（WPF / C＃）使用DispatcherTimer进行UI更新循环

Question

I have an application where I have a View with several interactive UI elements. In addition, I have a DispatcherTimer running updates to the UI every 10 seconds. I have made a custom dynamic grid that arranges the child elements differently based on how many children the dynamic grid has.

However, I have an issue. When the timer fires the Dynamic Grid get stuck in a loop when updating the elements, and I am not sure why. Here is a simplified version of the code, be sure to tell me if it is insufficient:

MainWindow.xaml.cs

    public MainWindow()
    {
        InitializeComponent();

        main = new MainView(pollCollectionMain);


        RefreshTimer = new DispatcherTimer();
        RefreshTimer.Tick += new EventHandler(OnTimedEvent);
        RefreshTimer.Interval = new TimeSpan(0, 0, 10);
        RefreshTimer.Start();

    }

    private void OnTimedEvent(object sender, EventArgs e)
    {   
        //The Polling class has a variable output
        pollObj = new Polling();
        pollCollectionMain = pollObj.PollingCollection;
        main = new MainView(pollCollectionMain);
    }

main.cs

    public MainView(ObservableCollection<PollingData> pollLocal)
    {
        dynGrid = new DynamicGrid();
        p = pollLocal;

        for (int i = 0; i < p.Count; i++)
        {
            //Making some new controls
            //ControlGrid is just a Grid with mouse functionality
            mainControlGrid = new ControlGrid();
            mainControlGrid.Children.Add(someControl);
            dynGrid.Children.Add(mainControlGrid);
        }

    }

DynamicGrid(), where an infinite loop happens

    public DynamicGrid()
    {

        _currentChildrenCount = 0;

        //The following is the infinite loop
        LayoutUpdated += (s, e) =>
        {
            if (Children?.Count != _currentChildrenCount)
            {
                _currentChildrenCount = (Children != null) ? Children.Count : 0;
                OnNumberOfItemsChangedImpl();
            }
        };
    }

Answer 1

You should not manage layout like this in WPF. WPF has a built-in way of managing this: Using a Panel.

public class YourPanel : Panel {

    protected override Size MeasureOverride(Size availableSize) {
        if (InternalChildren.Count == 0) return new Size(0, 0);
        //Measure each children's size and then compute and return the size the panel needs to display correctly

        foreach(UIElement children in InternalChildren) {
            children.Measure(sizeYouWantToGiveToTheElement);
        }

        return totalSizeYourPanelNeeds;
    }

    protected override Size ArrangeOverride(Size finalSize) {
        if (InternalChildren.Count == 0) return new Size(0, 0);

        //Arrange each element in the panel according to your own rules
        for (int i = 0; i < InternalChildren.Count; i++) {
            UIElement children = InternalChildren[i];

            //Arrange the panel's children at the position you want and with the size you want
            children.Arrange(new Rect(childrenPosition, childrenSize));
        }

        return finalSize;
    }
}

Unless you do this, you'll make needless updates and disturb the dispatcher.

You can the use your panel in an ItemsControl:

<ItemsControl ItemsSource="{Binding Path=YourItems, Mode=OneWay}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <YourPanel/>
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
</ItemsControl>

You can find more information on custom panels here or here for example.