如何使用keybord焦点创建非活动下拉列表

问题描述

我想创建一个下拉控件，该控件应该处于非活动状态并具有键盘输入焦点。所以我创建了一个控件如下。

I want to create a dropdown control which should be inactive and have keyboard input focus. So I created a control as below.

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();
    }
}

当我显示上面的下拉窗口时，

And when I am displaying the above dropdown window as below,

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));
    }
}

Form1 有一个显示 DropDownEdit 时闪烁。我认为 DropDownEdit 被激活， Form1 失去激活。如何在 Form1 中避免这种闪烁？

注意： - 我需要输入焦点 TextBox 在下拉控件中。

The Form1 has a flickering while displaying DropDownEdit. I think DropDownEdit get activated and Form1 loses its activation. How can I avoid this flickering in Form1?
NB:- I need input focus on TextBox in the dropdown control.

推荐答案

myControl.Parent = someOtherControl;

或使用

or using

someOtherControl.Controls.Add(myControl);

P / Invoke不是绝对必需的，它使用起来很糟糕;它会破坏你代码的平台兼容性。

-SA

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);
    }
}

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