从 Windows Phone 8.1 通用应用中的视图模型导航到新页面 [英] Navigating to a new page from the View Model in Windows Phone 8.1 universal app

问题描述

我正在开发 Windows Phone 8.1 通用应用程序，并希望找到处理页面导航的最佳方式，而无需在背后的代码中包含大量逻辑.我想让代码在我的视图中尽可能整洁.响应按钮点击而导航到新页面的公认 MVVM 方式是什么?

I am working on a windows phone 8.1 universal app and want to find the best way of handling page navigations without having large amounts of logic in the code behind. I want to keep the code behind in my View as uncluttered as possible. What is the accepted MVVM way of navigating to a new page in response to a button click?

我目前必须从 ViewModel 向视图发送 RelayComnmand 消息，其中包含要导航到的页面的详细信息.这意味着后面的代码必须按如下方式接线:

I currently have to send a RelayComnmand message from the ViewModel to the view with the details of the page to navigate to. This means that the code behind has to be wired up as follows:

    public MainPage()
    {
      InitializeComponent();
      Messenger.Default.Register<OpenArticleMessage>(this, (article) => ReceiveOpenArticleMessage(article));
...
}

    private object ReceiveOpenArticleMessage(OpenArticleMessage article)
    {
     Frame.Navigate(typeof(ArticleView));
   }

这似乎不是最好的方法，尽管它确实有效.如何直接从 ViewModel 进行页面导航?我在我的项目中使用 MVVM-Light.

This just doesn't seem the best way although it does work. How can I do the page navigations directly from the ViewModel? I am using MVVM-Light in my project.

推荐答案

好的，我已经找到了这个问题的答案.进行了一些调查，但我最终找到了首选的 MVVM-Light 方法.无论如何，我不相信这个答案，但只是将其张贴在这里，以防人们正在寻找这个问题的答案.

Ok, I have found an answer to this question. Took a bit of investigation but I eventually found the preferred MVVM-Light way of doing this. I don't take credit for this answer in anyway but just posting it here in case people are looking for an answer to this question.

创建一个INavigationService接口如下:

Create an INavigationService interface as follows:

public interface INavigationService
{
    void Navigate(Type sourcePageType);
    void Navigate(Type sourcePageType, object parameter);
    void GoBack();
}

创建一个NavigationService类如下:

Create a NavigationService class as follows:

public class NavigationService : INavigationService
{
    public void Navigate(Type sourcePageType)
    {
        ((Frame)Window.Current.Content).Navigate(sourcePageType);
    }

    public void Navigate(Type sourcePageType, object parameter)
    {
        ((Frame)Window.Current.Content).Navigate(sourcePageType, parameter);
    }

    public void GoBack()
    {
        ((Frame)Window.Current.Content).GoBack();
    }
}

现在在 ViewModelLocator 中，像这样设置:

Now in the ViewModelLocator, set it up like this:

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance",
        "CA1822:MarkMembersAsStatic",
        Justification = "This non-static member is needed for data binding purposes.")]
    public MainViewModel Main
    {
        get
        {
            return ServiceLocator.Current.GetInstance<MainViewModel>();
        }
    }

    static ViewModelLocator()
    {
        ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);

        if (ViewModelBase.IsInDesignModeStatic)
        {
            SimpleIoc.Default.Register<INavigationService, Design.DesignNavigationService>();
        }
        else
        {
            SimpleIoc.Default.Register<INavigationService>(() => new NavigationService());
        }

        SimpleIoc.Default.Register<MainViewModel>();
    }

接下来为设计时设置导航服务，如下所示:

Next setup a navigation service for design time as follows:

public class DesignNavigationService : INavigationService
{
    // This class doesn't perform navigation, in order
    // to avoid issues in the designer at design time.

    public void Navigate(Type sourcePageType)
    {
    }

    public void Navigate(Type sourcePageType, object parameter)
    {
    }

    public void GoBack()
    {
    }
}

我的 MainViewModel 构造函数如下:

My MainViewModel constructor is as follows:

   public MainViewModel(INavigationService navigationService)
    {
        _navigationService = navigationService;

        ...

现在您可以简单地使用它在您的视图模型中导航:

Now you can simply use this to navigate in your viewmodel:

_navigationService.Navigate(typeof(WelcomeView));

有关原作者 Laurent Bugnion 的更多详细信息，请参阅本文和相关代码.http://msdn.microsoft.com/en-us/magazine/jj651572.aspx

For more details on the original author Laurent Bugnion see this article and associated code. http://msdn.microsoft.com/en-us/magazine/jj651572.aspx

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