在MasterDetailPage中使用Autofac和Xamarin.Forms导航

Question

我想在Xamarin.Forms项目中使用Autofac。我成功创建了基本样本，甚至使用ViewFactory来处理更复杂的样本。

但是，我无法使用MasterDetailPage以及导航。

我正在使用由Jonathan Yates编写的工厂和服务。你可以找到自己的代码here

我的应用程序引导程序：

protected override void ConfigureApplication(IContainer container) 
{ 
    var viewFactory = container.Resolve<IViewFactory>(); 
    var mainPage = viewFactory.Resolve<TestViewModel1>(); 

    var navigationPage = new NavigationPage(mainPage); 
    var masterPage = new ContentPage(); 
    masterPage.Title = "asd"; 
    _application.MainPage = new MasterDetailPage() 
    { 
     Master = masterPage, 
     Detail = navigationPage 

    }; 
} 

我TestViewModel1有导航到TestViewModel2命令：

ButtonCommand = new Command(async()=>await _navigator.PushAsync<TestViewModel2>());

然而，随着异常应用程序崩溃说

无法从源类型转换为目标类型。

这种情况发生在Navigator推送下一页时。

堆栈跟踪：

“在TestIoc.TestModule + <> c.b__0_0（）[0x00000]在C：\用户\ dushyantb \文件\的Visual Studio 2015 \项目\ TestIoc \ TestIoc \ TestIoc \ TestModule.cs：27 \ n at TestIoc.Views.PageProxy.get_Navigation（）[0x00001] in C：\ Users \ dushyantb \ Documents \ Visual Studio 2015 \ Projects \ TestIoc \ TestIoc \ TestIoc \ Views \ PageProxy.cs：39 \ n在TestIoc.Navigator.get_Navigation（）[0x00001]在C：\ Users \ dushyantb \ Documents \ Visual Studio 2015 \ Projects \ TestIoc \ TestIoc \ TestIoc \ Services \ Navigator.cs中：26 \ n在TestIoc.Navigator + d__8 `1 [TestIoc.ViewModels.TestViewModel2] .MoveNext（）[0x0003a] in C：\ Users \ dushyantb \ Documents \ Visual Studio 2015 \ Projects \ TestIoc \ TestIoc \ TestIoc \ Services \ Navigator.cs：58“

我做错了什么？

注意：当没有MasterDetailPage时，导航工作。

Answer 1

请务必不要覆盖PageResolver，例如。不采取乔纳森使用替代他WeatherApp样品中：

builder.RegisterInstance<Func<Page>>(() => ((NavigationPage)Application.Current.MainPage).CurrentPage); 

的PageResolver函数功能的核心组件的默认实现需要的MasterDetail场景照顾。见AutoFacModule.cs：

  // default page resolver 
      builder.RegisterInstance<Func<Page>>(() => 
      { 
       // Check if we are using MasterDetailPage 
       var masterDetailPage = Application.Current.MainPage as MasterDetailPage; 

       var page = masterDetailPage != null 
        ? masterDetailPage.Detail 
        : Application.Current.MainPage; 

       // Check if page is a NavigationPage 
       var navigationPage = page as IPageContainer<Page>; 

       return navigationPage != null 
        ? navigationPage.CurrentPage 
         : page; 
      } 
     ); 

我与乔纳森的框架测试MasterDetail场景与NavigationPage DetailViews成功地。所以它应该工作。

在我的案例中，启动代码是

 protected override void ConfigureApplication(IContainer container) 
     { 

      // set main page 
      var viewFactory = container.Resolve<IViewFactory>(); 

      var mainPage = viewFactory.Resolve<MainPageViewModel>(); 
      _application.MainPage = mainPage; 

     } 

这意味着，我有一个MainPageView，这是一个MasterDetailPage和需要建立它的子视图的护理：

public class MainPage : MasterDetailPage 
    { 
     public MainPage (IViewFactory viewfactory) 
     { 
      Master = viewfactory.Resolve<MenuPageViewModel>(); 

      Detail = new NavigationPage (viewfactory.Resolve<DetailViewModel1>()); 

     } 
    } 

的MenuPageViewModel还使用IViewFactory来切换MasterPages的详细信息：

public class MenuPageViewModel : ViewModelBase 
{ 
    IViewFactory _viewFactory; 
    public MenuPageViewModel (IViewFactory viewFactory) 
    { 
     _viewFactory = viewFactory; 

     ShowDetail1Command = new Command (ShowDetail1); 
     ShowDetail2Command = new Command (ShowDetail2); 
    } 


    public ICommand ShowDetail1Command { get; set;} 
    public void ShowDetail1() { 
     var mainPage = _viewFactory.Resolve<MainPageViewModel>(); 

     ((MasterDetailPage)mainPage).Detail = new NavigationPage (_viewFactory.Resolve<DetailViewModel1>()); 
    } 

    public ICommand ShowDetail2Command { get; set;} 
    public void ShowDetail2() { 
     var mainPage = _viewFactory.Resolve<MainPageViewModel>(); 

     ((MasterDetailPage)mainPage).Detail = new NavigationPage (_viewFactory.Resolve<DetailViewModel2>()); 
    } 

} 

希望这可以帮助。