如何创建具有键盘焦点的非活动下拉列表

本文关键字：焦点 键盘 非活动 下拉列表 何创建 创建 | 更新日期: 2023-09-27 18:02:20

我想创建一个下拉控件，它应该是不活动的，并有键盘输入焦点。所以我创建了一个控件，如下所示:

public class DropDownEdit : UserControl
{
    [DllImport("user32.dll")]
    public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
    private const int WS_EX_TOOLWINDOW = 0x00000080;
    private const int WS_EX_TOPMOST = 0x00000008;
    private const int WS_EX_NOACTIVATE = 0x08000000;
    private const int WS_CHILD = 0x40000000;
    private const int WS_POPUP = unchecked((int)0x80000000);
    private TextBox text = new TextBox();
    public DropDownEdit()
    {
        this.BackColor = Color.FromArgb(44, 68, 107);
        this.Controls.Add(text);
        this.Margin = Padding.Empty;
        this.Padding = new Padding(0);
        text.Multiline = true;
        text.ScrollBars = ScrollBars.Both;
        text.Size = new Size(this.Width, this.Height);
    }
    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams createParams = base.CreateParams;
            createParams.Style &= ~WS_CHILD;
            createParams.Style |= WS_POPUP;
            createParams.ExStyle |= WS_EX_TOOLWINDOW;
            createParams.ExStyle |= WS_EX_TOPMOST;
            createParams.ExStyle |= WS_EX_NOACTIVATE;
            return createParams;
        }
    }
    public void ShowWindow(Point point)
    {
        text.Focus();
        this.Capture = true;
        SetParent(this.Handle, IntPtr.Zero); 
        this.Location = point;
        Show();
    }
    protected override void OnMouseCaptureChanged(EventArgs e)
    {
        base.OnMouseCaptureChanged(e);
        this.Hide();
    }
}

当我像下面这样显示上面的下拉窗口时，

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    private void button1_Click(object sender, EventArgs e)
    {
        Point point = this.PointToScreen(button1.Location);
        DropDownEdit window = new DropDownEdit();
        window.ShowWindow(new Point(point.X, point.Y + 20));
    }
}

显示DropDownEdit时，Form1闪烁。我认为DropDownEdit被活化，Form1失去活化。如何避免Form1中的闪烁?

NB:-我需要输入焦点在TextBox下拉控件。

如何创建具有键盘焦点的非活动下拉列表

我找到解决办法了。

在显示我的下拉窗口时，它将被激活，而Windows将停用主窗口。解决这个问题的方法是向父程序发送WM_NCACTIVATE消息，在不改变其激活状态的情况下更新其视觉外观。下面的代码是在DropDownEdit类更新，以解决我的问题。

    private const int WM_NCACTIVATE = 0x86;
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    public static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
    protected override void WndProc(ref Message m)
    {
        // The popup needs to be activated for the user to interact with it,
        // but we want to keep the owner window's appearance the same.
        if ((m.Msg == WM_NCACTIVATE) && !_activating && (m.WParam != IntPtr.Zero))
        {
            // The popup is being activated, ensure parent keeps activated appearance
            _activating = true;
            SendMessage(this.Owner.Handle, WM_NCACTIVATE, (IntPtr) 1, IntPtr.Zero);
            _activating = false;
            // Call base.WndProc here if you want the appearance of the popup to change
        }
        else
        {
            base.WndProc(ref m);
        }
    }
相关文章：