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社区首页 >问答首页 >如何初始化theMvvmCross SQLite插件

问如何初始化theMvvmCross SQLite插件
EN

Stack Overflow用户
提问于 2013-09-22 05:52:01
回答 3查看 4K关注 0票数 0

我正在创建一个需要DB的MvvmCross应用程序。我一直在学习N+1 KittenDB的例子。我不明白DataStore的初始化程序是如何被调用的。我注意到FirstViewModel的初始化器将它作为参数。

我运行我的代码

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

我的初始化器是

代码语言：javascript
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private IRepository _repository;
public FirstViewModel(IRepository repository)
{
    _repository  = repository;

}

存储库是我的DataStore版本：

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

如何初始化存储库？

法国唐

增加9/23

它是Android上错误的堆栈跟踪。我在iPhone上也有同样的错误。

代码语言：javascript
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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
xamarin
mvvmcross
EN

回答 3

Stack Overflow用户

回答已采纳

发布于 2013-09-22 17:25:54

就你的具体情况而言：

您只需在Initialize中添加一行App.cs，就可以将Repository类作为提供单例IRepository实例的Register：

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     Mvx.ConstructAndRegisterSingleton<IRepository, Repository>();

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

这将允许MvvmCross稍后创建您的FirstViewModel

关于更一般的答案：

“服务构建”的这一领域经常使用“控制反转”、“服务位置”和“依赖注入”等术语。

MvvmCross提供了一个静态帮助类Mvx，它提供了允许您使用Register和Resolve类和实例的机制。

这些机制包括：

  • RegisterSingleton<IMyInterface>(new MyThing())允许您将类的实例注册为实现特定接口的惟一对象。
  • Resolve<IMyInterface>()，它查找并返回已为特定接口注册的内容
  • IoCConstruct<MyClass>()，它将使用Resolve创建被请求类的实例，以填充其公共构造函数所需的任何接口引用。

插件--比如SQLite-Net --位于这一层的顶部，并使用Register机制使应用程序代码可以使用服务。

另一个常用的选项是，应用程序代码还可以使用命名约定选择Register一个或多个类的大集合--这就是为什么在App.cs中经常会看到如下所示的块：

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

这个块的意思只是“查找以Service结尾的类，然后根据它们实现的接口注册它们”。注意，Service只是一个后缀词--通过更改EndingWith行，您可以很容易地使用不同的命名约定。

这个块包含在Kitten示例中--它的KittenGenesisService和DataService类依赖于这个块来构建它们--请参见：

有关详细信息，请参阅：

票数 6
EN

Stack Overflow用户

发布于 2013-09-23 14:32:42

一些可能被忽略的小技巧(在斯图尔特的例子中就是如此)：

  • 在某个地方，Sqlite必须初始化，寻找引导类。 使用Cirrious.CrossCore.Plugins； 命名空间myapp.UI.Android.Bootstrap {公共类SqlitePluginBootstrap :myapp.UI.Android.Bootstrap{}

第二，更彻底地检查错误。大多数情况下，提供了更多的信息，哪些参数无法构造。

第三，构建服务的多个实例可能会导致在Sqlite设置的某些情况下出现错误。

希望这能帮助你开始工作。

票数 3
EN

Stack Overflow用户

发布于 2014-06-11 09:11:13

这仅仅是因为您没有在包含视图的项目中添加SQLite的SQLite包(意思是Windows 8项目)

票数 0
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/18940820

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