Caliburn.Micro + MEF +现代用户界面：IContent事件

Question

我已经使用Caliburn.Micro和Modern UI（https://mui.codeplex.com）开始了一个项目，并且在我的视图模型上触发IContent的导航事件时遇到了一些困难。我已经让两个人联系起来，与以下人员合作：

CM Bootstrapper：

public class CMBootstrapper : Bootstrapper<IShell> {
    private CompositionContainer container;
    private DirectoryCatalog catalog;

    public CMBootstrapper() { }

    protected override void Configure() {
        catalog = new DirectoryCatalog(".", "*.*");
        container = new CompositionContainer(catalog);

        var compositionBatch = new CompositionBatch();
        compositionBatch.AddExportedValue<IWindowManager>(new WindowManager());
        compositionBatch.AddExportedValue<IEventAggregator>(new EventAggregator());
        compositionBatch.AddExportedValue(container);
        container.Compose(compositionBatch);
    }

    protected override IEnumerable<Assembly> SelectAssemblies() {
        List<Assembly> assemblies = new List<Assembly>();
        assemblies.Add(Assembly.GetExecutingAssembly());
        return assemblies;
    }

    protected override object GetInstance(Type serviceType, string key) {
        string contract = string.IsNullOrEmpty(key) ? AttributedModelServices.GetContractName(serviceType) : key;
        var exports = container.GetExportedValues<object>(contract);

        if (exports.Count() > 0)
            return exports.First();

        throw new Exception(string.Format("Could not locate any instances of contract {0}.", contract));
    }

    protected override IEnumerable<object> GetAllInstances(Type serviceType) {
        return container.GetExportedValues<object>(AttributedModelServices.GetContractName(serviceType));
    }

    protected override void BuildUp(object instance) {
        container.SatisfyImportsOnce(instance);
    }
}

现代UI内容加载器：

[Export]
public class MuiContentLoader : DefaultContentLoader {
    protected override object LoadContent(Uri uri) {
        var content = base.LoadContent(uri);
        if (content == null)
            return null;

        // Locate VM
        var viewModel = ViewModelLocator.LocateForView(content);

        if (viewModel == null)
            return content;

        // Bind VM
        if (content is DependencyObject)
            ViewModelBinder.Bind(viewModel, content as DependencyObject, null);

        return content;
    }
}

MuiView.xaml（Shell）

<mui:ModernWindow x:Class="XMOperations.Views.MuiView"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mui="http://firstfloorsoftware.com/ModernUI"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         ContentLoader="{StaticResource ModernContentLoader}"
         d:DesignHeight="300" d:DesignWidth="300">

<mui:ModernWindow.TitleLinks>
    <mui:Link DisplayName="Settings" Source="/Views/SettingsView.xaml" />
</mui:ModernWindow.TitleLinks>

<mui:ModernWindow.MenuLinkGroups>
    <mui:LinkGroupCollection>
        <mui:LinkGroup GroupName="Hello" DisplayName="Hello">
            <mui:LinkGroup.Links>
                <mui:Link Source="/Views/ChildView.xaml" DisplayName="Click me"></mui:Link>
            </mui:LinkGroup.Links>
        </mui:LinkGroup>
    </mui:LinkGroupCollection>
</mui:ModernWindow.MenuLinkGroups>

MuiViewModel

[Export(typeof(IShell))]
public class MuiViewModel : Conductor<IScreen>.Collection.OneActive, IShell {

}

导出每个子视图并实现IContent，如下所示：

[Export]
[PartCreationPolicy(CreationPolicy.Shared)]
public class SettingsViewModel : Screen, IContent {

    #region IContent Implementation

    public void OnFragmentNavigation(FragmentNavigationEventArgs e) {
        Console.WriteLine("SettingsViewModel.OnFragmentNavigation");
    }

    public void OnNavigatedFrom(NavigationEventArgs e) {
        Console.WriteLine("SettingsViewModel.OnNavigatedFrom");
    }

    public void OnNavigatedTo(NavigationEventArgs e) {
        Console.WriteLine("SettingsViewModel.OnNavigatedTo");
    }

    public void OnNavigatingFrom(NavigatingCancelEventArgs e) {
        Console.WriteLine("SettingsViewModel.OnNavigatingFrom");
    }

    #endregion
}

但这些都没有开火。经过一些调试后，我发现ModernFrame正在检查(SettingsView as IContent)的事件，因为它只是一个简单的UserControl而没有它们。所以我创建了一个自定义UserControl类，试图将事件传递给ViewModel：

MuiContentControl

public delegate void FragmentNavigationEventHandler(object sender, FragmentNavigationEventArgs e);
public delegate void NavigatedFromEventHandler(object sender, NavigationEventArgs e);
public delegate void NavigatedToEventHandler(object sender, NavigationEventArgs e);
public delegate void NavigatingFromEventHandler(object sender, NavigatingCancelEventArgs e);

public class MuiContentControl : UserControl, IContent {
    public event FragmentNavigationEventHandler FragmentNavigation;
    public event NavigatedFromEventHandler NavigatedFrom;
    public event NavigatedToEventHandler NavigatedTo;
    public event NavigatingFromEventHandler NavigatingFrom;

    public MuiContentControl() : base() {

    }

    public void OnFragmentNavigation(FragmentNavigationEventArgs e) {
        if(FragmentNavigation != null)
            FragmentNavigation(this, e);
    }

    public void OnNavigatedFrom(NavigationEventArgs e) {
        if (NavigatedFrom != null)
            NavigatedFrom(this, e);
    }

    public void OnNavigatedTo(NavigationEventArgs e) {
        if(NavigatedTo != null)
            NavigatedTo(this, e);
    }

    public void OnNavigatingFrom(NavigatingCancelEventArgs e) {
        if(NavigatingFrom != null)
            NavigatingFrom(this, e);
    }
}

然后我修改了视图以使用Message.Attach监听事件：

SettingsView

<local:MuiContentControl x:Class="XMOperations.Views.SettingsView"
         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:mui="http://firstfloorsoftware.com/ModernUI" 
         xmlns:cal="http://www.caliburnproject.org"
         xmlns:local="clr-namespace:XMOperations"
         cal:Message.Attach="[Event FragmentNavigation] = [Action OnFragmentNavigation($source, $eventArgs)];
                             [Event NavigatedFrom] = [Action OnNavigatedFrom($source, $eventArgs)];
                             [Event NavigatedTo] = [Action OnNavigatedTo($source, $eventArgs)];
                             [Event NavigatingFrom] = [Action OnNavigatingFrom($source, $eventArgs)]"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid Style="{StaticResource ContentRoot}">
    <mui:ModernTab SelectedSource="/Views/Settings/AppearanceView.xaml" Layout="List" ContentLoader="{StaticResource ModernContentLoader}">
        <mui:ModernTab.Links>
            <mui:Link DisplayName="Appearance" Source="/Views/Settings/AppearanceView.xaml" />
        </mui:ModernTab.Links>
    </mui:ModernTab>
</Grid>

唯一不会触发的事件是NavigatedTo所以我相信在调度事件之后才会应用Message.Attach。我可能这样做的方式非常错误，并且可以进行大规模的重建。

Answer 1

好的，这最终并没有那么糟糕 - 它确实让生活变得更容易，试图将事件传递给VM

我为ModernFrame控件模板中存在的ModernWindow控件创建了指挥

您需要在VM的OnViewLoaded事件中为ModernWindow创建指挥实例，因为这似乎是最佳位置（即尚未发生导航但控件已完全加载并解决了它的模板）

// Example viewmodel:

public class ModernWindowViewModel : Conductor<IScreen>.Collection.OneActive
{
    protected override void OnViewLoaded(object view)
    {
        base.OnViewLoaded(view);

        // Instantiate a new navigation conductor for this window
        new FrameNavigationConductor(this);
    }
}

指挥代码如下：

public class FrameNavigationConductor
{
    #region Properties

    // Keep a ref to the frame
    private readonly ModernFrame _frame;

    // Keep this to handle NavigatingFrom and NavigatedFrom events as this functionality
    // is usually wrapped in the frame control and it doesn't pass the 'old content' in the
    // event args
    private IContent _navigatingFrom;

    #endregion

    public FrameNavigationConductor(IViewAware modernWindowViewModel)
    {
        // Find the frame by looking in the control template of the window
        _frame = FindFrame(modernWindowViewModel);

        if (_frame != null)
        {
            // Wire up the events
            _frame.FragmentNavigation += frame_FragmentNavigation;
            _frame.Navigated += frame_Navigated;
            _frame.Navigating += frame_Navigating;
        }
    }

    #region Navigation Events

    void frame_Navigating(object sender, NavigatingCancelEventArgs e)
    {
        var content = GetIContent(_frame.Content);

        if (content != null)
        {
            _navigatingFrom = content;
            _navigatingFrom.OnNavigatingFrom(e);
        }
        else
            _navigatingFrom = null;
    }

    void frame_Navigated(object sender, NavigationEventArgs e)
    {
        var content = GetIContent(_frame.Content);

        if (content != null)
            content.OnNavigatedTo(e);

        if (_navigatingFrom != null)
            _navigatingFrom.OnNavigatedFrom(e);

    }

    void frame_FragmentNavigation(object sender, FragmentNavigationEventArgs e)
    {
        var content = GetIContent(_frame.Content);

        if (content != null)
            content.OnFragmentNavigation(e);

    }

    #endregion

    #region Helpers

    ModernFrame FindFrame(IViewAware viewAware)
    {
        // Get the view for the window
        var view = viewAware.GetView() as Control;

        if (view != null)
        {
            // Find the frame by name in the template
            var frame = view.Template.FindName("ContentFrame", view) as ModernFrame;

            if (frame != null)
            {
                return frame;
            }
        }

        return null;
    }

    private IContent GetIContent(object source)
    {
        // Try to cast the datacontext of the attached viewmodel to IContent
        var fe = (source as FrameworkElement);

        if (fe != null)
        {
            var content = fe.DataContext as IContent;

            if (content != null)
                return content;
        }

        return null;
    }

    #endregion
}

现在，只要导航发生，您添加IContent接口的任何视图都会自动获取框架调用的方法

public class TestViewModel : Conductor<IScreen>, IContent
{
    public void OnFragmentNavigation(FragmentNavigationEventArgs e)
    {
        // Do stuff
    }

    public void OnNavigatedFrom(NavigationEventArgs e)
    {
        // Do stuff
    }

    public void OnNavigatedTo(NavigationEventArgs e)
    {
        // Do stuff
    }

    public void OnNavigatingFrom(NavigatingCancelEventArgs e)
    {
        // Do stuff
    }
}

我已经过测试，这适用于IContent上显示的所有4个导航事件 - 因为它通过EventArgs你可以直接从VM取消导航事件或做任何你想做的事情在仅查看场景中执行

我认为这可能是我能想到的最无痛的方式 - 在窗口中实际上是一行代码并在VM上实现接口，你就完成了：）

编辑：

我唯一可能添加的是在将导体添加到窗口时抛出或者调试日志通知，以防由于某种原因无法找到帧（可能是帧的名称可能会更改）在m：ui）的后续版本中

Answer 2

我按照我的IContent Views进行了操作，并在我的ViewModel上实现了IContent。

   public void OnFragmentNavigation(FirstFloor.ModernUI.Windows.Navigation.FragmentNavigationEventArgs e)
    {
        if (this.DataContext != null)
        {
            var viewModel = this.DataContext as IContent;
            if (viewModel != null)
            {
                viewModel.OnFragmentNavigation(e);
            }
        }
    }

    public void OnNavigatedFrom(FirstFloor.ModernUI.Windows.Navigation.NavigationEventArgs e)
    {
        if (this.DataContext != null)
        {
            var viewModel = this.DataContext as IContent;
            if (viewModel != null)
            {
                viewModel.OnNavigatedFrom(e);
            }
        }
    }

    public void OnNavigatedTo(FirstFloor.ModernUI.Windows.Navigation.NavigationEventArgs e)
    {
        if (this.DataContext != null)
        {
            var viewModel = this.DataContext as IContent;
            if (viewModel != null)
            {
                viewModel.OnNavigatedTo(e);
            }
        }
    }

    public void OnNavigatingFrom(FirstFloor.ModernUI.Windows.Navigation.NavigatingCancelEventArgs e)
    {
        if (this.DataContext != null)
        {
            var viewModel = this.DataContext as IContent;
            if (viewModel != null)
            {
                viewModel.OnNavigatingFrom(e);
            }

        }
    }