用户控件：如何添加鼠标滚轮侦听器？ [英] UserControl: How to add MouseWheel Listener?

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
}

这篇关于用户控件：如何添加鼠标滚轮侦听器？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！