我正在编写一个简单的C#应用程序，我需要在Listview上使用onScroll事件。因此，我创建了一个继承原始ListView的ListviewEx类。我找到了如何从WinAPI中检测滚动消息，并修改了WndProc方法。
现在我有了这个WndProc：
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
if (m.Msg == WM_VSCROLL)
{
onScroll(this, new EventArgs());
}
}
但问题是，我不知道如何检测有关滚动的信息。此数据应该在WParam中，但在C＃中没有像C ++中的LOWORD宏，我需要使用switch来检测诸如SB_BOTTOM、SB_ENDSCROLL、SB_PAGEUP等参数。
是否有任何方法可以在C＃中替换LOWORD宏？
或者其他方法如何检测滚动所需的参数？
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using Microsoft.Win32;
using System.Reflection;
namespace ControlsEx
{
public class ListViewEx : ListView
{
// Windows messages
private const int WM_PAINT = 0x000F;
private const int WM_HSCROLL = 0x0114;
private const int WM_VSCROLL = 0x0115;
private const int WM_MOUSEWHEEL = 0x020A;
private const int WM_KEYDOWN = 0x0100;
private const int WM_LBUTTONUP = 0x0202;
// ScrollBar types
private const int SB_HORZ = 0;
private const int SB_VERT = 1;
// ScrollBar interfaces
private const int SIF_TRACKPOS = 0x10;
private const int SIF_RANGE = 0x01;
private const int SIF_POS = 0x04;
private const int SIF_PAGE = 0x02;
private const int SIF_ALL = SIF_RANGE | SIF_PAGE | SIF_POS | SIF_TRACKPOS;
// ListView messages
private const uint LVM_SCROLL = 0x1014;
private const int LVM_FIRST = 0x1000;
private const int LVM_SETGROUPINFO = (LVM_FIRST + 147);
public enum ScrollBarCommands : int
{
SB_LINEUP = 0,
SB_LINELEFT = 0,
SB_LINEDOWN = 1,
SB_LINERIGHT = 1,
SB_PAGEUP = 2,
SB_PAGELEFT = 2,
SB_PAGEDOWN = 3,
SB_PAGERIGHT = 3,
SB_THUMBPOSITION = 4,
SB_THUMBTRACK = 5,
SB_TOP = 6,
SB_LEFT = 6,
SB_BOTTOM = 7,
SB_RIGHT = 7,
SB_ENDSCROLL = 8
}
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
switch(m.Msg)
{
case WM_VSCROLL:
ScrollEventArgs sargs = new ScrollEventArgs(ScrollEventType.EndScroll, GetScrollPos(this.Handle, SB_VERT));
onScroll(this, sargs);
break;
case WM_MOUSEWHEEL:
ScrollEventArgs sarg = new ScrollEventArgs(ScrollEventType.EndScroll, GetScrollPos(this.Handle, SB_VERT));
onScroll(this, sarg);
break;
case WM_KEYDOWN:
switch (m.WParam.ToInt32())
{
case (int)Keys.Down:
onScroll(this, new ScrollEventArgs(ScrollEventType.SmallDecrement, GetScrollPos(this.Handle, SB_VERT)));
break;
case (int)Keys.Up:
onScroll(this, new ScrollEventArgs(ScrollEventType.SmallIncrement, GetScrollPos(this.Handle, SB_VERT)));
break;
case (int)Keys.PageDown:
onScroll(this, new ScrollEventArgs(ScrollEventType.LargeDecrement, GetScrollPos(this.Handle, SB_VERT)));
break;
case (int)Keys.PageUp:
onScroll(this, new ScrollEventArgs(ScrollEventType.LargeIncrement, GetScrollPos(this.Handle, SB_VERT)));
break;
case (int)Keys.Home:
onScroll(this, new ScrollEventArgs(ScrollEventType.First, GetScrollPos(this.Handle, SB_VERT)));
break;
case (int)Keys.End:
onScroll(this, new ScrollEventArgs(ScrollEventType.Last, GetScrollPos(this.Handle, SB_VERT)));
break;
}
break;
}
}
public int ScrollPosition
{
get
{
return GetScrollPos(this.Handle, SB_VERT);
}
set
{
