列表框在ItemTemplateSelector之间的更改

Question

我的Application中有Application，它是用ItemTemplateSelector设计的

TemplateSelector templateSelector = new TemplateSelector();

templateSelector.SongTemplate = Resources["Template"] as DataTemplate;
templateSelector.SongTemplateCached = Resources["TemplateCached"] as DataTemplate;

HistoryList.ItemTemplateSelector = templateSelector;

他们之间的不同之处在于，如果这首歌是下载的还是不下载的。

这是列表框的ViewModel：

    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");
    }

当歌曲完成下载时，将调用UpdateCache方法，但ListBox不会更新(将设计从SongTemplate模式更改为SongTemplateCached)

我怎么才能修好它？

编辑

XAML：

<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>

选择器：

        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;
            }
    }

Answer 1

您更改了歌曲项的属性，但是您已经绑定到包含歌曲项的集合。除非在更改项时引发CollectionChangedEvent，否则不会通知它更新UI。

我想您必须实现像ObservableCollection and Item PropertyChanged这样的通知才能更新UI。