Question

我在第一次使用SimpleIoC实例化ViewModel时遇到了以下错误。我相信我已经设置了应该是容器，但出于某种原因，我仍然得到以下错误。任何想法或帮助都将非常感激。

    Microsoft.Practices.ServiceLocation.ActivationException was unhandled by user code
  HResult=-2146233088
  Message=Type not found in cache: Windows.UI.Xaml.Controls.Frame.
  Source=GalaSoft.MvvmLight.Extras
  StackTrace:
       at GalaSoft.MvvmLight.Ioc.SimpleIoc.DoGetService(Type serviceType, String key) in c:\Users\Public\Downloads\CodePlex\MVVMLight\GalaSoft.MvvmLight\GalaSoft.MvvmLight.Extras (NET35)\Ioc\SimpleIoc.cs:line 532
       at GalaSoft.MvvmLight.Ioc.SimpleIoc.GetService(Type serviceType) in c:\Users\Public\Downloads\CodePlex\MVVMLight\GalaSoft.MvvmLight\GalaSoft.MvvmLight.Extras (NET35)\Ioc\SimpleIoc.cs:line 768
       at GalaSoft.MvvmLight.Ioc.SimpleIoc.MakeInstance[TClass]() in c:\Users\Public\Downloads\CodePlex\MVVMLight\GalaSoft.MvvmLight\GalaSoft.MvvmLight.Extras (NET35)\Ioc\SimpleIoc.cs:line 708
  InnerException:

以下是与此相关的代码：

ViewModelLocator.cs（位于我的Win8项目中）

public class ViewModelLocator
{
    /// <summary>
    /// Initializes a new instance of the ViewModelLocator class.
    /// </summary>
    public ViewModelLocator()
    {
        ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);

        if (ViewModelBase.IsInDesignModeStatic)
        {
            // Create design time view services and models
            //SimpleIoc.Default.Register<IDataService, DesignDataService>();
        }
        else
        {
            // Create run time view services and models
            //SimpleIoc.Default.Register<IDataService, DataService>();
            SimpleIoc.Default.Register<INavigationService, NavigationService>();
            SimpleIoc.Default.Register<IParseService, ParseService>();
            SimpleIoc.Default.Register<IServiceHandler, ServiceHandler>();
        }

        SimpleIoc.Default.Register<MainViewModel>();
        SimpleIoc.Default.Register<ActionViewModel>();
    }

    public MainViewModel MainVM
    {
        get
        {
            return ServiceLocator.Current.GetInstance<MainViewModel>();
        }
    }

    public ActionViewModel ActionVM
    {
        get
        {
            return ServiceLocator.Current.GetInstance<ActionViewModel>();
        }
    }

    public static void Cleanup()
    {
        // TODO Clear the ViewModels
    }
}

MainViewModel.cs构造函数

public class MainViewModel : ViewModelBase
{
    #region Variables

    private readonly INavigationService _navigationService;
    private readonly IParseService _parseService;

    #endregion

    /// <summary>
    /// Initializes a new instance of the MainViewModel class.
    /// </summary>
    public MainViewModel(INavigationService navigationService, IParseService parseService)
    {
        if (IsInDesignMode)
        {
            // Code runs in Blend --> create design time data.
        }
        else
        {
            _navigationService = navigationService;
            _parseService = parseService;
            BuildCommonData();
        }
    }

Answer 1

我知道这已经过期了，但这是我的NavigationService类实现中的违规代码。

NavigationService类（之前）

public class NavigationService : INavigationService
{
    /// <summary>
    /// Gets the root frame.
    /// </summary>
    private Frame RootFrame;

    public NavigationService(Frame rootFrame)
    {
        RootFrame = rootFrame;
    }

    public event NavigatingCancelEventHandler Navigating;

    public void Navigate<T>(object parameter = null)
    {
        var type = typeof(T);
        RootFrame.Navigate(type, parameter);
    }

    public void Navigate(string type, object parameter = null)
    {
        RootFrame.Navigate(Type.GetType(type), parameter);
    }

    public void GoBack()
    {
        if (RootFrame.CanGoBack)
        {
            RootFrame.GoBack();
        }
    }

    public void GoForward()
    {
        if (RootFrame.CanGoForward)
        {
            RootFrame.GoForward();
        }
    }
}

我只是取出了构造函数，并将RootFrame私有变量作为属性。像这样：

public class NavigationService : INavigationService
{
    /// <summary>
    /// Gets the root frame.
    /// </summary>
    private static Frame RootFrame
    {
        get { return Window.Current.Content as Frame; }
    }

    public event NavigatingCancelEventHandler Navigating;

    public void Navigate<T>(object parameter = null)
    {
        var type = typeof(T);
        RootFrame.Navigate(type, parameter);
    }

    public void Navigate(string type, object parameter = null)
    {
        RootFrame.Navigate(Type.GetType(type), parameter);
    }

    public void GoBack()
    {
        if (RootFrame.CanGoBack)
        {
            RootFrame.GoBack();
        }
    }

    public void GoForward()
    {
        if (RootFrame.CanGoForward)
        {
            RootFrame.GoForward();
        }
    }
}

简单，我知道，但希望它有一些用处。

Answer 2

今天我在Xamarin项目中遇到了同样的错误。给出的实际错误是“ System.Reflection.TargetInvocationException：'调用目标已引发异常。'”，然后当我查找InnerException时，我可以看到实际的错误。错误，这是在缓存中找不到类型。

我在构造函数依赖注入中使用DataService而不是IDataService是一个愚蠢的错误。

public SearchViewModel(DataService dataService, IErrorLoggingService errorLoggingService, IDialogService dialogService, IResourceService resourceService, INavigationService navigationService) {
    SearchCommand = new AsyncRelayCommand <SearchFilter>(SearchAsync);
    DataService = dataService;
    ErrorLoggingService = errorLoggingService;
    DialogService = dialogService;
    ResourceService = resourceService;
    NavigationService = navigationService;
    CancelCommand = new RelayCommand(Cancel);
}

仅供参考，这就是我注册服务的方式。

SimpleIoc.Default.Register<IDataService, DataService>();

因此，更改为IDataService后，此问题已解决。希望对您有所帮助。

SimpleIoC - 在缓存中找不到类型：Windows.UI.Xaml.Controls.Frame

2 个答案: