在我最近发表的一篇文章之后，建议使用主持人

Question

在我发布了一个星期前发布的问题之后，我使用MVVMCross的WPF应用程序，开始阅读有关演示者的工作方式。关于如何使用移动应用程序做某事的文档和视频很多，尤其是iOS，但对于桌面Windows WPF应用程序不多。根据n = 24视频，我创建了一个我从mvxsimplewpfviewpresenter派生的主持人，然后继续覆盖存在的函数（system.windows.frameworkelement Frameworkelement），其中主窗口将显示我的主视图和我要调用的所有其他视图，将在我的主视图下显示其内容：

  public class MyPresenter : Cirrious.MvvmCross.Wpf.Views.MvxSimpleWpfViewPresenter
  {
    private Window _mainWindow = null;
    private MvxWpfView _firstView = null;
    public MyPresenter(Window mainWindow)
      : base(mainWindow)
    {
      _mainWindow = mainWindow;
    }
    public override void Present(System.Windows.FrameworkElement frameworkElement)
    {
      //_mainWindow.DisplayGrid
      if(_firstView == null &&
         frameworkElement is FirstView)
      {
        _firstView = frameworkElement as FirstView;
        _mainWindow.Content = _firstView;
      }
      else if(_firstView != null)
      {
        if ((_firstView as FirstView).DisplayGrid.Children.Count > 0)
        {
          (_firstView as FirstView).DisplayGrid.Children.RemoveAt(0);
        }
        (_firstView as FirstView).DisplayGrid.Children.Add(frameworkElement);
      }
    }

我的主视图（称为firstViewModel）看起来像：

  public class FirstViewModel : MvxViewModel
  {
    public ICommand BlueCommand
    {
      get { return new MvxCommand(() => ShowViewModel<BlueViewModel>()); }
    }
    public ICommand RedCommand
    {
      get { return new MvxCommand(() => ShowViewModel<RedViewModel>()); }
    }
  }

，我的第一视图看起来像这样（在XAML中）：

    <views:MvxWpfView 
             x:Class="WpfApplication1.Views.FirstView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:views="clr-namespace:Cirrious.MvvmCross.Wpf.Views;assembly=Cirrious.MvvmCross.Wpf"
             mc:Ignorable="d" Height="Auto" Width="Auto">
  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="Auto" />
      <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
      <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>
    <Menu Grid.Row="0">
      <MenuItem Name="RedCommandMenuItem" Header="Red command" Command="{Binding Path=RedCommand}" />
      <MenuItem Name="BlueCommandMenuItem" Header="Blue command" Command="{Binding Path=BlueCommand}" />
    </Menu>
    <Grid Name="DisplayGrid" Grid.Row="1">
    </Grid>
  </Grid>
</views:MvxWpfView>

之后，我使我的演示者成为一个要使用的代替默认设备，并能够用红色背景显示视图，而从我的主视图中带有蓝色背景的视图，其中包含菜单。因此，这本质上可以很好地与我想做的事情一起使用。

所以我要去哪里？我想知道的是，这与我看到的所有其他示例都大不相同，这些示例使用了主持人的显示方法，您需要使用MVX。MVXSIMPLEWPFVIEWPRESENTER和MVXSIMPLEWPFFVIEWPRESENTER类都无法覆盖。通过调用命令，ShowViewModel呼叫演示者（我假定）以显示我的新视图，但是当我获得Frameworkelement时，我不必在此处呼吁解决。我试图理解背后的机制，以便更好地调试我应该有问题。.是否有与上一篇文章中提到的容器有任何链接？

谢谢

Answer 1

那么决心在哪里完成？

这是在基本MvxWpfViewPresenter

中完成的

public abstract class MvxWpfViewPresenter
    : IMvxWpfViewPresenter
{
    public void Show(MvxViewModelRequest request)
    {
        try
        {
            var loader = Mvx.Resolve<IMvxSimpleWpfViewLoader>();
            var view = loader.CreateView(request);
            Present(view);
        }
        catch (Exception exception)
        {
            MvxTrace.Error("Error seen during navigation request to {0} - error {1}", request.ViewModelType.Name,
                           exception.ToLongString());
        }
    }
    public abstract void Present(FrameworkElement frameworkElement);
    public virtual void ChangePresentation(MvxPresentationHint hint)
    {
        MvxTrace.Warning("Hint ignored {0}", hint.GetType().Name);
    }
}

https://github.com/mvvmcross/mvvmcross/blob/v3.1/cirrious/cirrious/cirrious.mvvmcross.wpf/views/mvxwpfvviewperpresenter.cs

Show可能是此类中的virtual - 但这是一个非常简单的类，我一直期望WPF用户只能编写自己的IMvxWpfViewPresenter

的版本

上一篇文章中提到的容器有任何链接？

WPF的默认容器是：

public class MvxWpfViewsContainer
    : MvxViewsContainer
    , IMvxWpfViewsContainer
{
    public FrameworkElement CreateView(MvxViewModelRequest request)
    {
        var viewType = GetViewType(request.ViewModelType);
        if (viewType == null)
            throw new MvxException("View Type not found for " + request.ViewModelType);
        // , request
        var viewObject = Activator.CreateInstance(viewType);
        if (viewObject == null)
            throw new MvxException("View not loaded for " + viewType);
        var wpfView = viewObject as IMvxWpfView;
        if (wpfView == null)
            throw new MvxException("Loaded View does not have IMvxWpfView interface " + viewType);
        var viewControl = viewObject as FrameworkElement;
        if (viewControl == null)
            throw new MvxException("Loaded View is not a FrameworkElement " + viewType);
        var viewModelLoader = Mvx.Resolve<IMvxViewModelLoader>();
        wpfView.ViewModel = viewModelLoader.LoadViewModel(request, null);
        return viewControl;
    }
}

来自https://github.com/mvvmcross/mvvmcross/blob/v3.1/cirrious/cirrious/cirrious.mvvmcross.wpf/views/mvxwpfvewpfvviewewscontainer.cs

它从https://github.com/mvvmcross/mvvmcross/blob/v3.1/cirrious/cirrious/cirrious.mvvmcross/views/mvxviews/mvxviewscontainer.cs-

在设置过程中，容器中使用反射填充Type s-请参见https://github.com/mvvmcross/mvvmcross/mvvmcross/wiki/customising-customising-uspemising-uspomis-set-----------------------------wik---wik--------------参见 InitalizeViewLookup信息。-ViewModel-associations