关闭时如何从键箭头 Up\Down 禁用组合框的滚动？

Question

箭头键应该只滚动图片框（放置在面板中）。它工作正常。但它也会滚动浏览 comboBox 项目，尽管它是关闭的 (droppedUp)。如何禁用它？

private void Form1_Load(object sender, EventArgs e)
{
     comboBox1.DropDownStyle = ComboBoxStyle.DropDown;
     comboBox1.DroppedDown = false;
     comboBox1.Items.Add("111");
     comboBox1.Items.Add("222");
}
 
protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
    if (keyData == Keys.Down)
    {
          Point current = panel1.AutoScrollPosition;
          Point scrolled = new Point(current.X, -current.Y + 50);
          panel1.AutoScrollPosition = scrolled;
    }

    return base.ProcessCmdKey(ref msg, keyData);
}

我读过 Control.PreviewKeyDown 事件： preview key event 还找到了另一个例子： preview key event 但我无法理解它在我的案例中是如何使用的。

Answer 1

正如 Hans Passant 评论的那样，您必须 return 正确。此外，添加一些其他键可能会更改组合框中的选定项目：

protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
    if (keyData == Keys.Down || 
        keyData == Keys.Up ||
        keyData == Keys.PageDown ||
        keyData == Keys.PageUp)
    {
        Point current = panel1.AutoScrollPosition;
        Point scrolled = new Point(current.X, -current.Y + 50);
        panel1.AutoScrollPosition = scrolled;
        return true;
    }

    return base.ProcessCmdKey(ref msg, keyData);
}

关闭时如何从键箭头 Up\Down 禁用组合框的滚动？

How to disable scrolling of comboBox from keys arrow Up\Down when it closed?

c#

winforms