c# - listview刷新时焦点不是 "holding"

Question

我目前的代码有一个问题，即无法保持对特定项目行的关注。我创建了 int focusReference 来跟踪当前聚焦的行，但它似乎每隔几秒就会重置为 0，即一旦用户选择了一行，几秒钟后，它“忘记”用户的选择。我在下面包含了一个示例:

正如您从我下面的代码中看到的那样，我有一个计时器每隔几秒执行一次操作。我已经被告知，每隔几秒刷新一次我的列表会导致每隔几秒就会失去焦点。

我如何以编程方式将焦点设置在某个项目上，以保持用户拥有的焦点？我试图实现一个 FocusItem 方法，但它似乎不起作用。这是我程序的一个非常重要的方面，我需要它才能正常工作，否则其他功能(比如我正在实现的右键单击上下文菜单)也将无法工作:

public MainWindow()
{
    InitializeComponent();
    int focusReference = 0;
    PlotListView.SelectionChanged += (s, ee) => { PlotListView_SelectionChanged(s, ee, focusReference); };
    var dbObject = new DbConnect();
    dbObject.OpenConnection();
    RefreshPlotTimer(filterReference, focusReference);
}

public void PlotListView_SelectionChanged(object sender, SelectionChangedEventArgs e, int focusReference)
{
    if (PlotListView.SelectedItems.Count == 0) return;
    var selectedItem = (DbConnect.PlotList)PlotListView.SelectedItems[0];
    focusReference = Convert.ToInt32(selectedItem.PlotId);
    FocusItem(focusReference);
}

private void FocusItem(int focusReference)
{
    if (PlotListView.SelectedItems.Count != 0)
    {
        DbConnect.PlotList plotList =
            PlotListView.Items.OfType<DbConnect.PlotList>()
            .FirstOrDefault(p => Convert.ToInt32(p.PlotId) == focusReference);
        if (plotList != null)
        {
            //get visual container
            var container = PlotListView.ItemContainerGenerator.ContainerFromItem(plotList) as ListViewItem;
            if (container != null)
            {
                container.IsSelected = true;
                container.Focus();
            }
        }
    }
}

public void RefreshPlotTimer(int filterReference, int focusReference)
{
    var refreshTimer = new Timer();
    refreshTimer.Elapsed += (sender, e) => RefreshPlot(sender, e, filterReference, focusReference);
    refreshTimer.Interval = 2500;
    refreshTimer.Enabled = true;
}

public void RefreshPlot(object source, ElapsedEventArgs e, int filterReference, int focusReference)
{
    var dbObject = new DbConnect();
    dbObject.OpenConnection();
    dbObject.RefreshPlot();
    Dispatcher.Invoke(() =>
    {
        FocusItem(focusReference);
        if (!string.IsNullOrWhiteSpace(FilterTextBox.Text) &&
            (!Regex.IsMatch(FilterTextBox.Text, "[^0-9]")))
        {
            filterReference = Convert.ToInt32(FilterTextBox.Text);
        }
    });
    ResetPlot(filterReference);
}

public void ResetPlot(int filterReference)
{
    var dbObject = new DbConnect();
    dbObject.OpenConnection();

    List<DbConnect.PlotList> plotList = dbObject.SelectPlotLists(filterReference);
    Dispatcher.BeginInvoke(
        new ThreadStart(() => PlotListView.ItemsSource = plotList));
    int jobSum = 0;
    int bidSum = 0;
    foreach (DbConnect.PlotList item in PlotListView.Items)
    {
        jobSum += Convert.ToInt32(item.Jobs);
        bidSum += Convert.ToInt32(item.Bids);
    }

    Dispatcher.BeginInvoke(
        new ThreadStart(() => JobBidRatioTextBlock.Text = jobSum + " jobs - " + bidSum + " bids"));
}

更新 2

我又回到了最初使用的代码，会不会是 FocusItem 方法没有保留 listview 项目焦点？

private void FocusItem(int focusReference)
{
    Dispatcher.Invoke(() =>
    {
        if (PlotListView.SelectedItems.Count != 0)
        {
            DbConnect.PlotList plotList =
                PlotListView.Items.OfType<DbConnect.PlotList>()
                    .FirstOrDefault(p => Convert.ToInt32(p.PlotId) == focusReference);
            if (plotList != null)
            {
                //get visual container
                var container = PlotListView.ItemContainerGenerator.ContainerFromItem(plotList) as ListViewItem;
                if (container != null)
                {
                    container.IsSelected = true;
                    container.Focus();
                }
            }
        }
    }
}

我在正确的地方调用它，根据控制台中的内容，索引肯定是正确的。

PlotListView_SelectionChanged 4
Before refresh 4
After refresh 4
PlotListView_SelectionChanged 7
Before refresh 7
After refresh 7

Before refresh 7
After refresh 7

都在刷新绘图方法中...

public void RefreshPlot(object source, ElapsedEventArgs e)
{
    var dbObject = new DbConnect();
    dbObject.OpenConnection();
    dbObject.RefreshPlot();
    Console.WriteLine("\rBefore refresh " + focusReference);
    Dispatcher.Invoke(() =>
    {
        if (!string.IsNullOrWhiteSpace(FilterTextBox.Text) &&
            (!Regex.IsMatch(FilterTextBox.Text, "[^0-9]")))
        {
            filterReference = Convert.ToInt32(FilterTextBox.Text);
        }
    });
    ResetPlot(filterReference);
    Console.WriteLine("After refresh " + focusReference);
    FocusItem(focusReference);
}

以及重置绘图方法...

public void ResetPlot(int filterReference)
{
    // Establish MySQL connection
    var dbObject = new DbConnect();
    dbObject.OpenConnection();

    // Fill plot list view
    List<DbConnect.PlotList> plotList = dbObject.SelectPlotLists(filterReference);
    Dispatcher.BeginInvoke(
        new ThreadStart(() => PlotListView.ItemsSource = plotList));
    int jobSum = 0;
    int bidSum = 0;
    foreach (DbConnect.PlotList item in PlotListView.Items)
    {
        jobSum += Convert.ToInt32(item.Jobs);
        bidSum += Convert.ToInt32(item.Bids);
    }
    FocusItem(focusReference);

    // Determine job/bid list ratio
    Dispatcher.BeginInvoke(
        new ThreadStart(() => JobBidRatioTextBlock.Text = jobSum + " jobs - " + bidSum + " bids"));
}

Answer 1

在进行刷新之前，您需要记住 SelectedItem 并在刷新后重新设置它。这就是理论。

在对象的情况下，你需要找到哪个现在与之前的相同(因为它不再是同一个实例)所以你必须在新的结果列表中搜索它并将它分配给SelectedItem。

最简单的方法是重新设置 SelectedIndex，但由于列表可能发生变化，它迟早会重新选择错误的项目。

// Gets current selection.
public DbConnect.PlotList SelectedPlotList
{
    get
    {
        return PlotListView.SelectedItem as DbConnect.PlotList;
    }
}
public void ResetPlot(int filterReference)
{
    // Get current plot number;
    int? plotNumber = SelectedPlotList == null ? (int?)null : SelectedPlotList.PlotNumber;

    var dbObject = new DbConnect();
    dbObject.OpenConnection();

    List<DbConnect.PlotList> plotList = dbObject.SelectPlotLists(filterReference);

    // Find the plot list in the new list.  
    DbConnect.PlotList selectPlotList = 
        plotNumber.HasValue
        ? plotList.Where(x => x.PlotNumber == plotNumber.Value).FirstOrDefault();
        : null;
    Dispatcher.BeginInvoke(new ThreadStart(() => PlotListView.ItemsSource = plotList));

    // Re-select plot list if found in the new list.
    if (selectPlotList != null)
    {
        PlotListView.SelectedItem = selectPlotList;
    }
    int jobSum = 0;
    int bidSum = 0;


    foreach (DbConnect.PlotList item in PlotListView.Items)
    {
        jobSum += Convert.ToInt32(item.Jobs);
        bidSum += Convert.ToInt32(item.Bids);
    }

    Dispatcher.BeginInvoke(
        new ThreadStart(() => JobBidRatioTextBlock.Text = jobSum + " jobs - " + bidSum + " bids"));
}

编辑:

我刚刚测试了一个快速且粗略的演示，它可以正常工作。其他地方一定有错误。

这会生成 7 个具有唯一 ID 的项目，如果再次绘制则重新选择最后选择的项目:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        List<ListViewItem> items = new List<ListViewItem>();
        Random rnd = new Random(DateTime.Now.Millisecond);
        HashSet<int> ids = new HashSet<int>();
        for (int i = 0; i < 7; i++)
        {
            int id = 0;
            do
            {
                id = rnd.Next(0, 10);
            } while (ids.Contains(id));
            ids.Add(id);
            items.Add(new ListViewItem() { Id = id, Name = "Item-" + i });
        }
        int? selectedId = listView1.SelectedItem != null ? (listView1.SelectedItem as ListViewItem).Id : (int?)null;
        listView1.ItemsSource = items;

        if (selectedId.HasValue)
        {
            listView1.SelectedItem = items.Where(x => x.Id == selectedId).FirstOrDefault();
            listView1.Focus();
        }
    }
}

class ListViewItem
{
    public int Id { get; set; }
    public string Name { get; set; }
}