Windows Phone:ListBox 无法显示添加的项目
本文关键字:显示 添加 项目 Phone ListBox Windows | 更新日期: 2023-09-27 18:34:04
我正在尝试在 ObservableCollection 中显示添加的元素,以显示在页面 (MenuPage( 中的列表框上。
此集合由另一个页面提供,称为 AddActivityAdvancedPage。在AddActivityAdvancedPage中,用户填写表单并将我将其作为对象(pmaActivity(发送的信息保存到MenuPage。MenuPage 接收对象并添加到 ObservableCollection 上。
问题是我的可观察集合没有保存添加的它!itens 不会显示在列表框中。
我调试代码,每次应用程序点击菜单页面上ListActivitiesAdvanced.Add(pmaActivity);
行时,ListActivitiesAdvanced 都是空的。我需要以某种方式将ListActivitiesAdvanced设置为静态,但我不知道如何正确执行此操作。
添加活动高级页面类:
public partial class AddActivityAdvancedPage : PhoneApplicationPage
{
//method called to pass the object pmaActivity as parameter to the MenuPage
private void btnSave_Click(object sender, EventArgs e)
{
Dispatcher.BeginInvoke(() =>
{
PhoneApplicationService.Current.State.Remove("pmaActivity");
PhoneApplicationService.Current.State["pmaActivity"] = pmaActivity;
NavigationService.Navigate(new Uri("/MenuPage.xaml", UriKind.Relative));
});
}
}
菜单页面类:
public partial class MenuPage : PhoneApplicationPage
{
public ObservableCollection<PmaActivity> ListActivitiesAdvanced { get; set; }
public MenuPage()
{
InitializeComponent();
ListActivitiesAdvanced = new ObservableCollection<PmaActivity>();
}
//Method called to receive the pmaActivity and add in the collection
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (PhoneApplicationService.Current.State.ContainsKey("pmaActivity"))
{
PmaActivity pmaActivity = PhoneApplicationService.Current.State["pmaActivity"] as PmaActivity;
PhoneApplicationService.Current.State.Remove("pmaActivity");
ListActivitiesAdvanced.Add(pmaActivity);
}
}
}
菜单页中的列表框:
<ListBox ItemsSource="{Binding ListActivitiesAdvanced}" Margin="0,0,12,0">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Height="105" >
<Border BorderThickness="1" Width="73" Height="73" BorderBrush="#FF005DFF" Background="#FF005DFF" Margin="0,10,8,0" VerticalAlignment="Top"/>
<StackPanel Width="370">
<TextBlock Text="{Binding clientName}" TextWrapping="NoWrap"
Margin="12,0,0,0" Style="{StaticResource PhoneTextLargeStyle}"/>
<TextBlock Text="{Binding projectName}" TextWrapping="NoWrap"
Margin="12,-6,0,0" Style="{StaticResource PhoneTextSubtleStyle}"/>
</StackPanel>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
我尝试从 MenuPage 中删除 ListActivitiesAdvanced,并将 x:Name 添加到具有相同名称的 ListBox 元素:ListActivitiesAdvanced:
<ListBox x:Name="ListActivitiesAdvanced" Margin="0,0,12,0"/>
但在这种情况下,问题是这个列表没有保存之前添加的itens!每次我添加一个项目时,只有最后添加的项目会显示在可观察集合中。
感谢您的任何帮助!我真的有问题,有很多方法可以在ListBox中绑定列表(如StaticResource,Source,Binding,List,ObservableCollection,IEnumerable...(,我无法理解所有的差异。
如果要保留项目列表,那么为什么不将完整列表放入应用程序状态呢?
//method called to pass the object pmaActivity as parameter to the MenuPage
private void btnSave_Click(object sender, EventArgs e)
{
Dispatcher.BeginInvoke(() =>
{
List<PmaActivity> activities;
if (PhoneApplicationService.Current.State.ContainsKey("pmaActivities"))
activities = PhoneApplicationService.Current.State["pmaActivities"];
else
activities = new List<PmaActivity>();
activities.Add(pmaActivity);
PhoneApplicationService.Current.State["pmaActivities"] = pmaActivities;
NavigationService.Navigate(new Uri("/MenuPage.xaml", UriKind.Relative));
});
}
然后在主页中,从列表中填充:
//Method called to receive the pmaActivity and add in the collection
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (PhoneApplicationService.Current.State.ContainsKey("pmaActivity"))
{
if (PhoneApplicationService.Current.State.ContainsKey("pmaActivities"))
{
var pmaActivities = PhoneApplicationService.Current.State["pmaActivities"] as List<PmaActivity>;
foreach (var activity in pmaActivities)
ListActivitiesAdvanced.Add(activity);
}
}