Question

我想使用标签式导航和MvvmCross制作一个Xamarin原生应用。我正在使用这个项目作为参考：

https://github.com/MvvmCross/MvvmCross/tree/master/TestProjects/Playground/Playground.iOS

我让项目工作并成功将标签添加到我的应用程序中，但是，我不明白它是如何工作的。

在应用开始时，我加载TabsRootViewModel，如下所示：

public class TabsRootViewModel : MvxViewModel
{
    private readonly IMvxNavigationService _navigationService;

    public TabsRootViewModel(IMvxNavigationService navigationService)
    {
        _navigationService = navigationService ?? throw new ArgumentNullException(nameof(navigationService));
        ShowInitialViewModelsCommand = new MvxAsyncCommand(ShowInitialViewModels);
    }

    // Init and Start are important parts of MvvmCross' CIRS ViewModel lifecycle
    // Learn how to use Init and Start at https://github.com/MvvmCross/MvvmCross/wiki/view-model-lifecycle
    public void Init()
    {
    }

    public override void Start()
    {
    }

    public IMvxAsyncCommand ShowInitialViewModelsCommand { get; private set; }

    private async Task ShowInitialViewModels()
    {
        var tasks = new List<Task>();
        tasks.Add(_navigationService.Navigate<Tab1ViewModel>());
        tasks.Add(_navigationService.Navigate<Tab2ViewModel>());
        tasks.Add(_navigationService.Navigate<Tab3ViewModel>());
        await Task.WhenAll(tasks);
    }
}

在我的iOS项目中，我有一个TabsRootView，如下所示：

public partial class TabsRootView : MvxTabBarViewController<TabsRootViewModel>
{
    private bool _isPresentedFirstTime = true;

    public TabsRootView() : base()
    {
    }

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        // Perform any additional setup after loading the view, typically from a nib.
    }

    public override void ViewWillAppear(bool animated)
    {
        base.ViewWillAppear(animated);

        if (ViewModel != null && _isPresentedFirstTime)
        {
            _isPresentedFirstTime = false;
            ViewModel.ShowInitialViewModelsCommand.ExecuteAsync(null);
        }
    }
}

然后每个标签看起来像：

[MvxTabPresentation(TabName = "Tab1")]
public partial class Tab1View : MvxViewController
{
    public HistoryView() : base("Tab1View", null)
    {
    }

    public override void DidReceiveMemoryWarning()
    {
        base.DidReceiveMemoryWarning();

        // Release any cached data, images, etc that aren't in use.
    }

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        // Perform any additional setup after loading the view, typically from a nib.
    }
}

因此，ViewDidLoad调用ShowInitialViewModelsCommand上的方法ViewModel，这会以某种方式创建我期望的标签，并且一切正常。

我只是不明白ShowInitialViewModels中的方法TabsRootViewModel成功添加标签的方式或原因。我真的找不到任何最新的文档。任何人都能解释一下这是如何工作的吗？如果这是完成我想要做的事情的正确方法吗？

MvvmCross和选项卡式导航 - iOS

0 个答案: