显示导致SplashScreen的InvalidOperationException

Question

问题

我有一个MVVM应用程序，它使用Caliburn.Micro作为MVVM框架，MEF用于“依赖注入”(如我所知，它不是一个严格意义上的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，基于MEF在应用程序启动期间所做的组合的数量，因此我想使用一个动画启动屏幕。

下面我将概述我的当前代码，该代码显示单独线程上的启动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; }
    }
}

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

误差

这段代码似乎运行良好，因为它在后台线程上启动启动屏幕，启动动画作品等等。但是，当代码返回引导程序时，行。

DisplayRootViewFor<IMainWindow>(); 

引发带有以下消息的InvalidOperationException

调用线程无法访问此对象，因为其他线程拥有该对象。

堆栈跟踪是

在System.Windows.Threading.Dispatcher.VerifyAccess() at 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:line 269在MahApps.Metro.Controls.MetroWindow.ThemeManagerOnIsThemeChanged(Object发件人，OnThemeChangedEventArgs e在d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\MetroWindow.cs:line 962在System.EventHandler1. in (对象发送方，( MahApps.Metro.Controls.SafeRaise.RaiseT in d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\SafeRaise.cs:line 26 at MahApps.Metro.ThemeManager.OnThemeChanged(Accent newAccent，AppTheme newTheme)在d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\ThemeManager\ThemeManager.cs:line 591 at MahApps.Metro.ThemeManager.ChangeAppStyle(ResourceDictionary resources，Tuple`2‘2 oldThemeInfo，AppTheme newAccent，d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\ThemeManager\ThemeManager.cs:line 407 at MahApps.Metro.ThemeManager.ChangeAppStyle(Application app，AppTheme newTheme(重音newAccent )( d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\ThemeManager\ThemeManager.cs:line 345 at Augur.Core.Themes.ThemeManager.SetCurrentTheme(String name) F:\Camus\Augur\Src\Augur\Core\Themes\ThemeManager.cs:line 46 at Augur.Modules.Shell.ViewModels.ShellViewModel.OnViewLoaded(Object view) ( F:\Camus\Augur\Src\Augur\Modules\Shell\ViewModels\ShellViewModel.cs:line 73 at Caliburn.Micro.XamlPlatformProvider.<>c_ )_DisplayClass11_0.b__0(Object s，在Caliburn.Micro.View.<>c__DisplayClass8_0.b__0(Object s，RoutedEventArgs e)在System.Windows.EventRoute.InvokeHandlersImpl(Object源，RoutedEventArgs args，Boolean (在System.Windows.UIElement.RaiseEventImpl(DependencyObject发件人，RoutedEventArgs args)在System.Windows.BroadcastEventHelper.BroadcastEvent(DependencyObject根，( System.Windows.BroadcastEventHelper.BroadcastLoadedEvent(Object root) )在MS.Internal.LoadedOrUnloadedOperation.DoWork() at System.Windows.Media.MediaContext.FireLoadedPendingCallbacks() at System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks() at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget( System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget) at System.Windows.Interop.HwndTarget.OnResize() at System.Windows.Interop.HwndTarget.OnResize() at System.Windows.Interop.HwndTarget.HandleMessage(WindowMessage msg，IntPtr wParam，IntPtr lParam ) at System.Windows.Interop.HwndSource.HwndTargetFilterMessage(IntPtr hwnd，Int32 msg，IntPtr IntPtr，，在MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o的MS.Win32.HwndWrapper.WndProc(IntPtr hwnd，Int32 msg，IntPtr wParam，IntPtr lParam，Boolean& handled)上的System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate回调，对象args，Int32 numArgs在System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object源，委托回调，对象args，Int32 numArgs，委托发展)在System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority优先级，TimeSpan超时值，委托方法，对象args，numArgs)在( hwnd，msg，，IntPtr lParam)

尝试解决方案

我试图将执行DisplayRootViewFor<IMainWindow>();的代码更改为使用dispatcher，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。所有这些都会抛出相同的异常。

问题

1. 如何调用DisplayRootViewFor<IMainWindow>()方法并避免此异常？
2. 这种显示动画的方法是合法的吗？

耽误您时间，实在对不起。

编辑。我从了不起的汉斯·帕桑特( Hans https://stackoverflow.com/a/4078528/626442 )那里发现了这个答案。有鉴于此，我尝试添加应用程序static App() { } ctor。

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

但(可能并不令人意外)这对我没有帮助。同一地点同样的例外..。

Answer 1

您正在一个新的后台线程上创建一个SplashScreenView实例，但随后从主UI线程调用ThemeManager类中的MetroThemeManager.ChangeAppStyle。

因为MetroWindow类是您的SplashScreenView的父类，所以不能阻止它在内部订阅ThemeManager.IsThemeChanged事件，这是通过在ThemeManager类中调用MetroThemeManager.ChangeAppStyle来触发的。

由于ThemeManager.IsThemeChanged事件处理程序在MetroWindow中的代码不能在主UI线程上执行，这与线程启动屏幕不同，所以您应该从标准的Window类派生SplashScreenView以避免对MetroWindow的依赖，或者2在SplashScreenView还活着时避免调用MetroThemeManager.ChangeAppStyle。

注释掉两行代码将消除冲突，请参见下面的行。但是很明显，实际的解决方案需要在另一个层次上完成，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);