在MasterDetailPage中使用Autofac和Xamarin.Forms導航

Question

我想在Xamarin.Forms項目中使用Autofac。我成功創建了基本樣本，甚至使用ViewFactory來處理更復雜的樣本。

但是，我無法使用MasterDetailPage以及導航。

我正在使用由Jonathan Yates編寫的工廠和服務。你可以找到自己的代碼here

我的應用程序引導程序：

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有導航到TestViewModel2命令：

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

然而，隨着異常應用程序崩潰說

無法從源類型轉換爲目標類型。

這種情況發生在Navigator推送下一頁時。

堆棧跟蹤：

「在TestIoc.TestModule + <> c.b__0_0（）[0x00000]在C：\用戶\ dushyantb \文件\的Visual Studio 2015 \項目\ 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「

我做錯了什麼？

注意：當沒有MasterDetailPage時，導航工作。

Answer 1

請務必不要覆蓋PageResolver，例如。不採取喬納森使用替代他WeatherApp樣品中：

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

的PageResolver函數功能的核心組件的默認實現需要的MasterDetail場景照顧。見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; 
      } 
     ); 

我與喬納森的框架測試MasterDetail場景與NavigationPage DetailViews成功地。所以它應該工作。

在我的案例中，啓動代碼是

 protected override void ConfigureApplication(IContainer container) 
     { 

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

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

     } 

這意味着，我有一個MainPageView，這是一個MasterDetailPage和需要建立它的子視圖的護理：

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

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

     } 
    } 

的MenuPageViewModel還使用IViewFactory來切換MasterPages的詳細信息：

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>()); 
    } 

} 

希望這可以幫助。