删除项目后以编程方式更改列表框中的 SelectedIndex

Question

I would like to remove items from a ListBox and set the selected index to the next item.

<ListBox x:Name="lstBox" KeyDown="lstBox_KeyDown">
            <ListBoxItem>A</ListBoxItem>
            <ListBoxItem>B</ListBoxItem>
            <ListBoxItem>C</ListBoxItem>
            <ListBoxItem>D</ListBoxItem>
            <ListBoxItem>E</ListBoxItem>
</ListBox>

This code works as intended unless i use the arrow keys. If i delete "B" for instance the next selected item is "C". However using cursor down will select the first item "A" instead of "D".

 private void lstBox_KeyDown(object sender, KeyEventArgs e)
        {

            if (e.Key == Key.Delete)
            {

                if (lstBox.SelectedIndex == -1)
                    return;

                int currentIndex = lstBox.SelectedIndex;
                int newIndex = lstBox.SelectedIndex;

                //in case the last item was deleted
                if (newIndex == lstBox.Items.Count - 1)
                    newIndex--;

                lstBox.Items.RemoveAt(currentIndex);

                lstBox.SelectedIndex = newIndex;
            }
        }

I have already tried to set the focus to the ListBox after setting the new index. But it doesn't help.

lstBox.SelectedIndex = newIndex;
lstBox.Focus();

How can i fix that?

Answer 1

This issue is due to the fact that when you are removing one item, ListBox loses the focus. So in order to make your arrow keys work, you will also have to set the focus on Selected Item of the Listbox

<ListBox x:Name="lstBox" KeyDown="lstBox_KeyDown" SelectionChanged="LstBox_OnSelectionChanged">
            <ListBoxItem>A</ListBoxItem>
            <ListBoxItem>B</ListBoxItem>
            <ListBoxItem>C</ListBoxItem>
            <ListBoxItem>D</ListBoxItem>
            <ListBoxItem>E</ListBoxItem>
</ListBox>

---

private void LstBox_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
    var item = (ListBoxItem)lstBox.ItemContainerGenerator.ContainerFromItem(lstBox.SelectedItem);

    if (item != null)
         item.Focus();
}