加載ReactiveUI執行命令

Question

我想實現一個視圖/視圖模型，當應用程序檢查用戶是否通過身份驗證時將顯示該視圖/視圖模型。

下面的代碼以多次調用路由器結束。 InternalIsAuthenticated中的測試代碼有問題嗎？我怎樣才能實現這個正確的？

視圖模型：

public class LoadingViewModel : ReactiveObject, IRoutableViewModel 
    { 
     public string UrlPathSegment { 
      get { 
       return "Loading"; 
      } 
     } 

     public IScreen HostScreen { get; protected set; } 

     public ReactiveCommand<bool> IsAuthenticatedCommand { get; protected set; } 

     public LoadingViewModel (IScreen screen) 
     { 
      HostScreen = screen; 
      IsAuthenticatedCommand = ReactiveCommand.CreateAsyncTask (async (_, ctx) => await InternalIsAuthenticated()); 
      IsAuthenticatedCommand.Subscribe(next => { 
       //called twice. ?? 
       HostScreen.Router.NavigateAndReset.Execute(new OnboardingViewModel(HostScreen)); 
      }); 
      IsAuthenticatedCommand.ThrownExceptions.Subscribe(ex => { 
       Debug.WriteLine(ex.Message); 
       UserError.Throw("oops"); 
      }); 

      //Error: nested push animation can result in corrupted navigation bar 
      //Error: Finishing up a navigation transition in an unexpected state. Navigation Bar subview tree might get corrupted. 
      //this.WhenAnyValue(x => x.UrlPathSegment) 
      // .Throttle(TimeSpan.FromSeconds(1), RxApp.MainThreadScheduler) 
      // .InvokeCommand(this, x => x.IsAuthenticatedCommand); 

      //Error: nested push animation can result in corrupted navigation bar 
      //Error: Finishing up a navigation transition in an unexpected state. Navigation Bar subview tree might get corrupted. 
      this.IsAuthenticatedCommand.ExecuteAsyncTask(); 

      //OnboardingView ends on top of LoadingView in the navigation stack. 
      //HostScreen.Router.NavigateAndReset.Execute(new OnboardingViewModel(HostScreen)); 
     } 

     private async Task<bool> InternalIsAuthenticated(){ 
      return await Task.Run(() => {return true;}); 
     } 
    } 

查看：

public partial class LoadingView : ContentPage, IViewFor<LoadingViewModel> 
    { 
     public LoadingView() 
     { 
      InitializeComponent(); 
      this.WhenAnyValue (x => x.ViewModel).BindTo (this, x => x.BindingContext); 
     } 

     public LoadingViewModel ViewModel { 
      get { return (LoadingViewModel)GetValue(ViewModelProperty); } 
      set { SetValue(ViewModelProperty, value); } 
     } 
     public static readonly BindableProperty ViewModelProperty = 
      BindableProperty.Create<LoadingView, LoadingViewModel>(x => x.ViewModel, default(LoadingViewModel), BindingMode.OneWay); 

     object IViewFor.ViewModel { 
      get { return ViewModel; } 
      set { ViewModel = (LoadingViewModel)value; } 
     } 
    } 

Answer 1

如果NavigateAndReset獲取調用兩次，也許是因爲你創建兩個LoadingViewModels？