鼠标滚轮事件与悬停控件一起使用

Question

在我的 C# 3.5 Windows 窗体应用程序中，我有几个 SplitContainer。每个内部都有一个列表控件（码头填充）。当焦点位于其中一个控件上并且我移动鼠标滚轮时，现在焦点所在的列表会滚动。

我的任务是滚动当前被鼠标悬停的列表，而不是被选中的列表。是否可以在 Windows 窗体中使用？如果没有，是否可以使用 PInvoke？

Answer 1

看起来您可以使用 IMessageFilter 和 PInvoke 来处理此问题。 VB 中的示例可以在Redirect Mouse Wheel Events to Unfocused Windows Forms Controls 找到。您应该能够轻松地将其转换为 C#。

兴趣点

此类对给定任务使用以下技术：

• 监听控件的 MouseEnter 和 MouseLeave 事件以确定鼠标指针何时悬停在控件上。
• 实现 IMessageFilter 以捕获应用程序中的 WM_MOUSEWHEEL 消息。
• PInvoke Windows API 调用 SendMessage 将 WM_MOUSEWHEEL 消息重定向到控件的句柄。
• IMessageFilter 对象实现为 MouseWheelRedirector 类的单例，并由共享成员 Attach、Detach 和 Active 访问。

使用a VB.NET to C# converter，你会得到这样的结果：

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;

using System.Windows.Forms;
using System.Runtime.InteropServices;

public class MouseWheelRedirector : IMessageFilter
{
    private static MouseWheelRedirector instance = null;
    private static bool _active = false;
    public static bool Active
    {
       get { return _active; }
       set
       { 
          if (_active != value) 
          {
             _active = value;
             if (_active)
             {
                if (instance == null)
                {
                    instance = new MouseWheelRedirector();
                }
                Application.AddMessageFilter(instance);
             }
             else
             {
                if (instance != null)
                {
                   Application.RemoveMessageFilter(instance);
                }
             }
          }
       }
    }

    public static void Attach(Control control)
    {
       if (!_active)
          Active = true;
       control.MouseEnter += instance.ControlMouseEnter;
       control.MouseLeave += instance.ControlMouseLeaveOrDisposed;
       control.Disposed += instance.ControlMouseLeaveOrDisposed;
    }

    public static void Detach(Control control)
    {
       if (instance == null)
          return;
       control.MouseEnter -= instance.ControlMouseEnter;
       control.MouseLeave -= instance.ControlMouseLeaveOrDisposed;
       control.Disposed -= instance.ControlMouseLeaveOrDisposed;
       if (object.ReferenceEquals(instance.currentControl, control))
          instance.currentControl = null;
    }

    private MouseWheelRedirector()
    {
    }


    private Control currentControl;
    private void ControlMouseEnter(object sender, System.EventArgs e)
    {
       var control = (Control)sender;
       if (!control.Focused)
       {
          currentControl = control;
       }
       else
       {
          currentControl = null;
       }
    }

    private void ControlMouseLeaveOrDisposed(object sender, System.EventArgs e)
    {
       if (object.ReferenceEquals(currentControl, sender))
       {
          currentControl = null;
       }
    }

    private const int WM_MOUSEWHEEL = 0x20a;
    public bool PreFilterMessage(ref System.Windows.Forms.Message m)
    {
       if (currentControl != null && m.Msg == WM_MOUSEWHEEL)
       {
          SendMessage(currentControl.Handle, m.Msg, m.WParam, m.LParam);
          return true;
       }
       else
       {
          return false;
       }
    }

    [DllImport("user32.dll", SetLastError = false)]
    private static extern IntPtr SendMessage(
       IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
 }

Answer 2

我有类似的问题并找到了这个帖子......所以将我迟来的答案发布给可能找到这个帖子的其他人。就我而言，我只希望鼠标滚轮事件转到光标下的任何控件...就像右键单击一样（如果右键单击转到焦点控件而不是光标下的控件，那将是令人困惑的...我认为鼠标滚轮也是如此，只是我们已经习惯了）。

无论如何，答案非常简单。只需向您的应用程序添加一个 PreFilterMessage 并将鼠标滚轮事件重定向到鼠标下的控件：

    public bool PreFilterMessage(ref Message m)
    {
        switch (m.Msg)
        {
            case WM_MOUSEWHEEL:   // 0x020A
            case WM_MOUSEHWHEEL:  // 0x020E
                IntPtr hControlUnderMouse = WindowFromPoint(new Point((int)m.LParam));
                if (hControlUnderMouse == m.HWnd)
                    return false; // already headed for the right control
                else
                {
                    // redirect the message to the control under the mouse
                    SendMessage(hControlUnderMouse, m.Msg, m.WParam, m.LParam);
                    return true;
                } 
             default: 
                return false; 
           } 
}

Answer 3

这是 Brian Kennedy 的回答，并附有 Hank Schultz 评论：

首先你应该让一个类实现IMessageFilter：

public class MessageFilter : IMessageFilter
{
    private const int WM_MOUSEWHEEL = 0x020A;
    private const int WM_MOUSEHWHEEL = 0x020E;

    [DllImport("user32.dll")]
    static extern IntPtr WindowFromPoint(Point p);
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

    public bool PreFilterMessage(ref Message m)
    {
        switch (m.Msg)
        {
            case WM_MOUSEWHEEL:
            case WM_MOUSEHWHEEL:
                IntPtr hControlUnderMouse = WindowFromPoint(new Point((int)m.LParam));
                if (hControlUnderMouse == m.HWnd)
                {
                    //Do nothing because it's already headed for the right control
                    return false;
                }
                else
                {
                    //Send the scroll message to the control under the mouse
                    uint u = Convert.ToUInt32(m.Msg);   
                    SendMessage(hControlUnderMouse, u, m.WParam, m.LParam);
                    return true;
                }
            default:
                return false;
        }
    }
}

示例用法：

public partial class MyForm : Form
{
    MessageFilter mf = null;

    public MyForm
    {
        Load += MyForm_Load;
        FormClosing += MyForm_FormClosing;
    }

    private void MyForm_Load(object sender, EventArgs e)
    {
        mf= new MessageFilter();
        Application.AddMessageFilter(mf);
    }

    private void MyForm_FormClosing(object sender, FormClosingEventArgs e)
    {
        Application.RemoveMessageFilter(mf);
    }
}

Answer 4

使用Control.MouseEnter Event 将焦点设置到控件。例如。使用ActiveControl Property