Question

我在Visual Studio 2013中使用Windows Phone Databound应用程序创建应用程序。我正在使用如下的ObservableCollection：

public ObservableCollection<ItemViewModel> Items { get; private set; }

，此Items是LongListSelector的ItemSource。

一旦应用程序启动一切正常。在我的应用中，应用栏中有一个刷新按钮。我想，当我点击刷新按钮时，ObservableCollection将显示更新的值，但ObservableCollection不刷新。

点击刷新按钮，我正在调用App.ViewModel.LoadData();函数，它以json格式从网上下载一些信息。

我正在使用的代码如下：

public void LoadData()
        {
            if( IsDataLoaded )
                this.Items = new ObservableCollection<ItemViewModel>();

            WebClient webClient = new WebClient();
            webClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(webClient_DownloadStringCompleted);
            webClient.DownloadStringAsync(new System.Uri("http://questoons.com/"));                     
        }
private void webClient_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
    if (e.Error != null)
    {
        System.Windows.Deployment.Current.Dispatcher.BeginInvoke(() =>
        {
            // Showing the exact error message is useful for debugging. In a finalized application, 
            // output a friendly and applicable string to the user instead. 
            System.Windows.MessageBox.Show(e.Error.Message);
        });
    }
    else
    {
       //System.Windows.Data.CollectionViewSource.GetDefaultView(this.Items).Refresh();

        int i = 0;
        dynamic dynJson = JsonConvert.DeserializeObject(e.Result);
        foreach (var item in dynJson)
        {
            String bodyText = "";
            bodyText += "Description:\n";
            bodyText += (String)item.description;

            this.Items.Add(new ItemViewModel()
            {
                ID = i.ToString(),
                AppID = "lc-details-001",
                Title = (String)item.title,
                SenderID = "",
                SenderName = "",
                Time = "",
                Type = "information",
                Body = bodyText,
                ValidTill = "",
                Subtitle = (String)item.subtitle,
                Icon = "",
                Image = "",
                ResponseURL = "",
                ResponseOptions = ""
            });

            i++;
        }
        this.IsDataLoaded = true;
    }
}

那么如何更新ObservableCollection？

Answer 1

好的数据不更新的原因是您将可观察集合设置为新实例。将LoadData函数更新为：

    public void LoadData()
    {
        if( IsDataLoaded )
            this.Items.Clear();

        WebClient webClient = new WebClient();
        webClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(webClient_DownloadStringCompleted);
        webClient.DownloadStringAsync(new System.Uri("http://questoons.com/"));                     
    }

如果您更新了收藏集的实例，则必须使用RaisePropertyChanged通知用户界面。

Answer 2

您需要将DeserializeObject转换为ItemViewModel
循环通过对象
将其添加到Items中。例如：Items.Add（obj）;
您需要根据Web服务响应创建ItemViewModel，您可以试试这个http://json2csharp.com/这将为您提供C＃对象

像这样：

else
{

    int i = 0;

    var dynJson = JsonConvert.DeserializeObject<ItemViewModel>(e.Result);
    foreach (var item in dynJson)
    {
        String bodyText = "";
        bodyText += "Description:\n";
        bodyText += (String)item.description;

        this.Items.Add(item);


        i++;
    }
    this.IsDataLoaded = true;
}

ObservableCollection不刷新

2 个答案: