在MVVMCross中将参数从Detail传递到MainViewModel

本文关键字：MainViewModel Detail MVVMCross 参数 | 更新日期: 2024-10-18 22:13:10

我有两个视图：MainView和DetailView。我有一个项目列表要显示，当用户选择一个项目时，我将项目属性传递给DetailViewModel，用户可以更新这些值。

到目前为止一切正常，但我想知道如何将更新后的值传递回MainViewModel？

MainViewModel.cs

public MainViewModel SelectedItem
{
  get { return _selectedItem; }
  set
  {
    _selectedItem = value;
    ShowViewModel<DetailViewModel>(
    new DetailViewModel.Parameter
    {
        Date = Date,
        Age = _selectedItem.Age,
        Category = _selectedItem.Category,
        Discount = _selectedItem.Discount,
      }
     );
    RaisePropertyChanged(() => SelectedItem);
  }
}

DetailViewModel.cs

public class DetailViewModel: MvxViewModel
{
    public double Age { get; set; }
    public double Category { get; set; }
    public double Discount { get; set; }
    public class Parameter
    {
        public DateTime Date { get; set; }
        public double Age { get; set; }
        public int Category{ get; set; }
        public double Discount { get; set; }
    }
    public void Init(Parameter param)
    {
        Age = param.Age;
        Category = param.Category;
        Discount = param.Discount ;
    }
}

在MVVMCross中将参数从Detail传递到MainViewModel

在ViewModels之间传递变量的一种方法是基于Messenger的解决方案。

MvvvmCross信使可以在NuGet中找到。

MainViewModel

private readonly IMvxMessenger _messenger;
private readonly MvxSubscriptionToken _token;
public MainViewModel(IMvxMessenger messenger) {
    _messenger = messenger;
    _token = messenger.Subscribe<SelectedItemMessage>(OnMessageReceived);;
}
private void OnMessageReceived(SelectedItemMessage obj)
{
    SelectedItem = obj.SelectedItem;
}

DetailViewModel

private readonly IMvxMessenger _messenger;
public DetailViewModel(IMvxMessenger messenger) {
    _messenger = messenger;
}
public void YourUpdateMethod() {
    var message = new SelectedItemMessage(this, SelectedItem); //SelectedItem assumed it is a ViewModel property.
    _messenger.Publish(message, typeof(SelectedItemMessage));
}

SelectedItemMessage

public class SelectedItemMessage : MvxMessage
{
    public SelectedItemMessage(object sender, SelectedItem selectedItem) : base(sender)
    {
        SelectedItem = selectedItem;
    }
    public SelectedItem SelectedItem { get; set; }
}

看看http://slodge.blogspot.nl/2013/05/n9-getting-message-n1-days-of-mvvmcross.htmlCCD_ 7的完整指南。

使用消息中的年龄和类别编辑

public SelectedItemMessage(object sender, double age, int category) : base(sender)
    {
        Age = age;
        Category = category;
    }
    public double Age { get; set; }
    public int Category{ get; set; }
}

更改MainViewModel OnMessageReceived方法

private void OnMessageReceived(SelectedItemMessage obj)
{
    Age = obj.Age;
    Category= obj.Category;
}

在MainViewModel中创建DetailViewModel时，为什么不保留对它的引用？然后，DetailViewModel实例中更改的任何值都将通过MainViewModel中的引用可用。

private DetailViewModel _detailVM;
public MainViewModel SelectedItem
{
  get { return _selectedItem; }
  set
  {
    _selectedItem = value;
    _detailVM = new DetailViewModel.Parameter {
        Date = Date,
        Age = _selectedItem.Age,
        Category = _selectedItem.Category,
        Discount = _selectedItem.Discount
    };
    ShowViewModel<DetailViewModel>(_detailVM);
    RaisePropertyChanged(() => SelectedItem);
  }
}
相关文章：