如何在 UI 线程中工作时更新进度条

我有一个ProgressBar和一个TreeView。

我用一堆数据填充了TreeView，一旦应用了它，我就会运行TreeView的visual tree，基本上迫使它生成每个TreeViewItems。我希望ProgressBar说明这项工作是如何进展的。

这是我为创建TreeViewItems而运行的行为代码。一旦属性设置为 true ItemsLoaded它就会开始处理项目。它反过来更新单一实例类中的属性以更新进度。

public class TreeViewBehaviors
{
    public static readonly DependencyProperty ItemsLoadedProperty =
        DependencyProperty.RegisterAttached("ItemsLoaded", typeof(bool), typeof(TreeViewBehaviors),
        new FrameworkPropertyMetadata(false, new PropertyChangedCallback(OnItemsLoadedPropertyChanged)));
    public static bool GetItemsLoaded(DependencyObject obj)
    {
        return (bool)obj.GetValue(ItemsLoadedProperty);
    }
    public static void SetItemsLoaded(DependencyObject obj, bool value)
    {
        obj.SetValue(ItemsLoadedProperty, value);
    }
    private static void OnItemsLoadedPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        if ((bool)e.NewValue)
        {
            GetTotalNTreeViewItems((TreeView)sender, sender);
        }
    }
    public static readonly DependencyProperty NodesProcessedProperty =
        DependencyProperty.RegisterAttached("NodesProcessed", typeof(int), typeof(TreeViewBehaviors),
        new FrameworkPropertyMetadata(default(int), new PropertyChangedCallback(OnNodesProcessedPropertyChanged)));
    public static int GetNodesProcessed(DependencyObject obj)
    {
        return (int)obj.GetValue(NodesProcessedProperty);
    }
    public static void SetNodesProcessed(DependencyObject obj, int value)
    {
        if (GetNodesProcessed(obj) != value)
        {
            obj.SetValue(NodesProcessedProperty, value);
        }
    }
    private static void OnNodesProcessedPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        if (e.NewValue != null)
        {
            double trouble = Math.Round(((GetProgressMaximum(sender) / GetTotalNodesToProcess(sender)) * (int)e.NewValue), 1);
            TreeViewSingletonClass.Instance.DisplayProgress = trouble;
        }
    }
    public static readonly DependencyProperty TotalNodesToProcessProperty =
        DependencyProperty.RegisterAttached("TotalNodesToProcess", typeof(double), typeof(TreeViewBehaviors),
        new FrameworkPropertyMetadata(default(double)));
    public static double GetTotalNodesToProcess(DependencyObject obj)
    {
        return (double)obj.GetValue(TotalNodesToProcessProperty);
    }
    public static void SetTotalNodesToProcess(DependencyObject obj, double value)
    {
        obj.SetValue(TotalNodesToProcessProperty, value);
    }

    public static readonly DependencyProperty ProgressMaximumProperty =
        DependencyProperty.RegisterAttached("ProgressMaximum", typeof(double), typeof(TreeViewBehaviors),
        new FrameworkPropertyMetadata(default(double)));
    public static double GetProgressMaximum(DependencyObject obj)
    {
        return (double)obj.GetValue(ProgressMaximumProperty);
    }
    public static void SetProgressMaximum(DependencyObject obj, double value)
    {
        obj.SetValue(ProgressMaximumProperty, value);
    }
    private static void GetTotalNTreeViewItems(ItemsControl container, DependencyObject sender)
    {
        if (container != null)
        {
            container.ApplyTemplate();
            ItemsPresenter itemsPresenter = (ItemsPresenter)container.Template.FindName("ItemsHost", container);
            if (itemsPresenter != null)
            {
                itemsPresenter.ApplyTemplate();
            }
            else
            {
                // The Tree template has not named the ItemsPresenter, 
                // so walk the descendents and find the child.
                itemsPresenter = FindVisualChild<ItemsPresenter>(container);
                if (itemsPresenter == null)
                {
                    container.UpdateLayout();
                    itemsPresenter = FindVisualChild<ItemsPresenter>(container);
                }
            }
            Panel itemsHostPanel = (Panel)VisualTreeHelper.GetChild(itemsPresenter, 0);
            // Ensure that the generator for this panel has been created.
            UIElementCollection children = itemsHostPanel.Children;
            for (int i = 0, count = container.Items.Count; i < count; i++)
            {
                TreeViewItem subContainer = (TreeViewItem)container.ItemContainerGenerator.ContainerFromIndex(i);
                GetTotalNTreeViewItems(subContainer, sender);
                SetNodesProcessed(sender, GetNodesProcessed(sender) + 1);
            }
        }
    }
    private static T FindVisualChild<T>(Visual visual) where T : Visual
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(visual); i++)
        {
            Visual child = (Visual)VisualTreeHelper.GetChild(visual, i);
            if (child != null)
            {
                T correctlyTyped = child as T;
                if (correctlyTyped != null)
                    return correctlyTyped;
                T descendent = FindVisualChild<T>(child);
                if (descendent != null)
                    return descendent;
            }
        }
        return null;
    }
}

单例类

public class TreeViewSingletonClass : INotifyPropertyChanged
{
    private static double m_DisplayProgress = 0;
    public double DisplayProgress
    {
        get { return m_DisplayProgress; }
        set
        {
            if (m_DisplayProgress == value)
                return;
            m_DisplayProgress = value;
            NotifyPropertyChanged();
        }
    }
    private static TreeViewSingletonClass m_Instance;
    public static TreeViewSingletonClass Instance
    {
        get
        {
            if (m_Instance == null)
                m_Instance = new TreeViewSingletonClass();
            return m_Instance;
        }
    }
    private TreeViewSingletonClass(){}
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

XAML：

<ProgressBar Grid.Column="2" Grid.Row="1" Margin="5" 
             Width="20" Height="150" 
             VerticalAlignment="Top" 
             Value="{Binding Source={x:Static helpers:TreeViewSingletonClass.Instance}, Path=DisplayProgress}" 
             Maximum="{Binding ProgressMaximum}"  />

我的问题是，每件事都在正确处理，只是ProgressBar直到最后才更新。我意识到两者都在同一个UI thread上内联工作，所以这将是问题所在。

所以我的问题，这两个都在同一个线程上工作，我怎样才能更新这个ProgressBar。

[编辑]

这个WPF是一个WinForm ElementHost中的UserControl，我只是将以下内容放入WinForm中，以便我可以访问Application.Current

if ( null == System.Windows.Application.Current )
{
   new System.Windows.Application();
}

在尝试实现 Xavier 的第二个建议后：将工作拆分为更小的部分，并使用 BeginInvoke 与调度程序单独排队（例如，将循环的主体转换为调度程序调用）

所以在for循环中，我卡了以下内容：

for (int i = 0, count = container.Items.Count; i < count; i++)
{
    Application.Current.Dispatcher.BeginInvoke(new Action(delegate()
    {
        TreeViewItem subContainer = (TreeViewItem)container.ItemContainerGenerator.ContainerFromIndex(i);
        GetTotalNTreeViewItems(subContainer, sender);
        SetNodesProcessed(sender, GetNodesProcessed(sender) + 1); 
    }));
}

不幸的是，这没有奏效，一定是做错了什么。

Dispatcher.BeginInvoke(new Action(delegate() { mProgress.Value += 1.0; }));