c# - 如何在不窃取焦点且不使用 P/Invoke 的情况下将消息(例如鼠标滚轮)转发到另一个控件？

Question

我想在我用鼠标悬停在这个控件上时转发一条消息(例如 WM_MOUSEWHEEL)，而不窃取焦点。使用 IMessageFilter(将添加到应用程序消息泵)拦截消息并使用 P/Invoke(d) SendMessage() 转发它可以轻松解决此问题。问题是:我可以在不使用 P/Invoke 的情况下做同样的事情吗(我在 StackOverflow 中找到的解决方案使用 P/Invoke)？如果不是，为什么？

下面的代码是我使用 P/Invoke 的解决方案。我只将它与 new MessageForwarder(control, 0x20A) 一起使用。

/// <summary>
/// This class implements a filter for the Windows.Forms message pump allowing a
/// specific message to be forwarded to the Control specified in the constructor.
/// Adding and removing of the filter is done automatically.
/// </summary>
public class MessageForwarder : IMessageFilter
{
#region Fields

private Control _Control;
private Control _PreviousParent;
private HashSet<int> _Messages;
private bool _IsMouseOverControl;

#endregion // Fields

#region Constructors

public MessageForwarder(Control control, int message)
    : this(control, new int[] { message }) { }

public MessageForwarder(Control control, IEnumerable<int> messages)
{
    _Control = control;
    _Messages = new HashSet<int>(messages);
    _PreviousParent = control.Parent;
    _IsMouseOverControl = false;

    control.ParentChanged += new EventHandler(control_ParentChanged);
    control.MouseEnter += new EventHandler(control_MouseEnter);
    control.MouseLeave += new EventHandler(control_MouseLeave);
    control.Leave += new EventHandler(control_Leave);

    if (control.Parent != null)
        Application.AddMessageFilter(this);
}

#endregion // Constructors

#region IMessageFilter members

public bool PreFilterMessage(ref Message m)
{
    if (_Messages.Contains(m.Msg) && _Control.CanFocus && !_Control.Focused
        && _IsMouseOverControl)
    {
        SendMessage(_Control.Handle, m.Msg, m.WParam, m.LParam);
        return true;
    }

    return false;
}

#endregion // IMessageFilter

#region Event handlers

void control_ParentChanged(object sender, EventArgs e)
{
    if (_Control.Parent == null)
        Application.RemoveMessageFilter(this);
    else
    {
        if (_PreviousParent == null)
            Application.AddMessageFilter(this);
    }
    _PreviousParent = _Control.Parent;
}

void control_MouseEnter(object sender, EventArgs e)
{
    _IsMouseOverControl = true;
}

void control_MouseLeave(object sender, EventArgs e)
{
    _IsMouseOverControl = false;
}

void control_Leave(object sender, EventArgs e)
{
    _IsMouseOverControl = false;
}

#endregion // Event handlers

#region Support

[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);

#endregion // Support

编辑:我回答中的完整解决方案

Answer 1

找到一个方法:你必须继承NativeWindow，将所选控件的句柄分配给它，并在你以任何你喜欢的方式拦截消息后调用 protected WndProc(在我的例子中，继承的类甚至是一个 IMessageFilter，所以我可以轻松地将它插入应用程序)。我将它与 new MessageForwarder(anycontrol, 0x20A) 一起使用以重定向鼠标滚轮。

因此可以在没有 p/invoke 的情况下拦截消息并将其转发给任何控件。虽然它隐藏得很好。

/// <summary>
/// This class implements a filter for the Windows.Forms message pump allowing a
/// specific message to be forwarded to the Control specified in the constructor.
/// Adding and removing of the filter is done automatically.
/// </summary>
public class MessageForwarder : NativeWindow, IMessageFilter
{
    #region Fields

    private Control _Control;
    private Control _PreviousParent;
    private HashSet<int> _Messages;
    private bool _IsMouseOverControl;

    #endregion // Fields

    #region Constructors

    public MessageForwarder(Control control, int message)
        : this(control, new int[] { message }) { }

    public MessageForwarder(Control control, IEnumerable<int> messages)
    {
        _Control = control;
        AssignHandle(control.Handle);
        _Messages = new HashSet<int>(messages);
        _PreviousParent = control.Parent;
        _IsMouseOverControl = false;

        control.ParentChanged += new EventHandler(control_ParentChanged);
        control.MouseEnter += new EventHandler(control_MouseEnter);
        control.MouseLeave += new EventHandler(control_MouseLeave);
        control.Leave += new EventHandler(control_Leave);

        if (control.Parent != null)
            Application.AddMessageFilter(this);
    }

    #endregion // Constructors

    #region IMessageFilter members

    public bool PreFilterMessage(ref Message m)
    {
        if (_Messages.Contains(m.Msg) && _Control.CanFocus && !_Control.Focused
            && _IsMouseOverControl)
        {
            m.HWnd = _Control.Handle;
            WndProc(ref m);
            return true;
        }

        return false;
    }

    #endregion // IMessageFilter

    #region Event handlers

    void control_ParentChanged(object sender, EventArgs e)
    {
        if (_Control.Parent == null)
            Application.RemoveMessageFilter(this);
        else
        {
            if (_PreviousParent == null)
                Application.AddMessageFilter(this);
        }
        _PreviousParent = _Control.Parent;
    }

    void control_MouseEnter(object sender, EventArgs e)
    {
        _IsMouseOverControl = true;
    }

    void control_MouseLeave(object sender, EventArgs e)
    {
        _IsMouseOverControl = false;
    }

    void control_Leave(object sender, EventArgs e)
    {
        _IsMouseOverControl = false;
    }

    #endregion // Event handlers
}