Question

在一个事件中，我想把重点放在ListViewItem模板中的特定TextBox上。 XAML看起来像这样：

<ListView x:Name="myList" ItemsSource="{Binding SomeList}">
    <ListView.View>
        <GridView>
            <GridViewColumn>
                <GridViewColumn.CellTemplate>
                    <DataTemplate>
                        <!-- Focus this! -->
                        <TextBox x:Name="myBox"/>

我在后面的代码中尝试了以下内容：

(myList.FindName("myBox") as TextBox).Focus();

但我似乎误解了FindName()个文档，因为它返回null。

ListView.Items也无济于事，因为（当然）包含我绑定的业务对象而没有ListViewItems。

myList.ItemContainerGenerator.ContainerFromItem(item)也没有，它也返回null。

Answer 1

要理解为什么ContainerFromItem对我不起作用，这里有一些背景知识。我需要此功能的事件处理程序如下所示：

var item = new SomeListItem();
SomeList.Add(item);
ListViewItem = SomeList.ItemContainerGenerator.ContainerFromItem(item); // returns null

Add()后ItemContainerGenerator没有立即创建容器，因为可以在非UI线程上处理CollectionChanged事件。相反，它启动异步调用并等待UI线程回调并执行实际的ListViewItem控件生成。

要在发生这种情况时收到通知，ItemContainerGenerator会公开在生成所有容器后触发的StatusChanged事件。

现在我必须听这个事件并决定控件当前是否想要设置焦点。

Answer 2

正如其他人所说，通过在ListView上调用FindName无法找到myBox TextBox。但是，您可以获取当前选定的ListViewItem，并使用VisualTreeHelper类从ListViewItem获取TextBox。这样做看起来像这样：

private void myList_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (myList.SelectedItem != null)
    {
        object o = myList.SelectedItem;
        ListViewItem lvi = (ListViewItem)myList.ItemContainerGenerator.ContainerFromItem(o);
        TextBox tb = FindByName("myBox", lvi) as TextBox;

        if (tb != null)
            tb.Dispatcher.BeginInvoke(new Func<bool>(tb.Focus));
    }
}

private FrameworkElement FindByName(string name, FrameworkElement root)
{
    Stack<FrameworkElement> tree = new Stack<FrameworkElement>();
    tree.Push(root);

    while (tree.Count > 0)
    {
        FrameworkElement current = tree.Pop();
        if (current.Name == name)
            return current;

        int count = VisualTreeHelper.GetChildrenCount(current);
        for (int i = 0; i < count; ++i)
        {
            DependencyObject child = VisualTreeHelper.GetChild(current, i);
            if (child is FrameworkElement)
                tree.Push((FrameworkElement)child);
        }
    }

    return null;
}

Answer 3

我注意到问题标题与问题的内容没有直接关系，接受的答案也没有回答。我已经能够“使用这个来访问WPF ListView的ListViewItems”：

public static IEnumerable<ListViewItem> GetListViewItemsFromList(ListView lv)
{
    return FindChildrenOfType<ListViewItem>(lv);
}

public static IEnumerable<T> FindChildrenOfType<T>(this DependencyObject ob)
    where T : class
{
    foreach (var child in GetChildren(ob))
    {
        T castedChild = child as T;
        if (castedChild != null)
        {
            yield return castedChild;
        }
        else
        {
            foreach (var internalChild in FindChildrenOfType<T>(child))
            {
                yield return internalChild;
            }
        }
    }
}

public static IEnumerable<DependencyObject> GetChildren(this DependencyObject ob)
{
    int childCount = VisualTreeHelper.GetChildrenCount(ob);

    for (int i = 0; i < childCount; i++)
    {
        yield return VisualTreeHelper.GetChild(ob, i);
    }
}

我不确定递归会有多忙，但在我的情况下似乎工作正常。不，我之前没有在递归上下文中使用yield return。

Answer 4

您可以遍历ViewTree以查找项目＆＃39; ListViewItem ＆＃39;与命中测试触发的单元格对应的记录集。

同样，您可以从父视图中获取列标题，以比较和匹配单元格的列。您可能希望将单元名称绑定到列标题名称，作为比较器委托/过滤器的键。

例如：HitResult在TextBlock上以绿色显示。您希望获得＆＃39; ListViewItem 的句柄。

/// <summary>
///   ListView1_MouseMove
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void ListView1_MouseMove(object sender, System.Windows.Input.MouseEventArgs e) {
  if (ListView1.Items.Count <= 0)
    return;

  // Retrieve the coordinate of the mouse position.
  var pt = e.GetPosition((UIElement) sender);

  // Callback to return the result of the hit test.
  HitTestResultCallback myHitTestResult = result => {
    var obj = result.VisualHit;

    // Add additional DependancyObject types to ignore triggered by the cell's parent object container contexts here.
    //-----------
    if (obj is Border)
      return HitTestResultBehavior.Stop;
    //-----------

    var parent = VisualTreeHelper.GetParent(obj) as GridViewRowPresenter;
    if (parent == null)
      return HitTestResultBehavior.Stop;

    var headers = parent.Columns.ToDictionary(column => column.Header.ToString());

    // Traverse up the VisualTree and find the record set.
    DependencyObject d = parent;
    do {
      d = VisualTreeHelper.GetParent(d);
    } while (d != null && !(d is ListViewItem));

    // Reached the end of element set as root's scope.
    if (d == null)
      return HitTestResultBehavior.Stop;

    var item = d as ListViewItem;
    var index = ListView1.ItemContainerGenerator.IndexFromContainer(item);
    Debug.WriteLine(index);

    lblCursorPosition.Text = $"Over {item.Name} at ({index})";

    // Set the behavior to return visuals at all z-order levels.
    return HitTestResultBehavior.Continue;
  };

  // Set up a callback to receive the hit test result enumeration.
  VisualTreeHelper.HitTest((Visual)sender, null, myHitTestResult, new PointHitTestParameters(pt));
}

Answer 5

我们在WPF的新数据网格中使用了类似的技术：

Private Sub SelectAllText(ByVal cell As DataGridCell)
    If cell IsNot Nothing Then
        Dim txtBox As TextBox= GetVisualChild(Of TextBox)(cell)
        If txtBox IsNot Nothing Then
            txtBox.Focus()
            txtBox.SelectAll()
        End If
    End If
End Sub

Public Shared Function GetVisualChild(Of T As {Visual, New})(ByVal parent As Visual) As T
    Dim child As T = Nothing
    Dim numVisuals As Integer = VisualTreeHelper.GetChildrenCount(parent)
    For i As Integer = 0 To numVisuals - 1
        Dim v As Visual = TryCast(VisualTreeHelper.GetChild(parent, i), Visual)
        If v IsNot Nothing Then
            child = TryCast(v, T)
            If child Is Nothing Then
                child = GetVisualChild(Of T)(v)
            Else
                Exit For
            End If
        End If
    Next
    Return child
End Function

该技术应该适用于您，只需在生成后传递listviewitem即可。

Answer 6

或者可以通过

完成

private void yourtextboxinWPFGrid_LostFocus(object sender, RoutedEventArgs e)
    {
       //textbox can be catched like this. 
       var textBox = ((TextBox)sender);
       EmailValidation(textBox.Text);
    }

如何访问WPF ListView的ListViewItem？

6 个答案: