Question

我有一个WPF应用程序用于播放视频，然后导航到另一个屏幕。应用程序首先播放视频，导航到page2.xaml并再次导航到视频页面我得到以下异常。

我的xaml看起来像这样：

<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Name="MainGrid">     
  <ContentControl x:Name="cntctrl" Content="{Binding VlcObject}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
</Grid>

VlcObject是Vlc.DotNet.Wpf.VlcControl的一个实例，我注意到VlcObject.MediaPlayer正在导航到第二页。因此，在导航到视频页面时，我正在创建一个VlcObject的新实例。我的ViewModel看起来像这样：

    private Vlc.DotNet.Wpf.VlcControl _vlcObject = null;
    public Vlc.DotNet.Wpf.VlcControl VlcObject
    {
        get { return _vlcObject; }
        set { Set(nameof(VlcObject), ref _vlcObject, value); }
    }
    private void InitialiseVLC()
    {
        if (VlcObject == null || VlcObject.MediaPlayer.IsDisposed)
        {
            DispatcherHelper.CheckBeginInvokeOnUI(() =>
            {
                VlcObject = null;
                VlcObject = new Vlc.DotNet.Wpf.VlcControl();
                VlcObject.MediaPlayer.VlcLibDirectoryNeeded += MediaPlayer_VlcLibDirectoryNeeded;
                VlcObject.MediaPlayer.EndInit();
                VlcObject.MediaPlayer.Opening += MediaPlayer_Opening;
                VlcObject.MediaPlayer.EndReached += MediaPlayer_EndReached;
                VlcObject.MediaPlayer.EncounteredError += MediaPlayer_EncounteredError;
                VlcObject.MediaPlayer.Disposed += MediaPlayer_Disposed;
            });
        }
    }
    private void MediaPlayer_Disposed(object sender, EventArgs e)
    {
        Logger.LogInfo("Media Player is disposed.");
        DispatcherHelper.CheckBeginInvokeOnUI(() =>
        {
            try
            {
                VlcObject.MediaPlayer.VlcLibDirectoryNeeded -= MediaPlayer_VlcLibDirectoryNeeded;
                VlcObject.MediaPlayer.Opening -= MediaPlayer_Opening;
                VlcObject.MediaPlayer.EndReached -= MediaPlayer_EndReached;
                VlcObject.MediaPlayer.EncounteredError -= MediaPlayer_EncounteredError;
                VlcObject.MediaPlayer.Disposed -= MediaPlayer_Disposed;
                //VlcObject = null;

            }
            catch (Exception ex)
            {
                Logger.LogError("Error while disposing MediaPlayer: ");
                Logger.LogError(ex);
            }
        });
    }
    public void OnNavigatedTo(object parameter, bool isBack = false)
    {            
            InitializeVLC();
    }

以下是我得到的例外情况：

System.Windows.Markup.XamlParseException：设置属性＆＃39; System.Windows.Controls.ContentControl.Content＆＃39;抛出一个例外。   ---＆GT; System.InvalidOperationException：指定的元素已经是另一个元素的逻辑子元素。首先断开它。在   System.Windows.FrameworkElement.ChangeLogicalParent（DependencyObject的   newParent）at   System.Windows.FrameworkElement.AddLogicalChild（Object child）at   System.Windows.Controls.ContentControl.OnContentChanged（对象   oldContent，Object newContent）at   System.Windows.Controls.ContentControl.OnContentChanged（DependencyObject的   d，DependencyPropertyChangedEventArgs e）at   System.Windows.DependencyObject.OnPropertyChanged（DependencyPropertyChangedEventArgs   吃   System.Windows.FrameworkElement.OnPropertyChanged（DependencyPropertyChangedEventArgs   吃   System.Windows.DependencyObject.NotifyPropertyChange（DependencyPropertyChangedEventArgs   args）at   System.Windows.DependencyObject.UpdateEffectiveValue（EntryIndex   entryIndex，DependencyProperty dp，PropertyMetadata元数据，   EffectiveValueEntry oldEntry，EffectiveValueEntry＆amp; newEntry，布尔值   coerceWithDeferredReference，Boolean coerceWithCurrentValue，   OperationType operationType）at   System.Windows.DependencyObject.SetValueCommon（DependencyProperty dp，   对象值，PropertyMetadata元数据，布尔值   coerceWithDeferredReference，Boolean coerceWithCurrentValue，   OperationType operationType，Boolean isInternal）at   System.Windows.Baml2006.WpfKnownMemberInvoker.SetValue（对象   实例，对象值）at   MS.Internal.Xaml.Runtime.ClrObjectRuntime.SetValue（XamlMember成员，   对象obj，对象值）at   MS.Internal.Xaml.Runtime.ClrObjectRuntime.SetValue（Object inst，   XamlMember属性，Object value）---内部异常堆栈的结束   追踪--- at   System.Windows.Markup.XamlReader.RewrapException（Exception e，   IXamlLineInfo lineInfo，Uri baseUri）at   System.Windows.Markup.WpfXamlLoader.Load（XamlReader xamlReader，   IXamlObjectWriterFactory writerFactory，Boolean   skipJournaledProperties，Object rootObject，XamlObjectWriterSettings   设置，Uri baseUri）at   System.Windows.Markup.WpfXamlLoader.LoadBaml（XamlReader xamlReader，   Boolean skipJournaledProperties，Object rootObject，XamlAccessLevel   accessLevel，Uri baseUri）at   System.Windows.Markup.XamlReader.LoadBaml（Stream stream，ParserContext   parserContext，Object parent，Boolean closeStream）at   System.Windows.Application.LoadBamlStreamWithSyncInfo（Stream stream，   ParserContext pc）at   MS.Internal.AppModel.AppModelKnownContentFactory.BamlConverter（流   stream，Uri baseUri，Boolean canUseTopLevelBrowser，Boolean   sandboxExternalContent，Boolean allowAsync，Boolean   isJournalNavigation，XamlReader＆amp; asyncObjectConverter）at   MS.Internal.AppModel.MimeObjectFactory.GetObjectAndCloseStream（流   s，ContentType contentType，Uri baseUri，Boolean   canUseTopLevelBrowser，Boolean sandboxExternalContent，Boolean   allowAsync，Boolean isJournalNavigation，XamlReader＆amp;   asyncObjectConverter）at   System.Windows.Navigation.NavigationService.GetObjectFromResponse（WebRequest的   请求，WebResponse响应，Uri destinationUri，对象navState）
  在System.Windows.Navigation.NavigationService.DoNavigate（Uri source，   NavigationMode f，Object navState）at   System.Windows.Navigation.NavigateQueueItem.Dispatch（Object obj）at   System.Windows.Threading.ExceptionWrapper.InternalRealCall（代表   回调，对象args，Int32 numArgs）at   MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen（对象   source，Delegate方法，Object args，Int32 numArgs，Delegate   catchHandler）

有人可以帮助我。

Answer 1

“先断开连接”。错误信息的一部分是关键。由于您绑定了内容，因此它听起来像是在另一个控件（或页面）上激活相同的绑定。您应该尝试确保内容不绑定到多个控件。页面是否共享相同的视图模型？您可以尝试为每个页面创建一个唯一的视图模型，并为每个视图模型提供唯一的内容包装。

Answer 2

以下给出的链接正在解决相同的问题。一旦你得到暗示，就去吧。

Specified element is already the logical child of another element. Disconnect it first

wpf＆＃39; System.Windows.Controls.ContentControl.Content＆＃39;抛出一个例外。指定的元素已经是另一个元素

2 个答案: