[.NET]讓Panel對Mouse滾輪事件(Wheel)有感覺，而且能觸發Scroll事件

2013-12-03

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.NET

之前有寫了一篇「讓Panel對Mouse滾輪事件(Wheel)有感覺」，是透過 SendMessage 的方式去叫 Panel Scroll。
但是卻不會觸發Panel的Scroll事件。那怎麼辦呢?

在之前有寫了一篇「讓Panel對Mouse滾輪事件(Wheel)有感覺」，是透過 SendMessage 的方式去叫 Panel Scroll。

但是卻不會觸發Panel的Scroll事件。那怎麼辦呢?

所以我們可以透過Control.FromHandle來取到那個控制項，然後再觸發該控制項的Scroll事件，如下，


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form, IMessageFilter
    {

        // P/Invoke declarations
        [DllImport("user32.dll")]
        private static extern IntPtr WindowFromPoint(Point pt);

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

        public Form1()
        {
            InitializeComponent();
            Application.AddMessageFilter(this);
        }

        public bool PreFilterMessage(ref Message m)
        {
            if (m.Msg == 0x20a)
            {
                // WM_MOUSEWHEEL, find the control at screen position m.LParam
                Point pos = new Point(m.LParam.ToInt32() & 0xffff, m.LParam.ToInt32() >> 16);
                IntPtr hWnd = WindowFromPoint(pos);
                if (hWnd != IntPtr.Zero && hWnd != m.HWnd && Control.FromHandle(hWnd) != null)
                {
                    //取得控制項
                    ScrollableControl ctrl = Control.FromHandle(hWnd) as ScrollableControl;
                    int orgValue = 0;
                    if (ctrl != null)
                    {
                        //取得控制項垂直ScrollBar的值
                        orgValue = ctrl.VerticalScroll.Value;
                    }
                    SendMessage(hWnd, m.Msg, m.WParam, m.LParam);
                    if (ctrl != null)
                    {
                        //取得控制項垂直ScrollBar的值
                        int newValue = ctrl.VerticalScroll.Value;
                        var se = new ScrollEventArgs(ScrollEventType.ThumbTrack, orgValue, newValue
                            , ScrollOrientation.VerticalScroll);
                        FireScrollEvent(ctrl, se);
                    }
                    return true;
                }
            }
            return false;
        }

        /// <summary>
        /// 觸發控制項的Scroll事件
        /// </summary>
        /// <param name="sc"></param>
        /// <param name="e"></param>
        private void FireScrollEvent(ScrollableControl sc, ScrollEventArgs e)
        {
            MethodInfo onScroll = sc.GetType().GetMethod("OnScroll",
                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
            onScroll.Invoke(sc, new object[] { e });
        }
    }
}