int prevPos;
int scrollVal;
if (ShowGroups == true)
{
prevPos = GetScrollPos(this.Handle, SB_VERT);
scrollVal = -(prevPos - value);
}
else
{
// TODO: Add setScrollPosition if ShowGroups == false
}
SendMessage(this.Handle, LVM_SCROLL, (IntPtr)0, (IntPtr)scrollVal);
}
}
public event ScrollEventHandler onScroll;
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool GetScrollInfo(IntPtr hwnd, int fnBar, ref SCROLLINFO lpsi);
[DllImport("user32.dll")]
public static extern int SendMessage(
int hWnd, // handle to destination window
uint Msg, // message
long wParam, // first message parameter
long lParam // second message parameter
);
[DllImport("user32.dll")]
static extern int SendMessage(IntPtr hWnd, int wMsg,
int wParam, int lParam);
[DllImport("user32.dll")]
static extern int SendMessage(IntPtr hWnd, uint wMsg,
IntPtr wParam, IntPtr lParam);
[DllImport("user32.dll")]
static extern int SetScrollPos(IntPtr hWnd, int nBar, int nPos, bool bRedraw);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern int GetScrollPos(IntPtr hWnd, int nBar);
[StructLayout(LayoutKind.Sequential)]
struct SCROLLINFO
{
public uint cbSize;
public uint fMask;
public int nMin;
public int nMax;
public uint nPage;
public int nPos;
public int nTrackPos;
}
}
}
您可以定义WParam常量如下：
private const int WM_HSCROLL = 0x114;
private const int WM_VSCROLL = 0x115;
private const int SB_HORZ = 0;
private const int SB_VERT = 1;
private const int SB_LINELEFT = 0;
private const int SB_LINERIGHT = 1;
private const int SB_PAGELEFT = 2;
private const int SB_PAGERIGHT = 3;
private const int SB_THUMBPOSITION = 4;
private const int SB_THUMBTRACK = 5;
private const int SB_LEFT = 6;
private const int SB_RIGHT = 7;
private const int SB_ENDSCROLL = 8;
private const int SIF_TRACKPOS = 0x10;
private const int SIF_RANGE = 0x1;
private const int SIF_POS = 0x4;
private const int SIF_PAGE = 0x2;
private const int SIF_ALL = SIF_RANGE | SIF_PAGE | SIF_POS | SIF_TRACKPOS;
检查WParam的实际代码可能是这样的：
if (m.Msg == WM_VSCROLL)
{
ScrollInfoStruct si = new ScrollInfoStruct();
si.fMask = SIF_ALL;
si.cbSize = (uint)Marshal.SizeOf(si);
GetScrollInfo(msg.HWnd, SB_VERT, ref si);
if (msg.WParam.ToInt32() == SB_ENDSCROLL)
{
ScrollEventArgs sargs = new ScrollEventArgs(ScrollEventType.EndScroll, si.nPos);
onScroll(this, sargs);
}
}
pinvoke.net是一个很好的网站，可以获取使用Windows 32 API中常量值，而无需自己检查头文件。
Martijn提供的答案是可行的，但不能捕获所有滚动。只有当用户直接操纵滚动条时才会发送WM_VSCROLL消息。如果用户使用鼠标滚轮滚动或使用UpArrow / DownArrow / PageUp / PageDown键进行滚动，则不会发送WM_VSCROLL。
您可以通过侦听LVN_BEGINSCROLL通知消息来捕获由滚动条和鼠标滚轮引起的滚动。
捕获使用键时发生的滚动更难。例如，在响应PageUp键时，不会向控件发送任何消息。在这种情况下，最好的做法是侦听KeyPress事件，然后在事件之前和之后检查滚动条位置是否有变化。
当然，对于您的目的而言，这可能完全无关紧要。WM_VSCROLL消息可能已经足够了。但是，如果您想捕获所有可能的滚动，请查看ObjectListView中的代码，该代码已经具有捕获所有这些可能性的Scroll事件。
@Klinki
感谢您的出色贡献 我认为您忘记处理水平滚动了
Case WM_HSCROLL
Dim sargs As New ScrollEventArgs(ScrollEventType.EndScroll, GetScrollPos(Me.Handle, SB_HORZ))
RaiseEvent OnScroll(Me, sargs)
Exit Select