用户控件：如何添加鼠标滚轮侦听器？

问题描述

我创建一个用户控件应该作出反应，如果鼠标在控制和鼠标滚轮旋转得到

I'm creating an UserControl that should react if the mouse is over the control and MouseWheel gets rotated.

目前我这样做如下所示：

Currently i'm doing this as shown here:

    public MyUserControl()
    {
        this.MouseWheel += new MouseEventHandler(MouseWheelHandler);
    }

    private void MouseWheelHandler(object sender, System.Windows.Forms.MouseEventArgs e)
    {
        if (e.Delta > 0)
            incIndex();

        if (e.Delta < 0)
            decIndex();
    }

    protected override void OnMouseEnter(EventArgs e)
    {
        this.Focus();

        base.OnMouseEnter(e);
    }

在实际上这工作得很好，但问题是用这部分。焦点（）;因为它破坏我的表格/应用程序的行为。

In fact this works fine, but the problem is the part with the "this.Focus();" as it destroys my forms / applications behaviour.

有没有更好的办法才达到这一点？

Is there a better way to achive this?

推荐答案

有同样的问题，我终于落实，通过解决方案和@Paul_Westcott NR1 @的混合。这就像@Paul_Westcott的溶液局部解（仅适用于预订该WinForms的控制）。这是（在应用程序中被其他窗口重叠的）多个监控安全和MDI安全

having the same problem, I finally implemented a mix of both solution by @Paul_Westcott and @nr1. This is a local solution like solution of @Paul_Westcott (only applies to the winforms control that subscribes to). It is multiple monitor safe and MDI safe (overlapping by other windows within the application)

public static class MouseWheelHandlerForWinformsControl
{
    private class MouseWheelMessageFilter : IMessageFilter
    {
        [DllImport("user32.dll")]
        private static extern IntPtr WindowFromPoint(Point pt);

        private readonly Control mCtrl;
        private readonly Action<MouseEventArgs> mOnMouseWheel;

        public MouseWheelMessageFilter(Control ctrl, Action<MouseEventArgs> onMouseWheel)
        {
            mCtrl = ctrl;
            mOnMouseWheel = onMouseWheel;
        }

        public bool PreFilterMessage(ref Message m)
        {
            // handle only mouse wheel messages
            if (m.Msg != 0x20a)
                return false;

            Point mouseAbsolutePosition = new Point(m.LParam.ToInt32());
            Point mouseRelativePosition = mCtrl.PointToClient(mouseAbsolutePosition);

            IntPtr hControlUnderMouse = WindowFromPoint(mouseAbsolutePosition);
            Control controlUnderMouse = Control.FromHandle(hControlUnderMouse);

            if (controlUnderMouse != mCtrl)
                return false;

            MouseButtons buttons = GetMouseButtons(m.WParam.ToInt32());
            int delta = m.WParam.ToInt32() >> 16;

            var e = new MouseEventArgs(buttons, 0, mouseRelativePosition.X, mouseRelativePosition.Y, delta);

            mOnMouseWheel(e);

            return true;
        }

        private static MouseButtons GetMouseButtons(int wParam)
        {
            MouseButtons buttons = MouseButtons.None;

            if(HasFlag(wParam, 0x0001)) buttons |= MouseButtons.Left;
            if(HasFlag(wParam, 0x0010)) buttons |= MouseButtons.Middle;
            if(HasFlag(wParam, 0x0002)) buttons |= MouseButtons.Right;
            if(HasFlag(wParam, 0x0020)) buttons |= MouseButtons.XButton1;
            if(HasFlag(wParam, 0x0040)) buttons |= MouseButtons.XButton2;

            return buttons;
        }

        private static bool HasFlag(int input, int flag)
        {
            return (input & flag) == flag;
        }
    }

    public static void MemorySafeAdd(Control ctrl, Action<MouseEventArgs> onMouseWheel)
    {
        if (ctrl == null || onMouseWheel == null)
            throw new ArgumentNullException();

        var filter = new MouseWheelMessageFilter(ctrl, onMouseWheel);
        Application.AddMessageFilter(filter);
        ctrl.Disposed += (s, e) => Application.RemoveMessageFilter(filter);
    }
}

一旦你加入这个辅助类到您的解决方案，您订阅控制 myControl 将鼠标滚轮，在一个行，如下：

Once you have added this helper class into your solution, you subscribe a control myControl to the mouse-wheel, in one line, as following:

public void Init() {
    MouseWheelHandlerForWinformsControl.MemorySafeAdd(myControl, OnMouseWheelEvent);
}

void OnMouseWheelEvent(MouseEventArgs args) {
    // do what you need here
}

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