UniformGrid 和 ItemsSource

Question

我有一个UniformGrid。在里面，我想放一个 Grid，其中包含 2 个 children - 和 Image 以及一个 Canvas。我已经有一个 List<Grid> 成员，其中包含具有该定义的 Grid。

我正在将 Image 的来源从 null 更新为实际图像，希望图像显示在 UniformGrid 中，但没有任何反应。

这是我的代码：

Xaml:

<Border Grid.Row="0" >
        <ItemsControl x:Name="StreamsItemsControl" ItemsSource="{Binding Streams}">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <UniformGrid x:Name="StreamsGrid"  ClipToBounds="True" Height="300" />
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
        </ItemsControl>
    </Border>

ViewModel:

private List<Grid> m_streams = new List<Grid>();
public List<Grid> Streams
        {
            get { return m_streams; }
            set
            {
                m_streams = value;
                OnPropertyChanged("Streams");
            }
        }

编辑：添加更多代码：

    public struct StreamContainer
    {
        public string StreamName;
        public Grid StreamGrid;
        public Canvas StreamCanvas;
        public Image StreamImage;
    }
    private readonly List<StreamContainer> m_streamsContainer = new List<StreamContainer>();

    public SequencesPlayerViewModel()
    {
        RegisterStream("Color");
        RegisterStream("Depth");
        RegisterStream("Ir");
        RegisterStream("Left");
    }

    private void RegisterStream(string streamName)
    {
        StreamContainer streamContainer;

        streamContainer.StreamName = streamName;
        streamContainer.StreamCanvas = new Canvas { Name = streamName + "Canvas", Background = Brushes.Transparent, VerticalAlignment = VerticalAlignment.Top };
        streamContainer.StreamImage = new Image { Name = streamName + "Image", Stretch = Stretch.Uniform, VerticalAlignment = VerticalAlignment.Top };

        var widthBinding = new Binding { Path = new PropertyPath("ActualWidth") };
        var heightBinding = new Binding
        {
            Path = new PropertyPath("ActualHeight"),
            Source = streamContainer.StreamImage
        };


        streamContainer.StreamCanvas.SetBinding(FrameworkElement.HeightProperty, heightBinding);
        streamContainer.StreamCanvas.SetBinding(FrameworkElement.WidthProperty, widthBinding);

        streamContainer.StreamGrid = new Grid { Name = streamName + "Grid" };
        streamContainer.StreamGrid.Children.Add(streamContainer.StreamImage);
        streamContainer.StreamGrid.Children.Add(streamContainer.StreamCanvas);

        streamContainer.StreamGrid.Visibility = Visibility.Collapsed;

        m_streamsContainer.Add(streamContainer);
    }

    private void AddStream(StreamContainer currentStream)
    {
        var listOfStreams = GetListOfStream();

        if (listOfStreams.Count > 0)
        {
            var streamToAdd = listOfStreams.Find(currStream => currStream.Name == currentStream.StreamName);
            if (streamToAdd != null)
                if (!String.IsNullOrEmpty(currentStream.StreamName))
                {
                    currentStream.StreamGrid.Visibility = Visibility.Visible;
                    (currentStream.StreamGrid.Children[0] as Image).Source = streamToAdd.ImageBitmap;
                }
        }

        Streams.Add(currentStream.StreamGrid);
    }

    private void OnNewFrameReady(uint frameNumber)
    {
        try
        {
            var listOfStreams = GetListOfStream();

            foreach (var elem in Streams)
            {
                var currentCanvas = (elem.Children[1] as Canvas);
                var canvasName = currentCanvas.Name.Split(new[] { "Canvas" }, StringSplitOptions.RemoveEmptyEntries).First();

                var currentStream = listOfStreams.Find(currStream => currStream.Name == canvasName);
                if (!String.IsNullOrEmpty(currentStream.Name))
                    (elem.Children[0] as Image).Source = currentStream.ImageBitmap;
                Panel p = currentCanvas;
                elem.UpdateLayout();

                elem.Width = (elem.Children[0] as Image).ActualWidth;
                elem.Height = (elem.Children[0] as Image).ActualHeight;
                elem.UpdateLayout();
            }
        }
        catch (Exception ex)
        {
        }
    }

ViewModel连接正确，其他控件Bindings工作正常

我还可以看到 Streams 成员已正确更新，这意味着 Image 已使用新的 Source.

正确更新

我错过了什么？

Answer 1

可能问题是您的项目根本没有显示 -- 不是图像没有更新（因为我看到您正在更新源属性直接图像元素）...使用列表，PropertyChanged 事件只会在 List<> 更改时触发，而不是在向其中添加内容时触发，这与 ObservableCollection<> 当项目为 added/removed/replaced/cleared.

时触发事件

尝试将 List<> 替换为 ObservableCollection<>（在 System.Collections.ObjectModel 中找到）

除此之外，Grid 和 Image 可以在 ItemsControl.ItemTemplate 中的 DataTemplate 中定义，Source 绑定到属性的 stream ViewModel（这是你应该收集的）——但与问题无关。

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