我正在努力将 Xamarin.Forms 应用程序迁移到毛伊岛。在 MauiProgram 中，我们调用 MauiAppBuilder.UsePrism()，在 PrismAppBuilder 上调用 .RegisterTypes() 来注册服务和页面以进行导航。我们已确认服务正在初始化。最后，在 .OnAppStart 中，我们现在使用 .CreateWindow()。
.CreateWindow(async (container, navigation) =>
{
AppCenter.Start("android=guid;ios=guid",
typeof(Analytics), typeof(Crashes));
var result = await navigation.NavigateAsync("/AppInitPage");
if (!result.Success)
{
HandleNavigationError(result.Exception);
}
})
这会导致导航不成功并导致以下异常： Microsoft.Maui.Controls.InvalidNavigationException：“预期导航失败。尚未创建根窗口。'
PrismAppBuilder：
.UsePrism(prism =>
prism
#if ANDROID
.RegisterTypes(Platforms.Android.PlatformRegistrations.RegisterPlatformTypes)
#endif
.RegisterTypes(containerRegistry =>
{
Barrel.ApplicationId = AppInfo.Current.PackageName;
//Register all of the services
containerRegistry.RegisterInstance<IPreferences>(Preferences.Default);
containerRegistry.RegisterInstance<IConnectivity>(Connectivity.Current);
containerRegistry.RegisterInstance<IAppInfo>(AppInfo.Current);
containerRegistry.RegisterInstance<IDeviceInfo>(DeviceInfo.Current);
containerRegistry.RegisterInstance<IVersionTracking>(VersionTracking.Default);
containerRegistry.RegisterSingleton<IAppSettings, AppSettings>();
containerRegistry.RegisterSingleton<IDb, Db>();
containerRegistry.RegisterSingleton<IAPI, API>();
containerRegistry.RegisterSingleton<ISyncManager, SyncManager>();
containerRegistry.RegisterSingleton<ISyncWorker, SyncWorker>();
containerRegistry.Register<IAuthentication, Authentication>();
containerRegistry.Register<IEncryptDecrypt, StringEncryptor>();
containerRegistry.Register<IHelpers, Helpers>();
//Register Pages
containerRegistry.RegisterForNavigation<ThemedNavigationPage>("NavigationPage");
containerRegistry.RegisterForNavigation<AboutPage>();
containerRegistry.RegisterForNavigation<AppInitPage>();
containerRegistry.RegisterForNavigation<TermsOfServicePage>();
containerRegistry.RegisterForNavigation<LoginPage>();
containerRegistry.RegisterForNavigation<CustomerSearchPage>();
containerRegistry.RegisterForNavigation<SettingsPage, SettingsPageViewModel>();
containerRegistry.RegisterForNavigation<CustomerPage>();
containerRegistry.RegisterForNavigation<FilesPage>();
containerRegistry.RegisterForNavigation<PhotoPage>();
containerRegistry.RegisterForNavigation<CustomerContactPage>();
containerRegistry.RegisterForNavigation<AssetPage>();
containerRegistry.RegisterForNavigation<ProductPage>();
//containerRegistry.RegisterGlobalNavigationObserver();
App.Container = containerRegistry.GetContainer();
App.Container.Resolve<IDb>().InitializeTables();
})
.AddGlobalNavigationObserver(context => context.Subscribe(x =>
{
if (x.Type == NavigationRequestType.Navigate)
Console.WriteLine($"Navigation: {x.Uri}");
else
Console.WriteLine($"Navigation: {x.Type}");
var status = x.Cancelled ? "Cancelled" : x.Result.Success ? "Success" : "Failed";
Console.WriteLine($"Result: {status}");
if (status == "Failed" && !string.IsNullOrEmpty(x.Result?.Exception?.Message))
Console.Error.WriteLine(x.Result.Exception.Message);
}))
.OnInitialized(_ =>
{
Microsoft.Maui.ApplicationModel.VersionTracking.Track();
})
.CreateWindow(async (container, navigation) =>
{
AppCenter.Start("android=guid;ios=guid",
typeof(Analytics), typeof(Crashes));
var result = await navigation.NavigateAsync("/AppInitPage");
if (!result.Success)
{
HandleNavigationError(result.Exception);
}
})
);
异常堆栈：
[DOTNET] Navigation: http://localhost/AppInitPage
[DOTNET] Result: Failed
[DOTNET] A dependency issue occurred while resolving the ViewModel. Check the InnerException for the ContainerResolutionException
[DOTNET] Prism.Navigation.NavigationException: A dependency issue occurred while resolving the ViewModel. Check the InnerException for the ContainerResolutionException
[DOTNET] ---> Prism.Mvvm.ViewModelCreationException: Unable to Create ViewModel for 'myApp.Views.AppInitPage'.
[DOTNET] ---> Prism.Ioc.ContainerResolutionException: An unexpected error occurred while resolving 'myApp.ViewModels.AppInitPageViewModel'
[DOTNET] ---> DryIoc.ContainerException: code: Error.UnableToResolveFromRegisteredServices;
[DOTNET] message: Unable to resolve resolution root myApp.ViewModels.AppInitPageViewModel with passed arguments [Constant(Microsoft.Maui.Dispatching.Dispatcher, typeof(Microsoft.Maui.Dispatching.Dispatcher))]
[DOTNET] from container with scope {Name=null}
[DOTNET] with Rules with {TrackingDisposableTransients, FuncAndLazyWithoutRegistration, SelectLastRegisteredFactory} and without {ThrowOnRegisteringDisposableTransient}
[DOTNET] with FactorySelector=SelectLastRegisteredFactory
[DOTNET] with Made={FactoryMethod=ConstructorWithResolvableArguments}
[DOTNET] with normal and dynamic registrations:
[DOTNET] (DefaultDynamicKey(0), {FactoryID=869, ImplType=myApp.ViewModels.AppInitPageViewModel, Reuse=TransientReuse, HasCondition})
[DOTNET] at DryIoc.Throw.It(Int32 error, Object arg0, Object arg1, Object arg2, Object arg3) in /_/src/DryIoc/Container.cs:line 14774
[DOTNET] at DryIoc.Container.TryThrowUnableToResolve(Request request) in /_/src/DryIoc/Container.cs:line 933
[DOTNET] at DryIoc.Container.DryIoc.IContainer.ResolveFactory(Request request) in /_/src/DryIoc/Container.cs:line 915
[DOTNET] at DryIoc.Container.ResolveAndCacheKeyed(Int32 serviceTypeHash, Type serviceType, Object serviceKey, IfUnresolved ifUnresolved, Object scopeName, Type requiredServiceType, Request preResolveParent, Object[] args) in /_/src/DryIoc/Container.cs:line 510
[DOTNET] at DryIoc.Container.DryIoc.IResolver.Resolve(Type serviceType, Object serviceKey, IfUnresolved ifUnresolved, Type requiredServiceType, Request preResolveParent, Object[] args) in /_/src/DryIoc/Container.cs:line 469
[DOTNET] at DryIoc.Resolver.Resolve(IResolver resolver, Type serviceType, Object[] args, IfUnresolved ifUnresolved, Type requiredServiceType, Object serviceKey) in /_/src/DryIoc/Container.cs:line 8673
[DOTNET] at Prism.Container.DryIoc.DryIocScopedProvider.Resolve(Type type, ValueTuple`2[] parameters) in /_/src/Prism.Container.DryIoc/DryIocScopedProvider.cs:line 54
[DOTNET] --- End of inner exception stack trace ---
[DOTNET] at Prism.Container.DryIoc.DryIocScopedProvider.Resolve(Type type, ValueTuple`2[] parameters) in /_/src/Prism.Container.DryIoc/DryIocScopedProvider.cs:line 58
[DOTNET] at Prism.PrismAppBuilder.DefaultViewModelLocator(Object view, Type viewModelType) in D:\a\Prism\Prism\src\Maui\Prism.Maui\PrismAppBuilder.cs:line 118
[DOTNET] --- End of inner exception stack trace ---
[DOTNET] at Prism.PrismAppBuilder.DefaultViewModelLocator(Object view, Type viewModelType) in D:\a\Prism\Prism\src\Maui\Prism.Maui\PrismAppBuilder.cs:line 126
[DOTNET] at Prism.Mvvm.ViewModelLocationProvider.AutoWireViewModelChanged(Object view, Action`2 setDataContextCallback) in D:\a\Prism\Prism\src\Prism.Core\Mvvm\ViewModelLocationProvider.cs:line 136
[DOTNET] at Prism.Mvvm.ViewModelLocator.Autowire(Object view) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Mvvm\ViewModelLocator.cs:line 85
[DOTNET] at Prism.Mvvm.ViewRegistryBase.Autowire(BindableObject view) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Mvvm\ViewRegistryBase.cs:line 25
[DOTNET] at Prism.Mvvm.ViewRegistryBase`1[[Microsoft.Maui.Controls.BindableObject, Microsoft.Maui.Controls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].CreateView(IContainerProvider container, String name) in D:\a\Prism\Prism\src\Prism.Core\Mvvm\ViewRegistryBase{TBaseView}.cs:line 51
[DOTNET] at Prism.Navigation.PageNavigationService.CreatePage(String segmentName) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Navigation\PageNavigationService.cs:line 903
[DOTNET] --- End of inner exception stack trace ---
[DOTNET] at Prism.Navigation.PageNavigationService.CreatePage(String segmentName) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Navigation\PageNavigationService.cs:line 920
[DOTNET] at Prism.Navigation.PageNavigationService.CreatePageFromSegment(String segment) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Navigation\PageNavigationService.cs:line 943
[DOTNET] at Prism.Navigation.PageNavigationService.ProcessNavigationForRootPage(String nextSegment, Queue`1 segments, INavigationParameters parameters, Nullable`1 useModalNavigation, Nullable`1 animated) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Navigation\PageNavigationService.cs:line 589
[DOTNET] at Prism.Navigation.PageNavigationService.ProcessNavigation(Page currentPage, Queue`1 segments, INavigationParameters parameters, Nullable`1 useModalNavigation, Nullable`1 animated) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Navigation\PageNavigationService.cs:line 486
[DOTNET] at Prism.Navigation.PageNavigationService.NavigateAsync(Uri uri, INavigationParameters parameters) in D:\a\Prism\Prism\src\Maui\Prism.Maui\Navigation\PageNavigationService.cs:line 378
**Microsoft.Maui.Controls.InvalidNavigationException:** 'Expected Navigation Failed. No Root Window has been created.'
我们已经检查了 AppInitPage 上的每个依赖项，以确保它尝试使用的依赖项和服务都已构建。然后我们应该期望调用 AppInitPage 的构造函数，但是这并没有发生，因此导航不断失败。相同的 MauiProgram（除了它使用 OnAppStart 而不是 CreateWindow）在另一个应用程序中使用并且工作没有问题。
嗯，根据你的评论，作为维基答案：
这会导致导航不成功并导致 以下异常： Microsoft.Maui.Controls.InvalidNavigationException：'预期 导航失败。尚未创建根窗口。'
注册服务（monkeycache桶）可以避免这个错误。