从 MvvmCross 中的 Web 服务获取数据 Xamarin.iOS

Question

我正在尝试将 JSON 从 REST API 转换为 Xamarin.iOS。虽然我能够从 API 获取数据，但不知何故数据未填充到 TableView 中。

ViewModel

public class SchoolSelectionViewModel : BaseViewModel
{
    private readonly ISchoolNames _schoolService;
    public SchoolSelectionViewModel(ISchoolNames schoolService)
    {
        _schoolService = schoolService;
    }
    public override void Start()
    {
        IsLoading = true;
        _schoolService.GetFeedItems(OnDilbertItems, OnError);
    }

    private void OnDilbertItems(List<SchoolModel> list)
    {
        IsLoading = false;
        Items = list;
    }

    private void OnError(Exception error)
    {
        // not reported for now
        IsLoading = false;
    }

    private bool _isLoading;
    public bool IsLoading
    {
        get { return _isLoading; }
        set { _isLoading = value; RaisePropertyChanged(() => IsLoading); }
    }

    private List<SchoolModel> _items;
    public List<SchoolModel> Items
    {
        get { return _items; }
        set { _items = value; RaisePropertyChanged(() => Items); }
    }
    private MvvmCross.Core.ViewModels.MvxCommand<SchoolModel> _itemSelectedCommand;
    public System.Windows.Input.ICommand ItemSelectedCommand
    {
        get
        {
            _itemSelectedCommand = _itemSelectedCommand ?? new MvvmCross.Core.ViewModels.MvxCommand<SchoolModel>(DoSelectItem);
            return _itemSelectedCommand;
        }
    }

    private void DoSelectItem(SchoolModel item)
    {
        //ShowViewModel<DetailViewModel>(item);
    }
}

服务

public class SchoolNames : ISchoolNames
{
    public SchoolNames()
    {
    }
    public void GetFeedItems(Action<List<SchoolModel>> success, Action<Exception> error)
    {
        var url = "http://demo.imanage-school.com/api/configurations/schoolnames";

        var request = (HttpWebRequest)WebRequest.Create(url);
        try
        {
            request.BeginGetResponse(result => ProcessResponse(success, error, request, result), null);
        }
        catch (Exception exception)
        {
            error(exception);
        }
    }

    private void ProcessResponse(Action<List<SchoolModel>> success, Action<Exception> error, HttpWebRequest request, IAsyncResult result)
    {
        try
        {
            var response = request.EndGetResponse(result);
            using (var stream = response.GetResponseStream())
            using (var reader = new StreamReader(stream))
            {
                var json_data = reader.ReadToEnd();
                json_data = json_data.Replace("\"", string.Empty);
                json_data = json_data.Replace("\", "\"");

                //if (text.StartsWith("\""))
                //{
                //    text = text.Remove(0, 1);
                //}
                //if (text.EndsWith("\""))
                //{
                //    text = text.Remove(text.Length-1, 1);
                //}
                List<SchoolModel> List = new List<SchoolModel>();

                //List = JsonConvert.DeserializeObject < List <SchoolModel>> text;
                //List = JsonConvert.DeserializeObject(< List < SchoolModel >> text);
                var objects = JsonConvert.DeserializeObject<List<SchoolModel>>(json_data);
                success(List);
            }
        }
        catch (Exception exception)
        {
            error(exception);
        }
    }

    private List<SchoolModel> ParseDilbertItemList(string text)
    {
        var root = JsonConvert.DeserializeObject<SchoolModel>(text);
        var jsondetails = JsonConvert.SerializeObject(text);
        var xml = XDocument.Parse(text);
        var items = xml.Descendants("item");
        var list = items.Select(x =>
                                new SchoolModel()
                                {
            Name = x.Element("title").Value,
            ApiUrl = ExtractHttpImg(x.Element("description").Value)
                                }).ToList();
        return list;
    }

    private string ExtractHttpImg(string value)
    {
        var startPos = value.IndexOf("http://");
        var endPos = value.IndexOf(".gif\"", startPos);
        return value.Substring(startPos, endPos + 4 - startPos);
    }
}

ViewController

public partial class SchoolSelectionView : MvxViewController<SchoolSelectionViewModel>
{
    public SchoolSelectionView() : base("SchoolSelectionView", null)
    {
    }

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();
        this.NavigationController.SetNavigationBarHidden(true,true);

        var source = new MvxStandardTableViewSource(tblSchoolSelection, "TitleText Name");
        this.CreateBinding(source).To<SchoolSelectionViewModel>(vm => vm.Items).Apply();
        this.CreateBinding(source).For(s => s.SelectionChangedCommand).To<SchoolSelectionViewModel>(vm => vm.ItemSelectedCommand).Apply();
        tblSchoolSelection.Source = source;
        tblSchoolSelection.ReloadData();
    }

    public override void DidReceiveMemoryWarning()
    {
        base.DidReceiveMemoryWarning();
        // Release any cached data, images, etc that aren't in use.
    }
}

我觉得绑定有问题，但我无法修复它。

Answer 1

在您的服务中：

List<SchoolModel> List = new List<SchoolModel>();

//List = JsonConvert.DeserializeObject < List <SchoolModel>> text;
//List = JsonConvert.DeserializeObject(< List < SchoolModel >> text);

var objects = JsonConvert.DeserializeObject<List<SchoolModel>>(json_data);
success(List);

您首先创建一个变量 List，然后反序列化 JSON，但将其存储到新变量 objects 中。但是您随后将 List 传递给 success 方法，但 List 实际上是空的。您可能希望以 success(objects) 结尾以使其正常工作。

从 MvvmCross 中的 Web 服务获取数据 Xamarin.iOS

Getting data from web service in MvvmCross Xamarin.iOS

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xamarin.ios

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