解析c#中异步检索数据的方法，如何访问数据

本文关键字：数据 何访问 访问 方法 异步 检索 解析 | 更新日期: 2023-09-27 18:12:33

我试图检索一个简单的查询解析和添加自定义适配器上的内容，但我可以弄清楚它是如何，我从文档中看到，只有与异步我可以得到数据，但我怎么能添加数据后到适配器，如果异步方法总是返回空?这是我正在尝试的，但不工作

public class BusinessListFragment : Fragment
{
    private List<Business> _list;
    ListView businessListView;
    public async override void OnResume()
    {
        base.OnResume();
        _list = await GetData();
    }
    public override View OnCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        var view = inflater.Inflate(Resource.Layout.BusinessList, container, false);
        businessListView = view.FindViewById<ListView>(Resource.Id.businessListView);
        var adapter = new BusinessListAdapter(Activity, _list);
        businessListView.Adapter = adapter;
        adapter.NotifyDataSetChanged ();
        return view;
    }
    public async Task<List<Business>> GetData(){
        var query = ParseObject.GetQuery("Business");
        IEnumerable<ParseObject> results = await query.FindAsync();
        var data = new List<Business>();
        foreach (var temp in results)
        {
            var _business = new Business();
            // This does not require a network access.
            _business.Name = temp.Get<string>("name");
            _business.Address = temp.Get<string>("address");
            _business.Town = temp.Get<string>("town");
            _business.Country = temp.Get<string>("country");
            data.Add (_business);
        }
        return data;
    }
}

我做错了什么?应该是非常简单的

解析c#中异步检索数据的方法，如何访问数据

你通常不需要使用async和await的显式任务方法——它们被引入c#是专门为了简化这类问题。

public override View OnCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        var view = inflater.Inflate(Resource.Layout.BusinessList, container, false);
        businessListView = view.FindViewById<ListView>(Resource.Id.businessListView);
        _list = await GetData();
        var adapter = new BusinessListAdapter(Activity, _list);
        businessListView.Adapter = adapter;
        adapter.NotifyDataSetChanged ();
        return view;
    }
    public async Task<List<Business>> GetData(){
        var query = ParseObject.GetQuery("Business");
        IEnumerable<ParseObject> results = await query.FindAsync();
        var data = new List<Business>();
        foreach (var temp in results)
        {
            var _business = new Business();
            // This does not require a network access.
            _business.Name = temp.Get<string>("name");
            _business.Address = temp.Get<string>("address");
            _business.Town = temp.Get<string>("town");
            _business.Country = temp.Get<string>("country");
            data.Add (_business);
        }
      return data;
    }

事实证明，我不必返回数据，我可以用这种方式在我的GetData()方法中重新创建并填充适配器:

Activity.RunOnUiThread(() =>{
        var adapter = new BusinessListAdapter(Activity, data);
        businessListView.Adapter = adapter;
        adapter.NotifyDataSetChanged();
            Console.WriteLine ("name="+data.Count.ToString());
        });

谢谢大家的帮助

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