MEF 用于“依赖注入”（引用我知道它不是严格意义上的 DI 容器）。这个大型应用程序的合成过程开始花费越来越多的时间，这取决于 MEF 在应用程序启动期间正在进行的合成数量，因此我想使用动画启动屏幕。

下面我将概述我当前的代码，该代码在单独的线程上显示初始屏幕并尝试启动主应用程序

public class Bootstrapper : BootstrapperBase
{
    private List<Assembly> priorityAssemblies;
    private ISplashScreenManager splashScreenManager;

    public Bootstrapper()
    {
        Initialize();
    }

    protected override void Configure()
    {
        var directoryCatalog = new DirectoryCatalog(@"./");
        AssemblySource.Instance.AddRange(
             directoryCatalog.Parts
                  .Select(part => ReflectionModelServices.GetPartType(part).Value.Assembly)
                  .Where(assembly => !AssemblySource.Instance.Contains(assembly)));

        priorityAssemblies = SelectAssemblies().ToList();
        var priorityCatalog = new AggregateCatalog(priorityAssemblies.Select(x => new AssemblyCatalog(x)));
        var priorityProvider = new CatalogExportProvider(priorityCatalog);

        var mainCatalog = new AggregateCatalog(
            AssemblySource.Instance
                .Where(assembly => !priorityAssemblies.Contains(assembly))
                .Select(x => new AssemblyCatalog(x)));
        var mainProvider = new CatalogExportProvider(mainCatalog);

        Container = new CompositionContainer(priorityProvider, mainProvider);
        priorityProvider.SourceProvider = Container;
        mainProvider.SourceProvider = Container;

        var batch = new CompositionBatch();

        BindServices(batch);
        batch.AddExportedValue(mainCatalog);

        Container.Compose(batch);
    }

    protected virtual void BindServices(CompositionBatch batch)
    {
        batch.AddExportedValue<IWindowManager>(new WindowManager());
        batch.AddExportedValue<IEventAggregator>(new EventAggregator());
        batch.AddExportedValue(Container);
        batch.AddExportedValue(this);
    }


    protected override object GetInstance(Type serviceType, string key)
    {
        String contract = String.IsNullOrEmpty(key) ?
            AttributedModelServices.GetContractName(serviceType) :
            key;
        var exports = Container.GetExports<object>(contract);

        if (exports.Any())
            return exports.First().Value;

        throw new Exception(
            String.Format("Could not locate any instances of contract {0}.", contract));
    }

    protected override IEnumerable<object> GetAllInstances(Type serviceType)
    {
        return Container.GetExportedValues<object>(
            AttributedModelServices.GetContractName(serviceType));
    }

    protected override void BuildUp(object instance)
    {
        Container.SatisfyImportsOnce(instance);
    }

    protected override void OnStartup(object sender, StartupEventArgs suea)
    {
        splashScreenManager = Container.GetExportedValue<ISplashScreenManager>();
        splashScreenManager.ShowSplashScreen();

        base.OnStartup(sender, suea);
        DisplayRootViewFor<IMainWindow>(); // HERE is the Problem line.

        splashScreenManager.CloseSplashScreen();
    }

    protected override IEnumerable<Assembly> SelectAssemblies()
    {
        return new[] { Assembly.GetEntryAssembly() };
    }

    protected CompositionContainer Container { get; set; }

    internal IList<Assembly> PriorityAssemblies
    {
        get { return priorityAssemblies; }
    }
}

我的ISplashScreenManager 实现是

[Export(typeof(ISplashScreenManager))]
[PartCreationPolicy(CreationPolicy.NonShared)]
public class SplashScreenManager : ISplashScreenManager
{
    private ISplashScreenViewModel splashScreen;
    private Thread splashThread;
    private Dispatcher splashDispacher;

    public void ShowSplashScreen()
    {
        splashDispacher = null;
        if (splashThread == null)
        {
            splashThread = new Thread(new ThreadStart(DoShowSplashScreen));
            splashThread.SetApartmentState(ApartmentState.STA);

            splashThread.IsBackground = true;
            splashThread.Name = "SplashThread"; 

            splashThread.Start();
            Log.Trace("Splash screen thread started");

            Application.Current.ShutdownMode = ShutdownMode.OnMainWindowClose;
            Application.Current.MainWindow = null;
        }
    }

    private void DoShowSplashScreen()
    {
        splashScreen = IoC.Get<ISplashScreenViewModel>();

        splashDispacher = Dispatcher.CurrentDispatcher;
        SynchronizationContext.SetSynchronizationContext(
            new DispatcherSynchronizationContext(splashDispacher));

        splashScreen.Closed += (s, e) =>
            splashDispacher.BeginInvokeShutdown(DispatcherPriority.Background);
        splashScreen.Show();

        Dispatcher.Run();
        Log.Trace("Splash screen shown and dispatcher started");
    }

    public void CloseSplashScreen()
    {
        if (splashDispacher != null)
        {
            splashDispacher.BeginInvokeShutdown(DispatcherPriority.Send);
            splashScreen.Close();
            Log.Trace("Splash screen close requested");
        }
    }

    public ISplashScreenViewModel SplashScreen
    {
        get { return splashScreen; }
    }
}

ISplashScreenViewModel.Show() 和 ISplashScreenViewModel.Close() 方法分别显示和关闭相应的视图。

错误

这段代码似乎运行良好，因为它在后台线程上启动启动画面并且启动动画工作等。但是，当代码返回到引导程序时，该行

DisplayRootViewFor<IMainWindow>(); 

抛出 InvalidOperationException 并显示以下消息

调用线程无法访问此对象，因为另一个线程拥有它。

堆栈跟踪是

在 System.Windows.Threading.Dispatcher.VerifyAccess() 在 System.Windows.DependencyObject.GetValue(DependencyProperty dp) 在 MahApps.Metro.Controls.MetroWindow.get_Flyouts() 在 d:\projects\git\MahApps.Metro \src\MahApps.Metro\MahApps.Metro.Shared\Controls\MetroWindow.cs：D:\projects\git\MahApps.Metro\ 中 MahApps.Metro.Controls.MetroWindow.ThemeManagerOnIsThemeChanged(Object sender, OnThemeChangedEventArgs e) 的第 269 行src\MahApps.Metro\MahApps.Metro.Shared\Controls\MetroWindow.cs：System.EventHandler1.Invoke 的第 962 行（对象发送者，TEventArgs e） 在 d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\SafeRaise 中的 MahApps.Metro.Controls.SafeRaise.Raise[T](EventHandler1 eventToRaise, Object sender, T args) .cs: d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\ThemeManager\ThemeManager.cs 中 MahApps.Metro.ThemeManager.OnThemeChanged(Accent newAccent, AppTheme newTheme) 的第 26 行： d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\ThemeManager 中 MahApps.Metro.ThemeManager.ChangeAppStyle(ResourceDictionary resources, Tuple`2 oldThemeInfo, Accent newAccent, AppTheme newTheme) 的第 591 行\ThemeManager.cs：D:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\ThemeManager 中 MahApps.Metro.ThemeManager.ChangeAppStyle(Application app, Accent newAccent, AppTheme newTheme) 的第 407 行\ThemeManager.cs：Augur.Core.Themes.ThemeManager.SetCurrentTheme（字符串名称）的第 345 行在 F:\Camus\Augur\Src\Augur\Core\Themes\ThemeManager.cs：Augur.Modules.Shell 的第 46 行。视图模块els.ShellViewModel.OnViewLoaded(Object view) in F:\Camus\Augur\Src\Augur\Modules\Shell\ViewModels\ShellViewModel.cs:Caliburn.Micro.XamlPlatformProvider 的第 73 行。c__DisplayClass11_0.b__0(Object s, RoutedEventArgs e) 在 Caliburn.Micro.View.c__DisplayClass8_0.b__0(Object s, RoutedEventArgs e) 在 System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) 在 System.Windows.UIElement.RaiseEventImpl(DependencyObject sender , RoutedEventArgs args) 在 System.Windows.BroadcastEventHelper.BroadcastEvent(DependencyObject root, RoutedEvent routedEvent) 在 System.Windows.BroadcastEventHelper.BroadcastLoadedEvent(Object root) 在 MS.Internal.LoadedOrUnloadedOperation.DoWork() 在 System.Windows.Media.MediaContext。 FireLoadedPendingCallbacks() 在 System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks() 在 System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget) 在 System.Windows.Media.MediaContext.RenderMessageHandler (Object resizedCompositionTarget) 在 System.Windows.Interop.HwndTarget.OnResize() 在 System.Windows.Interop.HwndTarget.HandleMessage(WindowMessage msg, IntPtr wparam, IntPtr lparam) 在 System.Windows.Interop.HwndSource.HwndTargetFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean&handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean&handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System .Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) 在 System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler) 在 System.Windows.Threading .Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)

尝试的解决方案

我已尝试将执行DisplayRootViewFor<IMainWindow>(); 的代码更改为使用调度程序，如下所示

base.OnStartup(sender, suea);
Application.Current.Dispatcher.Invoke(() => DisplayRootViewFor<IMainWindow>()); // Still throws the same exception.

和

base.OnStartup(sender, suea);
Application.Current.Dispatcher.BeginInvoke(
    new System.Action(delegate { DisplayRootViewFor<IMainWindow>(); })); // Still throws the same exception.

甚至

TaskScheduler guiScheduler = TaskScheduler.FromCurrentSynchronizationContext();

splashScreenManager = Container.GetExportedValue<ISplashScreenManager>();
splashScreenManager.ShowSplashScreen();

Task.Factory.StartNew(() =>
{
    base.OnStartup(sender, suea);
    DisplayRootViewFor<IMainWindow>();
}, CancellationToken.None, 
   TaskCreationOptions.None, 
   guiScheduler);

试图强制使用 Gui MainThread。以上所有都抛出相同的异常。

问题

1. 如何调用DisplayRootViewFor<IMainWindow>() 方法并避免此异常？

2. 这种显示动画飞溅的方法是否合法？

感谢您的宝贵时间。

---

编辑。我从很棒的 Hans Passant https://stackoverflow.com/a/4078528/626442 那里发现了这个答案。鉴于此，我尝试添加应用程序static App() { }ctor。

static App()
{
    // Other stuff.
    Microsoft.Win32.SystemEvents.UserPreferenceChanged += delegate { };
}

但是（可能不出所料）这对我没有帮助。相同位置的相同异常...

Answer 1

您正在一个新的后台线程上创建SplashScreenView 的实例，但随后在主 UI 线程的ThemeManager 类中调用MetroThemeManager.ChangeAppStyle。

因为MetroWindow 类是您的SplashScreenView 的父类，您无法阻止它在内部订阅您通过在ThemeManager 类中调用MetroThemeManager.ChangeAppStyle 触发的ThemeManager.IsThemeChanged 事件。

由于MetroWindow 中的ThemeManager.IsThemeChanged 事件处理程序的代码无法在不同于创建的线程启动屏幕的主 UI 线程上执行，因此您应该 [1] 从标准 @ 派生您的 SplashScreenView 987654332@ 类以避免依赖于 MetroWindow 或 [2] 避免在您的 SplashScreenView 还活着时调用 MetroThemeManager.ChangeAppStyle。

注释掉两行代码就是删除违规行为，请参见下面的行。但显然，实际的解决方案需要在另一个层面上完成，见上文。

// this line is causing violation due to hidden dependency
MetroThemeManager.ChangeAppStyle(Application.Current, metroAccent, metroTheme);

// this line is causing an error when closing the splash screen
splashDispacher.BeginInvokeShutdown(DispatcherPriority.Send);