MvvmCross綁定到InteractionRequest

Question

我試圖在iOS中使用mvvmcross實現模式確認彈出窗口，其後跟着斯圖爾特的大綱this question。我得到試圖將InteractionRequest綁定到事件處理程序時出現以下異常：

Problem seen during binding execution for to ConfirmationInteraction - problem 
TargetInvocationException: Exception has been thrown by the target of an invocation. 

內部異常是：

ArgumentNullException: missing source event info in MvxWeakEventSubscription 
Parameter name: sourceEventInfo 
at Cirrious.CrossCore.WeakSubscription.MvxWeakEventSubscription`2[System.Object,System.EventArgs]..ctor (System.Object source, System.Reflection.EventInfo sourceEventInfo, System.EventHandler`1 targetEventHandler) [0x00000] in <filename unknown>:0 
at Cirrious.CrossCore.WeakSubscription.MvxGeneralEventSubscription..ctor (System.Object source, System.Reflection.EventInfo eventInfo, System.EventHandler`1 eventHandler) [0x00000] in <filename unknown>:0 
at Cirrious.CrossCore.WeakSubscription.MvxWeakSubscriptionExtensionMethods.WeakSubscribe (System.Reflection.EventInfo eventInfo, System.Object source, System.EventHandler`1 eventHandler) [0x00000] in <filename unknown>:0 

大部分管道的是與上面所引用的堆棧溢出的問題，但我將它張貼在這裏的完整性：

public class InteractionRequestedEventArgs : EventArgs 
{ 
    public Action Callback 
    { 
     get; 
     private set; 
    } 

    public object Context 
    { 
     get; 
     private set; 
    } 

    public InteractionRequestedEventArgs(object context, Action callback) 
    { 
     Context = context; 
     Callback = callback; 
    } 
} 

的InteractionRequest：

public class InteractionRequest<T> : IInteractionRequest 
{ 
    public event EventHandler<InteractionRequestedEventArgs> Raised; 

    public void Raise(T context, Action<T> callback) 
    { 
     var handler = this.Raised; 
     if (handler != null) 
     { 
      handler(
       this, 
       new InteractionRequestedEventArgs(
       context, 
       () => callback(context))); 
     } 
    } 
} 

確認類：

public class Confirmation 
{ 
    public string Message { get; private set; } 
    public bool Confirmed { get; set; } 
    public Confirmation(string message) 
    { 
     Message = message; 
    } 
} 

在視圖模型中，我們設置爲這樣的要求：在視圖

private InteractionRequest<Confirmation> _confirmCancelInteractionRequest = new InteractionRequest<Confirmation>(); 
    public IInteractionRequest ConfirmCancelInteractionRequest 
    { 
     get 
     { 
      return _confirmCancelInteractionRequest; 
     } 
    } 

我們成立了事件訂閱：

private MvxGeneralEventSubscription _confirmationSubscription; 
    private IInteractionRequest _confirmationInteraction; 
    public IInteractionRequest ConfirmationInteraction 
    { 
     get { 
      return _confirmationInteraction; 
     } 
     set 
     { 
      if (_confirmationInteraction == value) 
       return; 
      if (_confirmationSubscription != null) 
       _confirmationSubscription.Dispose(); 
      _confirmationInteraction = value; 
      if (_confirmationInteraction != null) 
       _confirmationSubscription = _confirmationInteraction 
        .GetType() 
        .GetEvent ("Raise") 
        .WeakSubscribe(_confirmationInteraction, DoConfirmation); 

     } 
    } 

視圖中的事件處理程序如下所示：

private void DoConfirmation(object s, EventArgs args) 
    { 
     var iArgs = (InteractionRequestedEventArgs)args; 
     var confirmation = (Confirmation)iArgs.Context; 

     var alert = new UIAlertView(); 
     alert.Title = "Bazinga"; 
     alert.Message = confirmation.Message; 

     alert.AddButton("Yes"); 
     alert.AddButton("No"); 

     alert.Clicked += (sender, e) => { 
      var alertView = sender as UIAlertView; 
          // do something with the event 
      iArgs.Callback(); 
     }; 
    } 

最後是綁定，它在視圖的構造函數中。該視圖是一個MT對話框元素，因此DelayBind（）：

this.DelayBind(() => 
     { 
      var set = this.CreateBindingSet<CustomerElement, CustomerViewModel>(); 
      ... 
      set.Bind().For(my => my.ConfirmationInteraction).To(customer => customer.ConfirmCancelInteractionRequest); 
      set.Apply(); 
     }); 
    } 

Answer 1

與堆疊的空引用異常

at Cirrious.CrossCore.WeakSubscription.MvxWeakEventSubscription`2[System.Object,System.EventArgs]..ctor (System.Object source, System.Reflection.EventInfo sourceEventInfo, System.EventHandler`1 targetEventHandler) [0x00000] in <filename unknown>:0 
at Cirrious.CrossCore.WeakSubscription.MvxGeneralEventSubscription..ctor (System.Object source, System.Reflection.EventInfo eventInfo, System.EventHandler`1 eventHandler) [0x00000] in <filename unknown>:0 
at Cirrious.CrossCore.WeakSubscription.MvxWeakSubscriptionExtensionMethods.WeakSubscribe (System.Reflection.EventInfo eventInfo, System.Object source, System.EventHandler`1 eventHandler) [0x00000] in <filename unknown>:0 

只能出現如果_confirmationInteraction.GetType().GetEvent ("Raise")返回null

所以...我認爲問題可能是您的活動被稱爲Raised

---

如果有幫助：

• 的3.0.13版本MvvmCross的包括了互動一些初步的助手 - 例如看到https://github.com/MvvmCross/MvvmCross/blob/v3/Cirrious/Cirrious.MvvmCross/ViewModels/MvxInteraction.cs - 我希望並期待，我們將建立在這個在未來版本
• 爲簡單的「消息框」互動@BrianChance提供該工廠插件 - https://github.com/brianchance/MvvmCross-UserInteraction