如何在运行时刷新ListBox

本文关键字：刷新 ListBox 运行时 | 更新日期: 2023-09-27 18:25:22

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

这个JSON文件，我从Web服务器上得到。当我将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到ListBox显示数据。

因此，我还没有找到在运行时"刷新"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>

如何在运行时刷新ListBox

看看这两行：

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

由于您正在更改Items属性值，因此应通过以下方式通知视图：

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

或者这个（如果你不想更改属性声明）：

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

另一种方法是不更改属性值，而是更改其内容。这假设Items集合已经创建，您只需为每个结果调用Clear，然后调用Add，这些结果是从服务器加载的：

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);
}
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