Question

我正在开发一个Windows Phone应用程序。我有一个ListBox，从JSON文件填充。

这个JSON文件，我来自Web服务器。当我将我的应用程序与服务器同步时，ListBox不会自动填充（为空）。需要退出应用程序并返回ListBox显示数据。

所以，我还没有找到一种在运行时“刷新”我的ListBox的方法。

同步按钮：

        private void sinc(object sender, EventArgs e)
    {

        IsolatedStorageSettings iso = IsolatedStorageSettings.ApplicationSettings;

        if (iso.TryGetValue<string>("isoServer", out retornaNome))
        {
            serv = retornaNome;


            client = new WebClient();
            url = serv + "/json.html";
            Uri uri = new Uri(url, UriKind.RelativeOrAbsolute);
            client.OpenReadCompleted += new OpenReadCompletedEventHandler(client_OpenReadCompleted);
            client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(client_DownloadProgressChanged);
            client.OpenReadAsync(uri);
        }

        else
        {
            MessageBox.Show("Configure um servidor antes de sincronizar os dados!");
            NavigationService.Navigate(new Uri("/Page1.xaml", UriKind.RelativeOrAbsolute));

        }
    }

解析JSON：

            try
        {
            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            using (var readStream = new IsolatedStorageFileStream("json.html", FileMode.Open, FileAccess.Read, FileShare.Read, store))
            using (var reader = new StreamReader(readStream))
            {
                text = reader.ReadToEnd();
            }
            {


                DataContext = this;

                // String JSON
                string json = text;

                // Parse JObject
                JArray jObj = JArray.Parse(json);

                Items = new ObservableCollection<Fields>(
     jObj.Children().Select(jo => jo["result"]["fields"].ToObject<Fields>()));

            }


        }
        catch (Exception)
        {
            MessageBox.Show("A lista de produtos será exibida somente após a sincronização dos dados!");

        }

public ObservableCollection<Fields> Items { get; set; }

    public class Fields
    {

        [JsonProperty(PropertyName = "FId")]
        public int FId { get; set; }

        public string FNome { get; set; }
        public float FEstado1 { get; set; }
        public string FPais { get; set; }
        public string Quantity { get; set; }
        public string lero { get; set; }
        public string Quantity1 { get; set; }
        public string FEstado { get; set; }

    }

ListBox XAML：

 <ListBox Name="List1" ItemsSource="{Binding Items}" Margin="0,85,0,0" >
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="242" />
                                    <ColumnDefinition Width="128" />
                                    <ColumnDefinition Width="Auto" />
                                </Grid.ColumnDefinitions>
                                <StackPanel Hold="holdListAdd" Margin="0,0,-62,17" Grid.ColumnSpan="3">
                                    <StackPanel.Background>
                                        <SolidColorBrush Color="#FF858585" Opacity="0.5"/>
                                    </StackPanel.Background>
                                    <TextBlock x:Name="NameTxt" Grid.Column="0" Text="{Binding FNome}" TextWrapping="Wrap" FontSize="40" Style="{StaticResource PhoneTextExtraLargeStyle}"/>
                                    <TextBlock Grid.Column="1" Text="{Binding FEstado}" TextWrapping="Wrap" Margin="45,-6,12,0" Style="{StaticResource PhoneTextSubtleStyle}"/>

                                </StackPanel>
                                <TextBlock Grid.Column="0" Text="R$" Margin="15,48,158,17" Style="{StaticResource PhoneTextSubtleStyle}"/>
                            </Grid>
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                    <ListBox.ItemContainerStyle>
                        <Style TargetType="ListBoxItem">
                            <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
                        </Style>
                    </ListBox.ItemContainerStyle>
                </ListBox>

Answer 1

看看这两行：

public ObservableCollection<Fields> Items { get; set; }

Items = new ObservableCollection<Fields>(
     jObj.Children().Select(jo => jo["result"]["fields"].ToObject<Fields>()));

由于您要更改Items属性值，您应该以这种方式通知视图：

public ObservableCollection<Fields> Items 
{ 
    get { return items; } 
    set
    {
        if (items != value)
        {
            items = value;
            OnPropertyChanged("Items");
        }
    } 
}
private ObservableCollection<Fields> items;

或者（如果您不想更改属性声明）：

Items = new ObservableCollection<Fields>(/* fill the collection */);
OnPropertyChanged("Items"); // this is enough for the view to re-read property value

另一种做你想做的事情的方法，不是改变属性值，而是改变它的内容。这假设已经创建了Items集合，您只需为从服务器加载的每个结果调用Clear然后Add：

public ObservableCollection<Fields> Items
{
    get
    {
        return items ?? (items = new ObservableCollection<Fields>());
    }
}
private ObservableCollection<Fields> items;

var newItems = jObj.Children().Select(jo => jo["result"]["fields"].ToObject<Fields>());
Items.Clear();
foreach (var item in newItems)
{
    Items.Add(item);
}

如何在运行时刷新ListBox？

1 个答案: