Question

我正在尝试使用ViewModelLocator（Microsoft提供的一种）将视图绑定到ViewModels，该方法使用自定义AppContainer类来解析动态获取的ViewModel的modelType。但是，每当调用此Resolve函数时，它都会引发“ Autofac.Core.DependencyResolutionException”。

完整错误：

Autofac.Core.DependencyResolutionException Message =激活Kahood3.ViewModels.LandingsPageViewModel-> Kahood3.Services.NavigationService时引发异常。来源= Autofac 堆栈跟踪：在C：\ projects \ autofac \ src \ Autofac \ Core \ Lifetime \ LifetimeScope中的Autofac.Core.Resolving.InstanceLookup.Activate（System.Collections.Generic.IEnumerable 1[T] parameters, System.Object& decoratorTarget) [0x00060] in C:\projects\autofac\src\Autofac\Core\Resolving\InstanceLookup.cs:135 at Autofac.Core.Resolving.InstanceLookup+<>c__DisplayClass6_0.<Execute>b__0 () [0x00000] in C:\projects\autofac\src\Autofac\Core\Resolving\InstanceLookup.cs:85 at Autofac.Core.Lifetime.LifetimeScope.GetOrCreateAndShare (System.Guid id, System.Func 1 [TResult]创建者）[0x00045]处。 cs：312 在C：\ projects \ autofac \ src \ Autofac \ Core \ Resolving \ InstanceLookup.cs：83中的Autofac.Core.Resolving.InstanceLookup.Execute（）[0x0003e] 在C：\中位于Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance（Autofac.Core.ISharingLifetimeScope currentOperationScope，Autofac.Core.IComponentRegistration注册，System.Collections.Generic.IEnumerable 1[T] parameters) [0x00071] in C:\projects\autofac\src\Autofac\Core\Resolving\ResolveOperation.cs:131 at Autofac.Core.Resolving.ResolveOperation.ResolveComponent (Autofac.Core.IComponentRegistration registration, System.Collections.Generic.IEnumerable 1 [T]参数）[0x00000]处projects \ autofac \ src \ Autofac \ Core \ Resolveving \ ResolveOperation.cs：69 在C：\ projects \ autofac \ src \ Autofac中的Autofac.Core.Resolving.ResolveOperation.Execute（Autofac.Core.IComponentRegistration注册，System.Collections.Generic.IEnumerable 1[T] parameters) [0x00016] in C:\projects\autofac\src\Autofac\Core\Resolving\ResolveOperation.cs:93 at Autofac.Core.Lifetime.LifetimeScope.ResolveComponent (Autofac.Core.IComponentRegistration registration, System.Collections.Generic.IEnumerable 1 [T]参数）[0x00041] \ Core \ Lifetime \ LifetimeScope.cs：282 在C：\ projects \ autofac \中的Autofac.Core.Container.ResolveComponent（Autofac.Core.IComponentRegistration注册，System.Collections.Generic.IEnumerable 1[T] parameters) [0x00000] in C:\projects\autofac\src\Autofac\Core\Container.cs:170 at Autofac.ResolutionExtensions.TryResolveService (Autofac.IComponentContext context, Autofac.Core.Service service, System.Collections.Generic.IEnumerable 1 [T]参数，System.Object和实例）中[0x00023] src \ Autofac \ ResolutionExtensions.cs：1041 在C：\ projects \ autofac \ src \下的Autofac.ResolutionExtensions.ResolveService（Autofac.IComponentContext上下文，Autofac.Core.Service服务，System.Collections.Generic.IEnumerable 1[T] parameters) [0x00030] in C:\projects\autofac\src\Autofac\ResolutionExtensions.cs:877 at Autofac.ResolutionExtensions.Resolve (Autofac.IComponentContext context, System.Type serviceType, System.Collections.Generic.IEnumerable 1 [T]参数）[0x00000]中Autofac \ ResolutionExtensions.cs：347 在C：\ projects \ autofac \ src \ Autofac \ ResolutionExtensions.cs：331中的Autofac.ResolutionExtensions.Resolve（Autofac.IComponentContext上下文，System.Type serviceType）[0x00000]中在C：... \ Kahood3 \ Kahood3 \ Kahood3 \ Util \ AppContainer.cs：29中的Kahood3.Util.AppContainer.Resolve（System.Type typeName）[0x00001]中在C：... \ Util \ ViewModelLocator.cs：56中位于Kahood3.Util.ViewModelLocator.OnAutoWireViewModelChanged（Xamarin.Forms.BindableObject可绑定，System.Object oldValue，System.Object newValue）[0x000b8] 在Xamarin.Forms.BindableObject.SetValueActual处（Xamarin.Forms.BindableProperty属性，Xamarin.Forms.BindableObject + BindablePropertyContext上下文，System.Object值，System.Boolean当前应用，Xamarin.Forms.Internals.SetValueFlags属性，System.Boolean无提示）[ 0x00120]在D：\ a \ 1 \ s \ Xamarin.Forms.Core \ BindableObject.cs：445中位于Da：\ a \ 1 \中的Xamarin.Forms.BindableObject.SetValueCore（Xamarin.Forms.BindableProperty属性，System.Object值，Xamarin.Forms.Internals.SetValueFlags属性，Xamarin.Forms.BindableObject + SetValuePrivateFlags privateAttributes）[0x00173] s \ Xamarin.Forms.Core \ BindableObject.cs：379 位于D：\ a \ 1 \ s \ Xamarin.Forms.Core \中的Xamarin.Forms.BindableObject.SetValue（Xamarin.Forms.BindableProperty属性，System.Object值，System.Boolean fromStyle，System.Boolean checkAccess）[0x00042] BindableObject.cs：316 位于Da：\ a \ 1 \ s \ Xamarin.Forms.Core \ BindableObject.cs：293中的Xamarin.Forms.BindableObject.SetValue（Xamarin.Forms.BindableProperty属性，System.Object值）[0x00000] 在Kahood3.Views.LandingsPageView.InitializeComponent（）[0x00023]在C：\ Users ... \ obj \ Debug \ netstandard2.0 \ Views \ LandingsPageView.xaml.g.cs：26中在Kahood3.Views.LandingsPageView..ctor（）[0x00008]在C：\ Users ... \ Views \ LandingsPageView.xaml.cs：20中在C：\ Users ... \ App.xaml.cs：19中的Kahood3.App..ctor（）[0x0001d]中在C：\ Users ... \ Kahood3.Android \ MainActivity.cs：24中的Kahood3.Droid.MainActivity.OnCreate（Android.OS.Bundle savedInstanceState）[0x0002f]中在Android.App.Activity.n_OnCreate_Landroid_os_Bundle_（System.IntPtr jnienv，System.IntPtr native__this，System.IntPtr native_savedInstanceState）中：[0x00011]，位于：0 在（包装器动态方法）Android.Runtime.DynamicMethodNameCounter.8（intptr，intptr，intptr）

我尝试调试不同的变量，但没有任何进展。在检查viewModelType的值时，它会显示正确的ViewModel。

ViewModelLocator文件

private static void OnAutoWireViewModelChanged(BindableObject bindable, object oldValue, object newValue)
{
    System.Diagnostics.Debug.Write("Inside OnAutoWireViewModelChanged");

    if (!(bindable is Element view))
    {
        return;
    }

    var viewType = view.GetType();
    if (viewType.FullName != null)
    {
        var viewName = viewType.FullName.Replace(".Views.", ".ViewModels.");
        var viewAssemblyName = viewType.GetTypeInfo().Assembly.FullName;
        var viewModelName = string.Format(CultureInfo.InvariantCulture, "{0}Model, {1}", viewName, viewAssemblyName);
        //var viewModelName = string.Format(CultureInfo.InvariantCulture, "{0}Model", viewName);

        System.Diagnostics.Debug.Write(" viewModelName: " + viewModelName);
        System.Diagnostics.Debug.Write(" viewAssemblyName: " + viewAssemblyName);

        var viewModelType = Type.GetType(viewModelName);
        if (viewModelType == null)
        {
            return;
        }
        var viewModel = AppContainer.Resolve(viewModelType); //Resolve the viewModelType
        view.BindingContext = viewModel;
    }
}

在AppContainer内

public static object Resolve(Type typeName)
{
    return _container.Resolve(typeName); //Throws the error here
}

查看XAML文件：

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         xmlns:d="http://xamarin.com/schemas/2014/forms/design"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
         xmlns:local="clr-namespace:Kahood3.ViewModels"
         mc:Ignorable="d"
         x:Class="Kahood3.Views.LandingsPageView"
         xmlns:utility="clr-namespace:Kahood3.Util"
         utility:ViewModelLocator.AutoWireViewModel="True">


    <StackLayout>
        <Label Text="{Binding Title}"
           FontSize="Large"
           HorizontalOptions="Center"
           VerticalOptions="Center">
        </Label>
        <Button x:Name="startButton" Text="Start!" Command="{Binding Source={x:Reference startButton}, Path=BindingContext.Start_Quiz}" CommandParameter="{Binding}"/>
    </StackLayout>

</ContentPage>

在AppContainer中解析viewModelType时发生Autofac.Core.DependencyResolutionException

0 个答案: