以编程方式使用自定义元素创建网格

Question

我正在尝试以编程方式创建一个网格，并将自定义控件作为子控件附加到网格中，作为 2x2 矩阵中的第 0 行第 0 列。为了让事情变得更棘手，我使用了 MVVM 设计模式。这里有一些代码可以帮助大家理解这个想法：

App.xaml.cs

base.OnStartup(e);
var viewModel = new MainWindowViewModel();
var mainWindow = new MainWindow();
mainWindow.GridWindows = viewModel.Window.GridWindows;

MainWindowViewModel - 方法返回 GridWindows。

    private Grid CreateGrid()
    {
        Grid grid = new Grid();

        // Create column definitions.
        ColumnDefinition columnDefinition1 = new ColumnDefinition();
        ColumnDefinition columnDefinition2 = new ColumnDefinition();
        columnDefinition1.Width = new GridLength(640);
        columnDefinition2.Width = new GridLength(640);

        // Create row definitions.
        RowDefinition rowDefinition1 = new RowDefinition();
        RowDefinition rowDefinition2 = new RowDefinition();
        rowDefinition1.Height = new GridLength(340);
        rowDefinition2.Height = new GridLength(340);

        // Attached definitions to grid.
        grid.ColumnDefinitions.Add(columnDefinition1);
        grid.ColumnDefinitions.Add(columnDefinition2);
        grid.RowDefinitions.Add(rowDefinition1);
        grid.RowDefinitions.Add(rowDefinition2);

        // Create preview window.
        Border border = new Border();
        border.BorderThickness = new Thickness(20);
        border.Padding = new Thickness(8);
        border.SetResourceReference(Control.BackgroundProperty, "PreviewWindow");

        MediaRTSPElement previewElement = new MediaRTSPElement();
        previewElement.Name = "RTSPStreamPlayer";
        previewElement.Stretch = Stretch.UniformToFill;
        previewElement.Source = "rtsp://192.100.100.22/media/video1";
        previewElement.VideoRenderer = VideoRendererType.EnhancedVideoRenderer;
        previewElement.LoadedBehavior = WPFEVR.DirectShow.Players.MediaState.Play;
        previewElement.SpeedRatio = 0.5;

        //border.Child = previewElement;

        // Add preview window.
        for (int i = 0; i < 4; i++)
        {
            grid.Children.Add(previewElement as UIElement);
            Grid.SetColumn(previewElement, i);
            Grid.SetRow(previewElement, i);
            break;
        }

        return grid;
    }

以及网格应分配给的 XAML 标记< /strong>

<Grid x:Name="GridWindows"></Grid>

问题是我的自定义控件没有出现在网格布局中，这是在没有代码隐藏的情况下执行此操作的 xaml 代码，并且这确实有效：

        <Grid x:Name="GridWindows">
            <!--<Grid.ColumnDefinitions>
                <ColumnDefinition Width="640" />
                <ColumnDefinition Width="640" />
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="340" />
                <RowDefinition Height="340" />
            </Grid.RowDefinitions>
            <Border BorderThickness="20" Padding="8" Background="{DynamicResource ResourceKey=PreviewWindow}" Grid.Row="0" Grid.Column="0">
                <evr:MediaRTSPElement x:Name="RTSPStreamPlayer"
                              Stretch="UniformToFill"
                              VideoRenderer="EnhancedVideoRenderer"
                              LoadedBehavior="Play"
                              Source="rtsp://192.100.100.22/media/video1"
                              SpeedRatio="0.5" />
            </Border>
            <Border BorderThickness="20" Padding="8" Background="{DynamicResource ResourceKey=PreviewWindow}" Grid.Row="0" Grid.Column="1">
                <evr:MediaRTSPElement x:Name="RTSPStreamPlayer2"
                              Stretch="UniformToFill"
                              VideoRenderer="EnhancedVideoRenderer"
                              LoadedBehavior="Play"
                              Source="rtsp://192.100.100.78/media/video1"
                              SpeedRatio="0.5" />
            </Border>
            <Border BorderThickness="20" Padding="8" Background="{DynamicResource ResourceKey=PreviewWindow}" Grid.Row="1" Grid.Column="0">
                <evr:MediaRTSPElement x:Name="RTSPStreamPlayer3"
                              Stretch="UniformToFill"
                              VideoRenderer="EnhancedVideoRenderer"
                              LoadedBehavior="Play"
                              Source="rtsp://192.100.100.78/media/video1"
                              SpeedRatio="0.5" />
            </Border>
            <Border BorderThickness="20" Padding="8" Background="{DynamicResource ResourceKey=PreviewWindow}" Grid.Row="1" Grid.Column="1">
                <evr:MediaRTSPElement x:Name="RTSPStreamPlayer4"
                              Stretch="UniformToFill"
                              VideoRenderer="EnhancedVideoRenderer"
                              LoadedBehavior="Play"
                              Source="rtsp://192.100.100.22/media/video1"
                              SpeedRatio="0.5" />
            </Border>-->
        </Grid>

关于为什么编程代码不起作用的任何想法？

Answer 1

如果您在 xaml 中创建Grid，则以后无法在代码中设置它。网格（实例）已经在 VisualTree 中。覆盖变量不会产生任何效果。您应该将 Grid 设置为 xaml 定义的控件的内容。我猜你的代码看起来像这样：

代码：

this.GridWindows = createdGrid;

Xaml：

<Grid x:Name="GridWindows"></Grid>

在代码中你应该有这样的东西：

this.GridWindows.Children.Add(createdGrid);