舊的ViewModel被重用，而不是構建新的視圖

Question

有時，當活動被破壞（不知道爲什麼，我假設的內存壓力）時，會創建一個新活動，但綁定到活動活動的舊視圖模型會被重用。

活動：

[Activity( 
    LaunchMode = LaunchMode.SingleTask, 
    ConfigurationChanges = ConfigChanges.Orientation | ConfigChanges.ScreenSize)] 
public class HomeView : MvxTabsFragmentActivity 
{ 
    protected override void OnCreate(Bundle bundle) 
    { 
     Log.Info("On HomeView created"); 
     base.OnCreate(bundle); 
    } 

    protected override void OnDestroy() 
    { 
     base.OnDestroy(); 
     Log.Info("On HomeView destroyed"); 
     this.HomeViewModel.CleanUp(); 
    }   
} 

視圖模型：

public class HomeViewModel : MvxViewModel 
{ 
    public HomeViewModel(
     IMvxMessenger messenger, 
     IUserInteraction userInteraction, 
     DashboardViewModel dashboardViewModel, 
     AlertSettingsViewModel alertSettingsViewModel) 
    { 
     Log.Info("Building home view model"); 
    } 

    public void CleanUp() 
    { 
     Log.Info("HomeViewModel => Clean-up"); 
    }  
} 

App.cs：

public override void Initialize() 
    { 
     this.CreatableTypes().EndingWith("ViewModel").AsTypes().RegisterAsDynamic(); 

     this.RegisterAppStart<HomeViewModel>(); 

     TaskScheduler.UnobservedTaskException += 
      (sender, eventArgs) => 
      Log.Error("An Unobserved exception has been raised by a task", eventArgs.Exception); 
    } 

調試輸出：

On HomeView created 
Building home view model 
... 
On HomeView destroyed 
HomeViewModel => Clean-up 
... 
On HomeView created 
[here: no "Building view model" message] 

也許這是SingleTask活動？

有沒有一種方法（與IoC或其他）在每個HomeView創建中獲得全新視圖模型？

編輯：

我跑過去對MvxActivityViewExtensions.cs

public static void OnViewCreate(this IMvxAndroidView androidView, Bundle bundle) 
{ 
    MvxActivityViewExtensions.EnsureSetupInitialized(androidView); 
    MvxActivityViewExtensions.OnLifetimeEvent(androidView, (Action<IMvxAndroidActivityLifetimeListener, Activity>) ((listener, activity) => listener.OnCreate(activity))); 
    IMvxViewModel cached = Mvx.Resolve<IMvxSingleViewModelCache>().GetAndClear(bundle); 
    IMvxView view = (IMvxView) androidView; 
    IMvxBundle savedState = MvxActivityViewExtensions.GetSavedStateFromBundle(bundle); 
    MvxViewExtensionMethods.OnViewCreate(view, (Func<IMvxViewModel>) (() => cached ?? MvxActivityViewExtensions.LoadViewModel(androidView, savedState))); 
} 

此方法，以便將它意味着我的視圖模型被緩存？如何禁用此緩存？

Answer 1

這是覆蓋在Wiki中https://github.com/MvvmCross/MvvmCross/wiki/Customising-using-App-and-Setup#overriding-viewmodel-locationconstruction

---

默認情況下，MvvmCross構建一個新的視圖模型每次請求一個時間和使用CIRS序列 - 建築 - INIT-ReloadState啓動 - 初始化該視圖模型。

如果您想爲一個或多個ViewModel類型覆蓋此行爲，那麼您可以通過提供您自己的IMvxViewModelLocator實現在App對象中執行此操作。

例如，你可以實現

public class MyViewModelLocator 
    : MvxDefaultViewModelLocator 
{ 
    private SpecialViewModel _special = new SpecialViewModel(); 

    public override bool TryLoad(Type viewModelType, IDictionary<string, string> parameterValueLookup, 
           out IMvxViewModel model) 
    { 
     if (viewModelType == typeof(SpecialViewModel)) 
     { 
      model = _special; 
      return true; 
     } 
     else if (viewModelType == typeof(FooViewModel)) 
     { 
      model = new FooViewModel(_special); 
      return true; 
     } 

     return base.TryLoad(viewModelType, parameterValueLookup, out model); 
    } 
} 

，然後可以在App.cs返回此：

protected override IMvxViewModelLocator CreateDefaultViewModelLocator() 
{ 
    return new MyViewModelLocator(); 
}