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我正在创建一个需要数据库的 MvvmCross 应用程序。我一直在关注 N+1 KittenDB 示例。我不明白 DataStore 的初始化程序是如何被调用的。我已经注意到 FirstViewModel 的初始化程序将其作为参数。

我运行我的代码，我得到了

Unhandled Exception:
Cirrious.CrossCore.Exceptions.MvxException: Failed to construct and initialise ViewModel for type VrWizard.Core.FirstViewModel

我的初始化程序是

private IRepository _repository;
public FirstViewModel(IRepository repository)
{
    _repository  = repository;

}

Repository 是我的 DataStore 版本：

public Repository(ISQLiteConnectionFactory factory)
{
    _connection = factory.Create ("vrwizard.sql");
    CreateTables ();
}

如何初始化存储库？

唐法语

添加了 9/23

Tis 是 Android 上错误的堆栈跟踪。我在 iPhone 上遇到同样的错误。

mvx:Diagnostic:  1.95 Creating ViewModel for ActionMain
[mvx]   2.07 Problem creating viewModel of type FirstViewModel - problem MvxException: Failed to resolve parameter for parameter factory of type ISQLiteConnectionFactory when creating VrWizard.Core.Services.DataStore.RepositoryService
[mvx]     at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.GetIoCParameterValues (System.Type type, System.Reflection.ConstructorInfo firstConstructor) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.IoCConstruct (System.Type type) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.Mvx.IocConstruct (System.Type t) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxLazySingletonCreator.get_Instance () [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxTypeExtensions+<>c__DisplayClass43.<RegisterAsLazySingleton>b__42 () [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer+ConstructingSingletonResolver.Resolve () [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.InternalTryResolve (System.Type type, ResolveOptions resolveOptions, System.Object& resolved) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.InternalTryResolve (System.Type type, System.Object& resolved) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.TryResolve (System.Type type, System.Object& resolved) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.GetIoCParameterValues (System.Type type, System.Reflection.ConstructorInfo firstConstructor) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.IoCConstruct (System.Type type) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.CrossCore.Mvx.IocConstruct (System.Type t) [0x00000] in <filename unknown>:0 
[mvx]   at Cirrious.MvvmCross.ViewModels.MvxDefaultViewModelLocator.TryLoad (System.Type viewModelType, IMvxBundle parameterValues, IMvxBundle savedState, IMvxViewModel& viewModel) [0x00000] in <filename unknown>:0 
mvx:Warning:  2.07 Problem creating viewModel of type FirstViewModel - problem MvxException: Failed to resolve parameter for parameter factory of type ISQLiteConnectionFactory when creating VrWizard.Core.Services.DataStore.RepositoryService
      at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.GetIoCParameterValues (System.Type type, System.Reflection.ConstructorInfo firstConstructor) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.IoCConstruct (System.Type type) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.Mvx.IocConstruct (System.Type t) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxLazySingletonCreator.get_Instance () [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxTypeExtensions+<>c__DisplayClass43.<RegisterAsLazySingleton>b__42 () [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer+ConstructingSingletonResolver.Resolve () [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.InternalTryResolve (System.Type type, ResolveOptions resolveOptions, System.Object& resolved) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.InternalTryResolve (System.Type type, System.Object& resolved) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.TryResolve (System.Type type, System.Object& resolved) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.GetIoCParameterValues (System.Type type, System.Reflection.ConstructorInfo firstConstructor) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.IoCConstruct (System.Type type) [0x00000] in <filename unknown>:0 
  at Cirrious.CrossCore.Mvx.IocConstruct (System.Type t) [0x00000] in <filename unknown>:0 
  at Cirrious.MvvmCross.ViewModels.MvxDefaultViewModelLocator.TryLoad (System.Type viewModelType, IMvxBundle parameterValues, IMvxBundle savedState, IMvxViewModel& viewModel) [0x00000] in <filename unknown>:0 
[MonoDroid] UNHANDLED EXCEPTION: Cirrious.CrossCore.Exceptions.MvxException: Failed to construct and initialise ViewModel for type VrWizard.Core.FirstViewModel from locator MvxDefaultViewModelLocator - check MvxTrace for more information
[MonoDroid] at Cirrious.MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest,Cirrious.MvvmCross.ViewModels.IMvxBundle,Cirrious.MvvmCross.ViewModels.IMvxViewModelLocator) <0x00148>
[MonoDroid] at Cirrious.MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest,Cirrious.MvvmCross.ViewModels.IMvxBundle) <0x0006b>
[MonoDroid] at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewsContainer.DirectLoad (Cirrious.MvvmCross.ViewModels.IMvxBundle,System.Type) <0x0008b>
[MonoDroid] at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewsContainer.Load (Android.Content.Intent,Cirrious.MvvmCross.ViewModels.IMvxBundle,System.Type) <0x000ab>
[MonoDroid] at Cirrious.MvvmCross.Droid.Views.MvxActivityViewExtensions.LoadViewModel (Cirrious.MvvmCross.Droid.Views.IMvxAndroidView,Cirrious.MvvmCross.ViewModels.IMvxBundle) <0x00137>
[MonoDroid] at Cirrious.MvvmCross.Droid.Views.MvxActivityViewExtensions/<>c__DisplayClass3.<OnViewCreate>b__1 () <0x00027>
[MonoDroid] at Cirrious.MvvmCross.Views.MvxViewExtensionMethods.OnViewCreate (Cirrious.MvvmCross.Views.IMvxView,System.Func`1<Cirrious.MvvmCross.ViewModels.IMvxViewModel>) <0x00053>
[MonoDroid] at Cirrious.MvvmCross.Droid.Views.MvxActivityViewExtensions.OnViewCreate (Cirrious.MvvmCross.Droid.Views.IMvxAndroidView,Android.OS.Bundle) <0x001d7>
[MonoDroid] at Cirrious.MvvmCross.Droid.Views.MvxActivityAdapter.EventSourceOnCreateCalled (object,Cirrious.CrossCore.Core.MvxValueEventArgs`1<Android.OS.Bundle>) <0x000f7>
[MonoDroid] at (wrapper delegate-invoke) System.EventHandler`1<Cirrious.CrossCore.Core.MvxValueEventArgs`1<Android.OS.Bundle>>.invoke_void__this___object_TEventArgs (object,Cirrious.CrossCore.Core.MvxValueEventArgs`1<Android.OS.Bundle>) <0x000ab>
[MonoDroid] at Cirrious.CrossCore.Droid.Views.MvxDelegateExtensionMethods.Raise<Android.OS.Bundle> (System.EventHandler`1<Cirrious.CrossCore.Core.MvxValueEventArgs`1<Android.OS.Bundle>>,object,Android.OS.Bundle) <0x0004b>
[MonoDroid] at Cirrious.CrossCore.Droid.Views.MvxEventSourceActivity.OnCreate (Android.OS.Bundle) <0x00033>
[MonoDroid] at VrWizard.Droid.FirstView.OnCreate (Android.OS.Bundle) <0x0001b>
[MonoDroid] at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (intptr,intptr,intptr) <0x0005b>
[MonoDroid] at (wrapper dynamic-method) object.23d26989-db28-4670-bfbb-658531972ead (intptr,intptr,intptr) <0x00043>
[mono] 
[mono] Unhandled Exception:
[mono] Cirrious.CrossCore.Exceptions.MvxException: Failed to construct and initialise ViewModel for type VrWizard.Core.FirstViewModel from locator MvxDefaultViewModelLocator - check MvxTrace for more information
[mono]   at Cirrious.MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest request, IMvxBundle savedState, IMvxViewModelLocator viewModelLocator) [0x00000] in <filename unknown>:0 
[mono]   at Cirrious.MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest request, IMvxBundle savedState) [0x00000] in <filename unknown>:0 
[mono]   at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewsContainer.DirectLoad (IMvxBundle savedState, System.Type viewModelTypeHint) [0x00000] in <filename unknown>:0 
[mono]   at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewsContainer.Load (Android.Content.Intent intent, IMvxBundle savedState, System.Type viewModelTypeHint) [0x00000] in <filename unknown>:0 
[mono]   at Cirrious.MvvmCross.Droid.Views.
[mono-rt] [ERROR] FATAL UNHANDLED EXCEPTION: Cirrious.CrossCore.Exceptions.MvxException: Failed to construct and initialise ViewModel for type VrWizard.Core.FirstViewModel from locator MvxDefaultViewModelLocator - check MvxTrace for more information
[mono-rt]   at Cirrious.MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest request, IMvxBundle savedState, IMvxViewModelLocator viewModelLocator) [0x00000] in <filename unknown>:0 
[mono-rt]   at Cirrious.MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest request, IMvxBundle savedState) [0x00000] in <filename unknown>:0 
[mono-rt]   at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewsContainer.DirectLoad (IMvxBundle savedState, System.Type viewModelTypeHint) [0x00000] in <filename unknown>:0 
[mono-rt]   at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewsContainer.Load (Android.Content.Intent intent, IMvxBundle savedState, System.Type viewModelTypeHint) [0x00000] in <filename unknown>:0 
[mono-rt]   at Cirrious.MvvmCross
4

4 回答 4

6

对于您的具体情况：

您可以简单地Initialize在 App.cs 中添加一行，以允许您将Register类Repository作为提供单例IRepository实例：

     Mvx.ConstructAndRegisterSingleton<IRepository, Repository>();

然后 MvvmCross 将Repository使用ISQLiteConnectionFactory插件中的 an 创建您的，并将存储该IRepository引用。

这将允许 MvvmCross 稍后创建您的FirstViewModel

对于更一般的答案：

这个“服务构建”领域通常使用“控制反转”、“服务位置”和“依赖注入”等术语来指代。

MvvmCross 提供了一个静态帮助类Mvx，它提供了允许您访问类Register和Resolve实例的机制。

这些机制包括：

  • RegisterSingleton<IMyInterface>(new MyThing())它允许您将类的实例注册为将实现特定接口的唯一事物。
  • Resolve<IMyInterface>()它查找并返回已为特定接口注册的内容
  • IoCConstruct<MyClass>()它将创建所请求类的实例，Resolve用于填充其公共构造函数所需的任何接口引用。

插件（如 SQLite-Net）位于这一层之上，并使用Register机制使服务可供应用程序代码使用。

另一个常用选项是您的应用程序代码也可以Register使用命名约定选择一个或多个批量类集 - 这就是为什么您经常会在 App.cs 中看到一个块，例如：

    CreatableTypes()
        .EndingWith("Service")
        .AsInterfaces()
        .RegisterAsLazySingleton();

这个块简单的意思是“找到名称以 结尾的类，Service然后根据它们实现的接口注册它们”。请注意，这Service只是一个后缀词 - 您可以通过更改EndingWith行轻松使用不同的命名约定。

这个块包含在 Kittens 示例中 - 它KittenGenesisService和DataService类都依赖于这个块来构建它们 - 请参阅：

了解更多信息：

于 2013-09-22T17:25:54.793 回答
3

一些可能被忽略的提示（它们在 Stuart 的示例中）：

  • 必须初始化 Sqlite 插件的某个地方，查找引导类。

    使用 Cirrious.CrossCore.Plugins；

    namespace myapp.UI.Android.Bootstrap
{
    public class SqlitePluginBootstrap
        : MvxPluginBootstrapAction<Cirrious.MvvmCross.Plugins.Sqlite.PluginLoader>
    {
    }
}

其次，更彻底地检查错误。大多数时候提供了更多信息，无法构造哪个参数。

第三：在 Sqlite 设置的某些情况下，构建服务的多个实例可能会导致错误。

希望这可以帮助您入门。

于 2013-09-23T14:32:42.057 回答
2

是的，请仔细检查您的 UI 项目。您需要在其中包含与核心项目中相同的 mvvm 包。我今天正在使用单触图层并收到此错误。一旦我将 SQLite 插件添加到 Touch UI，我的问题就解决了。

于 2014-10-15T13:14:12.903 回答
0

那只是因为你没有在包含视图的项目中添加 SQLite 的 NuGet 包，（意味着 Windows Phone 8 项目）

于 2014-06-11T09:11:13.483 回答