prevent listview to lose selected item

问题

I'm currently working on a listview in winform c# and everytime I click on an empty space on the listview, the selected item is lost.

回答1:

The listview control has a HideSelection property that defaults to True. Make it False and you're good to go... in some cases this is enough.

回答2:

I thought there was a property that prevented this from happening, but now I can't find it.

You could try this:

private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    ListView listView = sender as ListView;
    if (listView.SelectedItems.Count == 0)
        foreach (object item in e.RemovedItems)
            listView.SelectedItems.Add(item);
}

回答3:

I accomplished it like this:

private void lvReads_MouseUp(object sender, MouseEventArgs e)
    {
        if (lvReads.SelectedItems.Count == 0)
            if (lvReads.Items.Count > 0)
                lvReads.Items.Find(currentName, false)[0].Selected = true;
    }

and

private void lvReads_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (lvReads.SelectedItems.Count == 1)
        {               
            selectedIndex = lvReads.SelectedIndices[0];

            if (currentName != lvReads.Items[selectedIndex].Name)
            {

                //load item
            }

            currentName = lvReads.Items[selectedIndex].Name;
        }
    }

回答4:

You have to inherit from the ListView class and do some low-level message processing

class ListViewThatKeepsSelection : ListView
{
    protected override void WndProc(ref Message m)
    {
        // Suppress mouse messages that are OUTSIDE of the items area
        if (m.Msg >= 0x201 && m.Msg <= 0x209)
        {
            Point pos = new Point(m.LParam.ToInt32() & 0xffff, m.LParam.ToInt32() >> 16);
            var hit = this.HitTest(pos);
            switch (hit.Location)
            {
                case ListViewHitTestLocations.AboveClientArea:
                case ListViewHitTestLocations.BelowClientArea:
                case ListViewHitTestLocations.LeftOfClientArea:
                case ListViewHitTestLocations.RightOfClientArea:
                case ListViewHitTestLocations.None:
                    return;
            }
        }
        base.WndProc(ref m);
    }
}

回答5:

This is much harder to do in WinForms than in WPF. WinForms has a SelectedIndexChanged event which doesn't tell you anything about what was already selected, plus it is fired every time a row is selected or deselected.

So if a row is selected and you select a different row, you receive two SelectedIndexChanged events:

one after the selected row is deselected
another when the new row is selected.

The problem is that, during event #1, the ListView has nothing selected and you don't know if event #2 is coming that will select the second row.

The best you can do is wait until your application is idle (a few milliseconds after the selection has changed), and if the listview still has nothing selected, put back the last selected row.

private void listView1_SelectedIndexChanged(object sender, EventArgs e)
{
    ListView lv = (ListView)sender;
    if (lv.SelectedIndices.Count == 0)
    {
        if (!this.appIdleEventScheduled)
        {
            this.appIdleEventScheduled = true;
            this.listViewToMunge = lv;
            Application.Idle += new EventHandler(Application_Idle);
        }
    }
    else
        this.lastSelectedIndex = lv.SelectedIndices[0];
}

void Application_Idle(object sender, EventArgs e)
{
    Application.Idle -= new EventHandler(Application_Idle);
    this.appIdleEventScheduled = false;
    if (listViewToMunge.SelectedIndices.Count == 0) 
        listViewToMunge.SelectedIndices.Add(this.lastSelectedIndex);
}

private bool appIdleEventScheduled = false;
private int lastSelectedIndex = -1;
private ListView listViewToMunge;

来源：https://stackoverflow.com/questions/2382369/prevent-listview-to-lose-selected-item

标签

winforms

listview

selection