Question

我正在使用MVVM light toolkit的Messenger类来传达我的WP7应用程序的不同部分。

我正在尝试从我的应用程序类接收消息时使视图转到不同的状态。在视图的代码隐藏中，我注册了消息：

Messenger.Default.Register<PageActionMessage>
(
     this,
    (action) => GoToPage(action)
);

并在收到时调用以下方法：

private object GoToPage(PageActionMessage action)
{
    if (action.action == PageAction.TwitterAuthFinished)
    {
        if (IsoStoreHelper.CheckIfAuthorized())
        {
            VisualStateManager.GoToState(this, "TwitterSendPage", true); // The exception is thrown here
        }
     }
}

在我的另一堂课中，信息以这种方式播放：

var PageMsg = new PageActionMessage()
{
    action = PageAction.TwitterAuthFinished
};
Messenger.Default.Send<PageActionMessage>(PageMsg);

视图正确接收此消息，但在调用VisualStateManager的GoToState方法时，将抛出UnauthorizedAccessException（无效的跨线程访问），并带有以下跟踪：

System.UnauthorizedAccessException was unhandled
  Message=Invalid cross-thread access.
 StackTrace:
   at MS.Internal.XcpImports.CheckThread()
   at System.Windows.DependencyObject.GetValueInternal(DependencyProperty dp)
   at System.Windows.FrameworkElement.GetValueInternal(DependencyProperty dp)
   at System.Windows.DependencyObject.GetValue(DependencyProperty dp)
   at System.Windows.Controls.Panel.get_Children()
   at MS.Internal.XcpImports.CheckThread()
   at MS.Internal.XcpImports.Control_GetImplementationRoot(Control control)
   at System.Windows.Controls.Control.get_ImplementationRoot()
   at System.Windows.VisualStateManager.GoToState(Control control, String stateName, Boolean useTransitions)
   at KidsBook.MainPage.GoToPage(PageActionMessage action)
   at KidsBook.MainPage.<.ctor>b__0(PageActionMessage action)
   at GalaSoft.MvvmLight.Helpers.WeakAction`1.Execute(PageActionMessage parameter)
   at GalaSoft.MvvmLight.Helpers.WeakAction`1.ExecuteWithObject(Object parameter)
   at GalaSoft.MvvmLight.Messaging.Messenger.SendToList[TMessage](PageActionMessage message, IEnumerable`1 list, Type messageTargetType, Object token)
   at GalaSoft.MvvmLight.Messaging.Messenger.SendToTargetOrType[TMessage](PageActionMessage message, Type messageTargetType, Object token)
   at GalaSoft.MvvmLight.Messaging.Messenger.Send[TMessage](PageActionMessage message)
   at KidsBook.Twitter.OAuthClient.GetResponse(IAsyncResult result)
   at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClassa.<InvokeGetResponseCallback>b__8(Object state2)
   at System.Threading.ThreadPool.WorkItem.WaitCallback_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadPool.WorkItem.doWork(Object o)
   at System.Threading.Timer.ring()

这到底是什么原因？提前谢谢！

Answer 1

使用MVVVMLight，您可以使用DispatcherHelper来确保代码在UI线程上运行（您的问题）。
e.g。

DispatcherHelper.CheckBeginInvokeOnUI(YOUR-ACTION);

Answer 2

这是我的解决方案：

http://wp8xp.blogspot.com.es/2013/02/llamadas-asincronas-internet-haciendo.html

Deployment.Current.Dispatcher.BeginInvoke(() =>
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            });

使用MVVM Light在WP7项目中抛出UnauthorizedAccessException（无效的跨线程访问）

2 个答案: