Question

我正在尝试将参数传递给子ViewModel构造函数，该构造函数抛出＆＃34; MvvmCross.Platform.Exceptions.MvxException：无法构造和初始化ViewModel ... MvxIoCResolveException：无法解析MyType类型的参数myParam的参数...＆＃34;

MyChildViewModel.cs

public class MyChildViewModel : MvxViewModel
{
    private MyType _myParam;
    public MyType MyParam
    {
        get { return _myParam; }
        set
        {
            if (SetProperty(ref _myParam, value))
            {
                RaisePropertyChanged(() => MyParam);
            }
        }
    }

    public MyChildViewModel(MyType myParam)
    {
        _myParam = myParam;
    }

}

在我的父ViewModel中，我有：

public ICommand ShowDialogCommand { get; private set; }
ShowDialogCommand = new MvxCommand<MyType>(e => ShowViewModel<MyChildViewModel>(e));

家长活动电话：

ViewModel.ShowDialogCommand.Execute(VarOfMyType);

我显然做错了什么。这种甚至可以远程接受的方法将数据传递给子ViewModel吗？什么是最佳做法？

提前感谢你宝贵的时间。

Answer 1

如果您阅读了文档使用MvxNavigationService传递对象很容易：https://www.mvvmcross.com/documentation/fundamentals/navigation

请注意，该文档适用于目前每晚发布的MvvmCross 5.2，但5.0及以后版本几乎相同。

在您的ViewModel中，这可能如下所示：

public class MyViewModel : MvxViewModel
{
    private readonly IMvxNavigationService _navigationService;
    public MyViewModel(IMvxNavigationService navigationService)
    {
        _navigationService = navigationService;
    }

    public override void Prepare()
    {
        //Do anything before navigating to the view
    }

    public async Task SomeMethod()
    {
        await _navigationService.Navigate<NextViewModel, MyObject>(new MyObject());
    }
}

public class NextViewModel : MvxViewModel<MyObject>
{
    public override void Prepare(MyObject parameter)
    {
        //Do anything before navigating to the view
        //Save the parameter to a property if you want to use it later
    }

    public override async Task Initialize()
    {
        //Do heavy work and data loading here
    }
}

Answer 2

从他们this website的方式来看（根据你的情况进行调整和修改）：

public ICommand ShowDialogCommand { get; private set; }
ShowDialogCommand = new MvxCommand<MyType>(ShowMyVM);

private void ShowMyVM(MyType e)
{
    if (e != null)
        ShowViewModel<SingleClientViewModel>(e);
    else
    {
        //handle case where your parameter is null
    }
}

MVVMCROSS - 将参数传递给ViewModel

2 个答案: