Question

我正在使用Caliburn Micro 2.0.0-alpha2开发一个简单的Crud应用程序（Windows 8.1商店应用程序）

我遇到了在视图模型之间导航，传递对象的问题。

我多次阅读

提出的解决方案

Anders Gustafsson（How to pass parameter to navigated view model with WinRT Caliburn.Micro?）

我试图让它适应我的范围。但是这个对象是空的。

我需要将从listView中选择的单个对象传递给我的crudPage。 crudPage由显示FormView的userControl组成。所以我想用传递对象的值初始化这个Form。 solution proposed

我认为问题是只有在创建ViewModel之后才初始化“参数”，但我不知道如何解决这个问题。

根据Anders Gustafsson的想法，有我的代码

TransporterListViewModel（来自数据库的传输器列表）

public class TransporterListViewModel : ViewModelBase
{
    public string Title { get; set; }
    public TransporterListViewModel(INavigationService navigationService)
        : base(navigationService)
    {
        LoadData();
    }

    public async void LoadData() {

        _transporters = await TransporterService.GetAll();
    }

    private BindableCollection<Transporter> _transporters;

    public BindableCollection<Transporter> Transporters
    {
        get
        {
            return this._transporters;
        }
        set
        {
            this._transporters = value;
            NotifyOfPropertyChange(() => this.Transporters);
        }
    }

    private Transporter _selectedItem;
    public Transporter SelectedItem
    {
        get 
        {

            return _selectedItem;
        }

        set
        {
            _selectedItem = value;
            NotifyOfPropertyChange(() => this.SelectedItem);

            navigationService.Navigated += NavigationServiceOnNavigated;
            navigationService.NavigateToViewModel<TransporterCrudPageViewModel>(_selectedItem;);
            navigationService.Navigated -= NavigationServiceOnNavigated;
        }
    }

    private static void NavigationServiceOnNavigated(object sender, NavigationEventArgs args)
    {
        FrameworkElement view;
        TransporterCrudPageViewModel transporterCrudPageViewModel;
        if ((view = args.Content as FrameworkElement) == null ||
            (transporterCrudPageViewModel = view.DataContext as TransporterCrudPageViewModel) == null) return;

        transporterCrudPageViewModel.InitializeTransporterForm(args.Parameter as Transporter);
    }

TransporterCrudViewModel（将UserControl加入初始化的页面）

public class TransporterCrudPageViewModel : ViewModelBase
{
    public string Title { get; set; }

    public Transporter Parameter { get; set; }
    public TransporterFormViewModel TransporterFormVM { get; set; }

    public async void InitializeTransporterForm(Transporter enumerable)
    {
        TransporterFormVM = new TransporterFormViewModel(navigationService, enumerable);
        await SetUpForm(enumerable);
    }

    public async Task SetUpForm(Transporter t){
        TransporterFormVM.trName = t.trName;
        TransporterFormVM.trUrl = t.trUrl;

    }
    public TransporterCrudPageViewModel(INavigationService navigationService)
        : base(navigationService)
    {
        Title = "TransporterCrud Page";
        //this.navigationService = navigationService;

        this.InitializeTransporterForm(Parameter);

    }

TransporterFormViewModel（要初始化的userContol）

    public class TransporterFormViewModel :ViewModelBase
{


    public string Title { get; set; }

    public Transporter Transporter { get; set; }

    public TransporterFormViewModel(INavigationService navigationService,Transporter trans)
        : base(navigationService)
    {
        Transporter = trans;
    }



    private string _trName;
    public string trName 
    {
        get
        {
            return _trName;
        }
        set
        {
            _trName = value;
            NotifyOfPropertyChange(() => trName);
        }
    }


    public string trCode { get; set; }
    public string trUrl { get; set; }

    public int trId { get; set; }

Answer 1

在构造函数TransporterCrudViewModel中，您有：

this.InitializeTransporterForm(Parameter);

其中Parameter是未初始化的Transporter类型的属性，您将使用InitializeTransporterForm参数调用方法null。然后，您将使用参数SetUpForm的空值调用Transporter t方法。我认为你应该以某种方式初始化这个属性。

然后，假设您继续使用此TransporterListViewModel课程

transporterCrudPageViewModel.InitializeTransporterForm(args.Parameter as Transporter);

在方法InitializeTransporterForm中，您不必将传递的参数设置为属性Parameter的值，如下所示：

public async void InitializeTransporterForm(Transporter enumerable)
{
     TransporterFormVM = new TransporterFormViewModel(navigationService, enumerable);
     this.Parameter = enumerable; //setting the Parameter property..
     await SetUpForm(enumerable);
}

除了这些注释之外，你应该在IDE中放置一个断点

transporterCrudPageViewModel.InitializeTransporterForm(args.Parameter as Transporter);

确保Parameter对象的属性NavigationEventArgs不为空。

Caliburn Micro：在ViewModel之间传递Object

1 个答案: