.net - 如何获取多选列表框中的最后一个选定项？

Question

如何获取 .Net Forms 多选列表框中的最后一个选定项目？显然，如果我在列表框中选择一个项目，然后再选择 10 个，则所选项目是第一个。

我想获得我选择/取消选择的最后一个元素。

Answer 1

我会采用这种一般方法：

每次监听SelectedIndexChanged事件并扫描集合。SelectedIndices

保留所有选定索引的单独列表，附加未在列表中的索引，删除已取消选择的索引。

单独的列表将按用户选择的时间顺序包含索引。最后一个元素始终是最近选择的索引。

// for the sake of the example, I defined a single List<int>
List<int> listBox1_selection = new List<int>();

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    TrackSelectionChange((ListBox)sender, listBox1_selection);
}

private void TrackSelectionChange(ListBox lb, List<int> selection)
{
    ListBox.SelectedIndexCollection sic = lb.SelectedIndices;
    foreach (int index in sic)
        if (!selection.Contains(index)) selection.Add(index);

    foreach (int index in new List<int>(selection))
        if (!sic.Contains(index)) selection.Remove(index);
}

Answer 2

不确定我是否理解这个问题，但最后一个选定的项目将是 SelectedItems 数组中的最后一个，所以这样的事情应该可以工作：

ListItem i = list.SelectedItems[list.SelectedItems.Length-1];

Answer 3

在列表框的鼠标单击事件中使用以下代码：

private void ListBox1_MouseClick(object sender, MouseEventArgs e)
{
    string s = ListBox1.Items[ListBox1.IndexFromPoint(e.Location)].ToString();

    MessageBox.Show(s);
}

Answer 4

试试这个

 private void listBox1_MouseUp(object sender, MouseEventArgs e)
    {
        int jj = listBox1.IndexFromPoint(e.X, e.Y);
        object Test = listBox1.Items[jj];
        object LatestItemSelected;
        if(listBox1.SelectedItems.Contains(Test))
            LatestItemSelected = Test;
    }

显然， LatestItemSelected是多余的，是为了强调您已经找到了您的项目。

Answer 5

使用一些反射来获取 FocusedIndex 的值，这是 ListBox 的内部属性，您可以获得最后一个关注的项目。

int lastSelectedIndex = (int)typeof(ListBox).GetProperty("FocusedIndex",BindingFlags.NonPublic|BindingFlags.Instance).GetValue(myListBox,null);
SelectedItemType mySelectedItem = myListBox.Items[lastSelectedIndex] as SelectedItemType;

Answer 6

使用 FocusManager.GetFocusedElement(listbox) 或 Keyboard.FocusedElement 返回您选择的最后一项。

Answer 7

我在 VBA 中遇到了完全相同的问题...想法是在隐藏标签中记录以前的选择...然后将列表框中的所有选定项目与记录的以前的选择进行比较...如果它不存在在标签中，这是最后一个选定的项目。我已经对其进行了测试，并且可以正常工作……您将不得不稍微调整一下代码，但这个想法对我有用。

Private Sub ListBox2_Change()
    
    'Preview Doc
    Previous_Selections = Me.Label2.Caption
    
    'This logic figures out the last selected item if you already have existing selections
    For i = 0 To ListBox2.ListCount - 1
         If ListBox2.Selected(i) Then
            MyItem = ListBox2.List(i)
            
            'Check if this is a new selection or and old one
            If IsIn(MyItem, Previous_Selections) = False Then
            
                'This is a new selection
                'Record new selection for as 'previous' for next time
                For n = 0 To ListBox2.ListCount - 1
                    If ListBox2.Selected(n) Then Selections = Selections & ListBox2.List(n) & ", "
                Next
                
                'Preview last selected item
                FullPath = Me.ListBox1.Value & "\" & MyItem
                Me.Label2.Caption = Selections
                Call Preview_Document(FullPath)
                Exit Sub
            End If
         End If
    Next i
    
    
   
End Sub

Answer 8

这是我在VB中完成的方式。

当您刷新列表框时，您必须重新调整数组的尺寸。

  Dim SelectedAry(-1) As Integer

  Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox1.SelectedIndexChanged
        Dim LastOne As Integer = -1
        ' First time there no elements in the preserved array
        If SelectedAry.Length = 0 Then
              If ListBox1.SelectedIndex <> -1 Then
                    LastOne = 0
              End If
        Else
              'If the SelectedIndices array is larger than the preserved SelectedAry - means that another one had been selected
              If ListBox1.SelectedIndices.Count >= SelectedAry.Length Then
                    For i = 0 To ListBox1.SelectedIndices.Count - 1
                          'Go through both arrays comparing the values until there is a mismatch
                          'This means that the value in the  SelectesIndices is the last one to be added
                          If ListBox1.SelectedIndices(i) <> SelectedAry(i) Then
                                LastOne = i
                                Exit For
                          End If
                    Next
              End If
        End If
        ' Copy the Listbox selectedindices array into the SelectedAry which is preserved for the next selected index change
        ReDim SelectedAry(ListBox1.SelectedIndices.Count)
        For i = 0 To ListBox1.SelectedIndices.Count - 1
              SelectedAry(i) = ListBox1.SelectedIndices(i)
        Next
        ' Display the last one added
        If LastOne >= 0 Then
              Dim FileName As String = txtFolder.Text & "\" & ListBox1.Items(ListBox1.SelectedIndices(LastOne)).ToString
              Display_File(FileName)
        Else
        End If
  End Sub