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在ViewModel构造函数和导航中添加Api接口将停止工作

prism xamarin.forms xamarin c#

2

KalleP · 技术社区 · 7 年前

https://blog.qmatteoq.com/prism-for-xamarin-forms-basic-navigation-and-dependency-injection-part-2/

我这样做是为了让导航停止工作:

private readonly IService _Service;
private ObservableCollection<TodoItem> _topSeries;

public ObservableCollection<TodoItem> TopSeries
{
    get { return _topSeries; }
    set { SetProperty(ref _topSeries, value); }
}

这是构造器:

public SecondPageViewModel(IService Service, INavigationService navigationService)   
{
    _Service = Service;
    _navigationService = navigationService;
}

更新:

获取数据的我的服务类:

public class Service : IService
{

    public List<TodoItem> TodoList { get; private set; }
    HttpClient client;

    Service()
    {
        client = new HttpClient();
        client.MaxResponseContentBufferSize = 256000;
    }

    public async Task<List<TodoItem>> DataAsync()
    {

        TodoList = new List<TodoItem>();

        var uri = new Uri(string.Format(Constants.RestUrl, string.Empty));

        try
        {
            var response = await client.GetAsync(uri);
            if (response.IsSuccessStatusCode)
            {
                var content = await response.Content.ReadAsStringAsync();
                TodoList = JsonConvert.DeserializeObject<List<TodoItem>>(content);
                Debug.WriteLine(content);
            }
        }
        catch (Exception ex)
        {
            Debug.WriteLine(@"ERROR {0}", ex.Message);
        }

        return TodoList;
    }
}

这是我的App.Xaml.cs

protected override void RegisterTypes(IContainerRegistry containerRegistry)
{
    containerRegistry.RegisterForNavigation<NavigationPage>();
    containerRegistry.RegisterForNavigation<View.MainPage, MainPageViewModel>();
    containerRegistry.RegisterForNavigation<View.SecondPage, SecondPageViewModel>();
    containerRegistry.Register<IService, Service>();
}

public interface IService
{
    Task<List<TodoItem>> DataAsync();
}

这是我导航的方式(从listview单击):

private EventItem _selectedEvent { get; set; }
public EventItem SelectedEvent
{
    get { return _selectedEvent; }  
    set
    {
        if (_selectedEvent != value)
        {
            if (Device.RuntimePlatform == Device.iOS)
            {
                _selectedEvent = null;
            }
            else
            {
                _selectedEvent = value;
            }
            NavigationParameters navParams = new NavigationParameters();
            navParams.Add("PassedValue", _todoItem.name);

            _navigationService.NavigateAsync("SecondPage", navParams);
        }
    }
}

编辑:

1 回复 | 直到 7 年前

1

2

Wojciech Kulik 7 年前

根据您的代码,您声明了如下构造函数:

Service()
{
    // ...
}

internal . 定义如下:

内部类型或成员只能在同一文件中访问装配

Service.cs 您的导航无法工作,因为依赖项注入失败。要修复它,只需将访问修饰符更改为 public :

public Service()
{
    // ...
}