Question

我正在创建一个需要DB的MvvmCross应用程序。我一直在关注N + 1 KittenDB示例。我不明白如何调用DataStore的初始化程序。我注意到FirstViewModel的初始化程序将它作为参数。

我运行我的代码，然后

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？

Don French

已添加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

Answer 1

针对您的具体情况：

您只需在App.cs中向Initialize添加一行，即可Register Repository类提供单IRepository个实例：

     Mvx.ConstructAndRegisterSingleton<IRepository, Repository>();

然后，MvvmCross将使用插件中的Repository创建您的ISQLiteConnectionFactory，并存储IRepository引用。

然后，这将允许MvvmCross稍后创建您的FirstViewModel

更一般的答案：

“服务建设”这个领域通常使用“控制反转”，“服务地点”和“依赖注入”等术语来引用。

MvvmCross提供了一个静态助手类Mvx，它提供了允许您Register和Resolve类和实例的机制。

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>()查找并返回已为特定界面注册的内容
IoCConstruct<MyClass>()将使用Resolve创建所请求类的实例，以填充其公共构造函数所需的任何接口引用。

插件 - 类似于SQLite-Net - 位于该层之上，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使用命名约定选择Register一个或多个批量类 - 这就是为什么您经常会在App.cs中看到一个块，如：< / p>

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

这个块只是意味着“找到名称以Service结尾的类，然后根据它们实现的接口注册它们”。请注意，此处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。

此块包含在Kittens示例中 - 其KittenGenesisService和DataService类依赖于此块进行构建 - 请参阅：

了解更多信息：

在https://github.com/slodge/MvvmCross/wiki/Service-Location-and-Inversion-of-Control
在早期的N + 1会话中引入了控制/依赖注入反转 - 请参阅http://mvvmcross.wordpress.com
（高级）平台特定的依赖注入和插件也在N = 31中进一步介绍，并且在https://github.com/slodge/MvvmCross/wiki/MvvmCross-plugins

Answer 2

一些可能被忽略的提示（他们在Stuart的例子中）：

必须初始化Sqlite插件，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。大多数情况下会提供更多信息，无法构建哪个参数。

第三：构建多个服务实例可能会在Sqlite设置的某些情况下导致错误。

希望这有助于您入门。

Answer 3

是，请仔细检查您的UI项目。您需要在核心项目中包含相同的mvvm软件包。我今天正在使用monotouch图层并收到此错误。只要我将SQLite插件添加到Touch UI，我的问题就解决了。

Answer 4

这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）

如何初始化MVvmCross SQLite插件

4 个答案: