ItemTemplateSelector之间的列表框更改

Question

我ListBox中的Application ItemTemplateSelector设有TemplateSelector templateSelector = new TemplateSelector(); templateSelector.SongTemplate = Resources["Template"] as DataTemplate; templateSelector.SongTemplateCached = Resources["TemplateCached"] as DataTemplate; HistoryList.ItemTemplateSelector = templateSelector; ：

    ObservableCollection<SongItem> songlist;

    public const int MAX_RECENT = 10000;

    public HistoryViewModel()
    {
        NotificationCenterManager.Instance.AddObserver(UpdateCache, AppConst.UPDATECACH);

        List<SongItem> tmpArr = SqlLiteManager.CreateInstance().LoadHistoryFromDatabase();

        songList = new ObservableCollection<SongItem>(tmpArr);
    }

    public ObservableCollection<SongItem> SongList
    {
        get { return songlist; }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;
    private void RaisePropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
    }

    private void UpdateCache(Notification p_notification)
    {
        RaisePropertyChanged("SomeName");
    }

他们之间的不同之处在于，如果这首歌是下载或不下载的话。

这是列表框的ViewModel：

UpdateCache

当歌曲完成下载时，会调用<ListBox ItemsSource="{Binding Path=VideoList}" Name="HistoryList" Style="{StaticResource myListboxStyle}" BorderThickness="0" Template="{DynamicResource ListViewNewTemplate}" Margin="-2,0,0,0" MouseDoubleClick="Mouse_Double_Click" ScrollViewer.CanContentScroll="False"> <ListBox.Resources> <!--Defines a context menu--> <ContextMenu x:Key="MyElementMenu"> <MenuItem Header="Delete from history" Click="MenuItemDelete_Click"/> </ContextMenu> <!--Sets a context menu for each ListBoxItem in the current ListBox--> <Style TargetType="{x:Type ListBoxItem}"> <Setter Property="ContextMenu" Value="{StaticResource MyElementMenu}"/> </Style> </ListBox.Resources> </ListBox> 方法，但ListBox不会更新（将设计从SongTemplate模式更改为SongTemplateCached）

我如何解决它？

修改

XAML：

        public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        string filePath = ApplicationDataPaths.GetRootDataPath() + "\\www\\CachedContent\\";

            string file = video.VideoId + "*.mp4";

            string[] listfiles = System.IO.Directory.GetFiles(filePath, file, System.IO.SearchOption.TopDirectoryOnly);
            if (listfiles.Length > 0)
            {
                return VideoTemplateCached;
            }
            else
            {
                return VideoTemplate;
            }
    }

选择器：

{{1}}

Answer 1

您更改了Song-Item的属性，但是您已经绑定了包含Song-Item的Collection。除非您在更改项目时提出CollectionChangedEvent，否则不会通知它更新UI。

我猜您必须实施ObservableCollection and Item PropertyChanged之类的通知才能更新用户界面。