mvx：Warning：Exception masked ArgumentException：具有相同密钥的项目已被添加

Question

我试图将现有的Xamarin.Android应用程序从mvvmcross 3.5升级到mvvmcross 4.4.0。我遵循this documentation，现在应用程序构建并启动，显示启动画面，但它不会浏览启​​动画面。当我拨打ShowViewModel<MainViewModel>()时，什么都不会发生。我看到的最后一个应用程序输出是下面的输出。我目前不知道下一步要看的地方。任何人有想法？

mvx:Warning: 17,87 Exception masked ArgumentException: An item with the same key has already been added. 
     at System.ThrowHelper.ThrowArgumentException (System.ExceptionResource resource) [0x0000b] in <5d9d5f6570654147b240b9398d8953cc>:0 
    at System.Collections.Generic.Dictionary`2[TKey,TValue].Insert (TKey key, TValue value, System.Boolean add) [0x0008e] in <5d9d5f6570654147b240b9398d8953cc>:0 
    at System.Collections.Generic.Dictionary`2[TKey,TValue].Add (TKey key, TValue value) [0x00000] in <5d9d5f6570654147b240b9398d8953cc>:0 
    at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] keySelector, System.Func`2[T,TResult] elementSelector, System.Collections.Generic.IEqualityComparer`1[T] comparer) [0x0005c] in <1a5e8b31a0e44a97a3b8f85920b2d059>:0 
    at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] keySelector, System.Func`2[T,TResult] elementSelector) [0x00000] in <1a5e8b31a0e44a97a3b8f85920b2d059>:0 
    at MvvmCross.Droid.Shared.Presenter.FragmentHostRegistrationSettings.InitializeIfNeeded() [0x00128] in <90641336d9534da69c6ac9e0919ad635>:0 
    at MvvmCross.Droid.Shared.Presenter.FragmentHostRegistrationSettings.IsTypeRegisteredAsFragment (System.Type viewModelType) [0x00000] in <90641336d9534da69c6ac9e0919ad635>:0 
    at MvvmCross.Droid.Shared.Presenter.MvxFragmentsPresenter.Show (MvvmCross.Core.ViewModels.MvxViewModelRequest request) [0x0000c] in <90641336d9534da69c6ac9e0919ad635>:0 
    at MvvmCross.Droid.Views.MvxAndroidViewDispatcher+<>c__DisplayClass2_0.<ShowViewModel>b__0() [0x00000] in <f6aebf863dc84be7b380cfec8d459508>:0 
    at MvvmCross.Droid.Views.MvxAndroidMainThreadDispatcher.RequestMainThreadAction (System.Action action) [0x00019] in <f6aebf863dc84be7b380cfec8d459508>:0 
    at MvvmCross.Droid.Views.MvxAndroidViewDispatcher.ShowViewModel (MvvmCross.Core.ViewModels.MvxViewModelRequest request) [0x00014] in <f6aebf863dc84be7b380cfec8d459508>:0 
    at MvvmCross.Core.ViewModels.MvxNavigatingObject.ShowViewModelImpl (System.Type viewModelType, MvvmCross.Core.ViewModels.IMvxBundle parameterBundle, MvvmCross.Core.ViewModels.IMvxBundle presentationBundle, MvvmCross.Core.ViewModels.MvxRequestedBy requestedBy) [0x0002e] in <69bce0378e8e413982d3b552d7e387a8>:0 
    at MvvmCross.Core.ViewModels.MvxNavigatingObject.ShowViewModel (System.Type viewModelType, MvvmCross.Core.ViewModels.IMvxBundle parameterBundle, MvvmCross.Core.ViewModels.IMvxBundle presentationBundle, MvvmCross.Core.ViewModels.MvxRequestedBy requestedBy) [0x00000] in <69bce0378e8e413982d3b552d7e387a8>:0 
    at MvvmCross.Core.ViewModels.MvxNavigatingObject.ShowViewModel[TViewModel] (MvvmCross.Core.ViewModels.IMvxBundle parameterBundle, MvvmCross.Core.ViewModels.IMvxBundle presentationBundle, MvvmCross.Core.ViewModels.MvxRequestedBy requestedBy) [0x00000] in <69bce0378e8e413982d3b552d7e387a8>:0 
    at MvvmCross.Core.ViewModels.MvxAppStart`1[TViewModel].Start (System.Object hint) [0x00013] in <69bce0378e8e413982d3b552d7e387a8>:0 
    at MvvmCross.Droid.Views.MvxSplashScreenActivity.TriggerFirstNavigate() [0x00005] in <f6aebf863dc84be7b380cfec8d459508>:0 
    at MvvmCross.Droid.Views.MvxSplashScreenActivity.InitializationComplete() [0x00009] in <f6aebf863dc84be7b380cfec8d459508>:0 
    at MvvmCross.Droid.Platform.MvxAndroidSetupSingleton.<InitializeFromSplashScreen>b__7_1() [0x0000a] in <f6aebf863dc84be7b380cfec8d459508>:0 
    at MvvmCross.Platform.Core.MvxMainThreadDispatcher.ExceptionMaskedAction (System.Action action) [0x00000] in D:\git\MvvmCross\MvvmCross\Platform\Platform\Core\MvxMainThreadDispatcher.cs:22 

Answer 1

的问题是，升级到MvvmCross 4之前，我们有我们自己的执行protected override IMvxAndroidViewPresenter CreateViewPresenter()在Setup.cs。升级之后，我们改变了这种实现的（标准）实现：

protected override IMvxAndroidViewPresenter CreateViewPresenter() 
    { 
     var mvxFragmentsPresenter = new MvxFragmentsPresenter(AndroidViewAssemblies); 
     Mvx.RegisterSingleton<IMvxAndroidViewPresenter>(mvxFragmentsPresenter); 
     return mvxFragmentsPresenter; 
    } 

标准的实施不符合我们的protected override IList<Assembly> AndroidViewAssemblies执行工作逢。

解决方案：

删除assemblies.Add (typeof(...).Assembly);在protected override IList<Assembly> AndroidViewAssemblies { ... }解决我们的问题。