卡利微：通过视图模型之间的对象 [英] Caliburn Micro : passing Object between ViewModel

问题描述

我正在开发使用微卡利2.0.0-α2

我在麻烦的ViewModels之间的导航一个简单的CRUD应用程序（在Windows 8.1存储应用程序） ，传递对象。

我读到

提出的解决方案多次

安德斯古斯塔夫松（如何参数传递到导航的鉴于与WinRT的Caliburn.Micro？）

和我的模型试图将其适应范围我。
，而对象是alwais空。

我需要通过从一个ListView我crudPage选定一个对象。
的crudPage是由表示FormView控件的用户控件组成。
所以我想初始化此形式，传递的对象的值。

我认为，问题是，参数创建视图模型后才被初始化，但我不知道如何解决这个问题。

有是我的代码，根据安德斯·古斯塔夫松的想法

TransporterListViewModel（从数据库转运的列表）

 公共类TransporterListViewModel：ViewModelBase 
 {
公共字符串名称{搞定;组; } 
公共TransporterListViewModel（INavigationService的NavigationService）
：底座（的NavigationService）
 {
 LoadData（）; 
} 
 
公共异步无效LoadData（）{
 
 _transporters =等待TransporterService.GetAll（）; 
} 
 
私人BindableCollection<转运GT; _transporters; 
 
公共BindableCollection<转运GT;转运
 {
得到
 {
返回this._transporters; 
} 
组
 {
 this._transporters =价值; 
 NotifyOfPropertyChange（（）=> this.Transporters）; 
} 
} 
 
私人运输车_selectedItem; 
公共运输车的SelectedItem 
 {
得到
 {
 
返回_selectedItem; 
} 
 
组
 {
 _selectedItem =价值; 
 NotifyOfPropertyChange（（）=> this.SelectedItem）; 
 
 navigationService.Navigated + = NavigationServiceOnNavigated; 
 navigationService.NavigateToViewModel< TransporterCrudPageViewModel>（_将selectedItem;）; 
 navigationService.Navigated  -  = NavigationServiceOnNavigated; 
} 
} 
 
私有静态无效NavigationServiceOnNavigated（对象发件人，NavigationEventArgs参数）
 {
 FrameworkElement的观点; 
 TransporterCrudPageViewModel transporterCrudPageViewModel; 
如果（（查看= args.Content为FrameworkElement的）== NULL || 
（transporterCrudPageViewModel = view.DataContext为TransporterCrudPageViewModel）== NULL）回报; 
 
 transporterCrudPageViewModel.InitializeTransporterForm（args.Parameter作为转运）; 
} 
  

TransporterCrudViewModel（该页面cointains的用户控件初始化）

 公共类TransporterCrudPageViewModel：ViewModelBase 
 {
公共字符串名称{搞定;组; } 
 
公共运输车参数{搞定;组; } 
公共TransporterFormViewModel TransporterFormVM {搞定;组; } 
 
公共异步无效InitializeTransporterForm（转运枚举）
 {
 TransporterFormVM =新TransporterFormViewModel（的NavigationService，枚举）; 
等待SetUpForm（枚举）; 
} 
 
公共异步任务SetUpForm（转运T）{
 TransporterFormVM.trName = t.trName; 
 TransporterFormVM.trUrl = t.trUrl; 
 
} 
公共TransporterCrudPageViewModel（INavigationService的NavigationService）
：底座（的NavigationService）
 {
标题=TransporterCrud页; 
 //this.navigationService =的NavigationService; 
 
 this.InitializeTransporterForm（参数）; 
 
} 
  

TransporterFormViewModel（该userContol初始化）

 公共类TransporterFormViewModel：ViewModelBase 
 {
 
 
公共字符串名称{搞定;组; } 
 
公共运输车转运{搞定;组; } 
 
公共TransporterFormViewModel（INavigationService的NavigationService，转运反式）
：底座（的NavigationService）
 {
运输车=反; 
} 
 
 
 
私人字符串_trName; 
公共字符串段trname 
 {
得到
 {
返回_trName; 
} 
组
 {
 _trName =价值; 
 NotifyOfPropertyChange（（）=>段trname）; 
} 
} 
 
 
公共字符串trCode {搞定;组; } 
公共字符串trUrl {搞定;组; } 
 
公众诠释TRID {搞定;组; } 
  

解决方案

在构造函数中 TransporterCrudViewModel 类有：

  this.InitializeTransporterForm（参数）; 
  

其中，参数是类型的属性运输车没有初始化，你会调用该方法 InitializeTransporterForm 与空参数。然后你会打电话给 SetUpForm 方法，参数运输车牛逼的空值。我想你应该以某种方式这个属性初始化。

然后，假设你在你的 TransporterListViewModel 类继续与此：

  transporterCrudPageViewModel.InitializeTransporterForm（args.Parameter作为转运）; 
  

在方法 InitializeTransporterForm ，你不t将传递的参数作为属性的值参数的东西是这样的：

 公共异步无效InitializeTransporterForm（转运枚举）
 {
 TransporterFormVM =新TransporterFormViewModel（的NavigationService，枚举）; 
 this.Parameter =枚举; //设置参数属性.. 
等待SetUpForm（枚举）; 
} 
  

除了这些笔记，你应该把断点与你的IDE中的行

  transporterCrudPageViewModel.InitializeTransporterForm（args.Parameter作为转运）; 
  

确认该财产参数的 NavigationEventArgs 对象不为null。

I'm developing a simple Crud Application (a windows 8.1 store application) using Caliburn Micro 2.0.0-alpha2

I'm in trouble with navigation between viewmodels, passing object.

I read many times the solution proposed by

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

and i tried to adapt it to my scope. But the object is alwais null.

I need to pass a single object selected from a listView to my crudPage. The crudPage is composed by an userControl that shown the FormView. So i want to initialize this Form, with the values of the passed object.

I think that the problem is that the "Parameter" is initialized only after the ViewModel is created, but i don't know how to fix that problem.

There is my code, according with the idea of Anders Gustafsson

TransporterListViewModel (a list of Transporters from Database)

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 (the page that cointains the UserControl to initialize)

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 (the userContol to initialize)

    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; }

解决方案

In the constructor TransporterCrudViewModel class you have:

this.InitializeTransporterForm(Parameter);

where Parameter is a property of type Transporter not initialized and you will call the method InitializeTransporterForm with a null parameter. Then you'll call SetUpForm method with a null value of the parameter Transporter t. I think you should initialize in some way this property.

Then, supposing you're continuing in your TransporterListViewModel class with this:

transporterCrudPageViewModel.InitializeTransporterForm(args.Parameter as Transporter);

in the method InitializeTransporterForm, you don't set the passed parameter as value of the property Parameter with something like this:

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

Beside these notes, you should put a breakpoint with your IDE in the line

transporterCrudPageViewModel.InitializeTransporterForm(args.Parameter as Transporter);

Make sure that the property Parameter of the NavigationEventArgs object is not null.

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