WPF在单独的UI线程上加载动画？ （C＃）

Question

好的，我有一个加载动画，在填充大型DataTable时运行，让用户知道程序没有冻结。 我有动画工作正常，但它也冻结了DataTable也在更新。 有没有办法拥有多个UI线程，以便在DataTable加载信息时动画将继续运行？

编辑：当前代码如下。

private void CreateFileTable()
{
    file_data = new DataSet();
    data_table = new DataTable();
    file_data.Tables.Add(data_table);

    DataColumn tempCol = new DataColumn("File Name", typeof(string));
    data_table.Columns.Add(tempCol);

    tempCol = new DataColumn("Ext", typeof(string));
    data_table.Columns.Add(tempCol);

    tempCol = new DataColumn("Size", typeof(string));
    data_table.Columns.Add(tempCol);

    tempCol = new DataColumn("Created", typeof(Label));
    data_table.Columns.Add(tempCol);

    tempCol = new DataColumn("Modified", typeof(Label));
    data_table.Columns.Add(tempCol);

    tempCol = new DataColumn("Accessed", typeof(Label));
    data_table.Columns.Add(tempCol);

    tempCol = new DataColumn("Location", typeof(string));
    data_table.Columns.Add(tempCol);

    File_List.ItemsSource = file_data.Tables[0].DefaultView;
}

private void PopulateDirectories(string[] directories)
{
    for (int i = 0; i < directories.Length; i++)
    {
        DirectoryInfo tempDirInfo = new DirectoryInfo(directories[i]);

        bool isSystem = ((tempDirInfo.Attributes & FileAttributes.System) == FileAttributes.System);

        if (!isSystem)
        {
            DataRow tempRow = data_table.NewRow();
            tempRow["File Name"] = tempDirInfo.Name;
            tempRow["Ext"] = "";
            tempRow["Size"] = "";

            tempLabel = new Label();
            tempLabel.Padding = new Thickness(2, 0, 2, 0);
            tempLabel.Content = tempDirInfo.CreationTime.ToLongDateString() + ", " + tempDirInfo.CreationTime.ToLongTimeString();

            tempRow["Created"] = tempLabel;

            tempLabel = new Label();
            tempLabel.Padding = new Thickness(2, 0, 2, 0);
            tempLabel.Content = tempDirInfo.LastWriteTime.ToLongDateString() + ", " + tempDirInfo.LastWriteTime.ToLongTimeString();

            tempRow["Modified"] = tempLabel;

            tempLabel = new Label();
            tempLabel.Padding = new Thickness(2, 0, 2, 0);
            tempLabel.Content = tempDirInfo.LastAccessTime.ToLongDateString() + ", " + tempDirInfo.LastAccessTime.ToLongTimeString();

            tempRow["Accessed"] = tempLabel;
            tempRow["Location"] = tempDirInfo.FullName;

            data_table.Rows.Add(tempRow);
        }
    }
}

private void PopulateFiles(string[] files)
{
    for (int i = 0; i < files.Length; i++)
    {
        FileInfo tempFileInfo = new FileInfo(files[i]);

        bool isSystem = ((File.GetAttributes(files[i]) & FileAttributes.System) == FileAttributes.System);

        if (!isSystem)
        {
            DataRow tempRow = data_table.NewRow();
            tempRow["File Name"] = tempFileInfo.Name;
            tempRow["Ext"] = tempFileInfo.Extension;

            int fileSize = (int)tempFileInfo.Length;

            if (fileSize > 1048576)
            {
                tempRow["Size"] = "" + fileSize / 1048576 + " MB";
            }
            else if (fileSize > 1024)
            {
                tempRow["Size"] = "" + fileSize / 1024 + " KB";
            }
            else
            {
                tempRow["Size"] = "" + fileSize + " B";
            }

            tempLabel = new Label();
            tempLabel.Padding = new Thickness(2, 0, 2, 0);
            tempLabel.Content = tempFileInfo.CreationTime.ToLongDateString() + ", " + tempFileInfo.CreationTime.ToLongTimeString();

            tempRow["Created"] = tempLabel;

            tempLabel = new Label();
            tempLabel.Padding = new Thickness(2, 0, 2, 0);
            tempLabel.Content = tempFileInfo.LastWriteTime.ToLongDateString() + ", " + tempFileInfo.LastWriteTime.ToLongTimeString();

            tempRow["Modified"] = tempLabel;

            tempLabel = new Label();
            tempLabel.Padding = new Thickness(2, 0, 2, 0);
            tempLabel.Content = tempFileInfo.LastAccessTime.ToLongDateString() + ", " + tempFileInfo.LastAccessTime.ToLongTimeString();

            tempRow["Accessed"] = tempLabel;
            tempRow["Location"] = tempFileInfo.DirectoryName;

            data_table.Rows.Add(tempRow);
        }
    }
}

private string GetSelectedPath(TreeViewItem selectedNode)
{
    return selectedNode.Tag as string;
}

private void PopulateFileList()
{
    PopulateDirectories(Directory.GetDirectories(GetSelectedPath((TreeViewItem)Dir_Tree.SelectedItem)));
    PopulateFiles(Directory.GetFiles(GetSelectedPath((TreeViewItem)Dir_Tree.SelectedItem)));
}

private void UpdateFileList()
{
    LoadingWheel.Visibility = System.Windows.Visibility.Visible;

    CreateFileTable();
    PopulateFileList();
    TxtFoundCount.Text = "Files/Folders Found: " + File_List.Items.Count;

    LoadingWheel.Visibility = System.Windows.Visibility.Hidden;
}

我已经尝试使用BackgroundWorker并在其中调用UpdateFileList（）方法，但我没有运气。

编辑：下面是我的BackgroundWorker代码。

private BackgroundWorker bgWorker1;

private void InitializeBackgroundWorker()
{
    bgWorker1 = new BackgroundWorker();
    bgWorker1.DoWork += new DoWorkEventHandler(bgWorker1_DoWork);
    bgWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bgWorker1_RunWorkerCompleted);
}

private void bgWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    if (Dispatcher.CheckAccess())
    {
        PopulateFileList();
    }
    else
    {
        Dispatcher.Invoke(new Action(() => PopulateFileList()));
    }
}

private void bgWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    TxtFoundCount.Text = "Files/Folders Found: " + File_List.Items.Count;
    LoadingWheel.Visibility = System.Windows.Visibility.Hidden;
}

private void UpdateFileList()
{
    LoadingWheel.Visibility = System.Windows.Visibility.Visible;
    CreateFileTable();
    bgWorker1.RunWorkerAsync();
}

我在TreeView上有一个SelectionChanged事件，它调用InitializeBackgroundWorker（）和UpdateFileList（）。 列表仍然加载，我没有错误，但加载动画永远不会显示。

任何帮助将不胜感激。

谢谢。

Answer 1

只有一个UI线程。 您需要做的是在不同的线程上加载DataTable中的数据。

如果要在整个过程中（直接或通过ProgressBar或其他一些机制）显示DataTable加载的进度， BackgroundWorker是一种相当直接的方法。

更新：非常简单的后台工作者示例
这是一个相当简单的例子。 它为一个集合添加了100个随机数，在每个集合之间暂停一段时间以模拟一个长时间加载过程。 您可以简单地将其剪切并粘贴到您自己的测试项目中以查看它是否有效。

需要注意的是，繁重的工作（需要一段时间的工作）是在DoWork中完成的，而所有UI更新都在ProgressChanged和RunWorkerCompleted中完成。 实际上，在DoWork处理程序中创建了一个单独的列表（数字），因为全局mNumbers集合位于UI线程上，并且无法在DoWork处理程序中进行交互。

XAML

<Button x:Name="btnGenerateNumbers"
        Grid.Row="1"
        HorizontalAlignment="Center"
        VerticalAlignment="Center"
        Content="Generate Numbers" />

C＃Code-Behind

BackgroundWorker bgWorker = new BackgroundWorker();
ObservableCollection<int> mNumbers = new ObservableCollection<int>();

public Window1()
{
    InitializeComponent();
    bgWorker.DoWork += 
        new DoWorkEventHandler(bgWorker_DoWork);
    bgWorker.ProgressChanged += 
        new ProgressChangedEventHandler(bgWorker_ProgressChanged);
    bgWorker.RunWorkerCompleted += 
        new RunWorkerCompletedEventHandler(bgWorker_RunWorkerCompleted);
    bgWorker.WorkerReportsProgress = true;

    btnGenerateNumbers.Click += (s, e) => UpdateNumbers();

    this.DataContext = this;
}

void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    progress.Visibility = Visibility.Collapsed;
    lstItems.Opacity = 1d;
    btnGenerateNumbers.IsEnabled = true;
}

void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    List<int> numbers = (List<int>)e.UserState;
    foreach (int number in numbers)
    {
         mNumbers.Add(number);
    }

    progress.Value = e.ProgressPercentage;
}

void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
    Random rnd = new Random();
    List<int> numbers = new List<int>(10);

    for (int i = 1; i <= 100; i++)
    {
        // Add a random number
        numbers.Add(rnd.Next());            

        // Sleep from 1/8 of a second to 1 second
        Thread.Sleep(rnd.Next(125, 1000));

        // Every 10 iterations, report progress
        if ((i % 10) == 0)
        {
            bgWorker.ReportProgress(i, numbers.ToList<int>());
            numbers.Clear();
        }
    }
}

public ObservableCollection<int> NumberItems
{
    get { return mNumbers; }
}

private void UpdateNumbers()
{
    btnGenerateNumbers.IsEnabled = false;
    mNumbers.Clear();
    progress.Value = 0;
    progress.Visibility = Visibility.Visible;
    lstItems.Opacity = 0.5;

    bgWorker.RunWorkerAsync();
}

Answer 2

我写了一个小测试程序，它显示了Dispatcher类的用法。 它只需要一个WPF-Window和一个名为“listBox”的ListBox。 应该很容易将此解决方案应用于您的问题。

    public void Populate() {
        // for comparison, freezing the ui thread
        for (int i = 0; i < 1000000; i++) {
            listBox.Items.Add(i);
        }
    }

    private delegate void AddItemDelegate(int item);
    public void PopulateAsync() {
        // create a new thread which is iterating the elements
        new System.Threading.Thread(new System.Threading.ThreadStart(delegate() {
            // inside the new thread: iterate the elements
            for (int i = 0; i < 1000000; i++) {
                // use the dispatcher to "queue" the insertion of elements into the UI-Thread
                // DispatcherPriority.Background ensures Animations have a higher Priority and the UI does not freeze
                // possible enhancement: group the "jobs" to small units to enhance the performance
                listBox.Dispatcher.Invoke(new AddItemDelegate(delegate(int item) {
                    listBox.Items.Add(item);
                }), System.Windows.Threading.DispatcherPriority.Background, i);
            }
        })).Start();
    }