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在程序中捕捉用户的按键行为很容易，但是假如程序最小化了或者隐藏到系统托盘了，这时因为程序已经失去焦点了我们想捕捉按键行为就不是那么容易了。怎么办呢？这就要使用键盘钩子了。
关于键盘钩子，下面这个网友描述的很详尽，我就不班门弄斧了，转载过来以备不时之需。原文：http://www.cnblogs.com/hocylan/archive/2008/01/14/1038390.html
一概要
1 目的：完成简单的监控和屏蔽
2 技术：钩子（系统监控必须全局钩子）
3 步骤：
A 安装钩子
B 回调函数
C 处理函数
D 普通业务处理
……
4 完成
下载源程序和运行程序
http://files.cnblogs.com/hocylan/KeyboardHook.rar
运行界面如下：
二说明：
在C++中实现该功能十分简单，也有很多经典例子可以实现，在C#中确有很多问题会出现。
对于钩子知识不太熟悉可以参考我转载的另一篇文章：http://www.cnblogs.com/hocylan/articles/1033895.html[微软HOOK技术专题]
三大概步骤
其实主要就是调用windows API
第一步：安装钩子：SetWindowsHookEx(WH_Codes idHook, HookProc lpfn,IntPtr pInstance, int threadId);
第二步：回调和处理 CallNextHookEx(IntPtr pHookHandle, int nCode,Int32 wParam, IntPtr lParam);
第三步：完成普通的业务处理其它流程
将封装的钩子应用到系统中…….
private void start_Click(object sender, EventArgs e)
{ hook_Main.InstallHook("1");}
private void stop_Click(object sender, EventArgs e)
{this.hook_Main.UnInstallHook();}
private void stopkeyboard_Click(object sender, EventArgs e)
{ hook_Main.InstallHook("2"); }
第四步：拆卸钩子UnhookWindowsHookEx(IntPtr pHookHandle);
四 重要代码和解释：
*封装的hook类：
using System;
using System.Windows.Forms;
using System.Runtime.InteropServices; //必须引用
using System.Reflection; //必须引用
namespace KeyboardHook
{
class Hocy_Hook
{
#region私有常量
///<summary>
///按键状态数组
///</summary>
private readonly byte[] m_KeyState = new byte[ 256 ];
private string flags;
//flag=0 正常 flag=1 监控状态 flag=2 屏蔽键盘//
#endregion私有常量
#region私有变量
///<summary>
///鼠标钩子句柄
///</summary>
private IntPtr m_pMouseHook = IntPtr.Zero;
///<summary>
///键盘钩子句柄
///</summary>
private IntPtr m_pKeyboardHook = IntPtr.Zero;
///<summary>
///鼠标钩子委托实例
///</summary>
///<remarks>
///不要试图省略此变量,否则将会导致
///激活CallbackOnCollectedDelegate 托管调试助手(MDA)。
///详细请参见MSDN中关于CallbackOnCollectedDelegate 的描述
///</remarks>
private HookProc m_MouseHookProcedure;
///<summary>
///键盘钩子委托实例
///</summary>
///<remarks>
///不要试图省略此变量,否则将会导致
///激活CallbackOnCollectedDelegate 托管调试助手(MDA)。
///详细请参见MSDN中关于CallbackOnCollectedDelegate 的描述
///</remarks>
private HookProc m_KeyboardHookProcedure;
// 添加
public event MouseEventHandler OnMouseActivity;
private const byte VK_SHIFT = 0x10 ;
private const byte VK_CAPITAL = 0x14;
private const byte VK_NUMLOCK = 0x90;
#endregion私有变量
#region事件定义
///<summary>
///鼠标更新事件
///</summary>
///<remarks>当鼠标移动或者滚轮滚动时触发</remarks>
public event MouseUpdateEventHandler OnMouseUpdate;
///<summary>
///按键按下事件
///</summary>
public event KeyEventHandler OnKeyDown;
///<summary>
///按键按下并释放事件
///</summary>
public event KeyPressEventHandler OnKeyPress;
///<summary>
///按键释放事件
///</summary>
public event KeyEventHandler OnKeyUp;
#endregion事件定义
#region私有方法
///<summary>
///鼠标钩子处理函数
///</summary>
///<param name="nCode"></param>
///<param name="wParam"></param>
///<param name="lParam"></param>
///<returns>鼠标钩子处理函数</returns>
private int MouseHookProc( int nCode, Int32 wParam, IntPtr lParam )
{
if ((nCode >= 0) && (OnMouseActivity != null))
{
//Marshall the data from callback.
MouseHookStruct mouseHookStruct = (MouseHookStruct)Marshal.PtrToStructure(lParam, typeof(MouseHookStruct));
//detect button clicked
MouseButtons button = MouseButtons.None;
short mouseDelta = 0;
switch (wParam)
{
case (int)WM_MOUSE.WM_LBUTTONDOWN:
//case WM_LBUTTONUP:
//case WM_LBUTTONDBLCLK:
button = MouseButtons.Left;
break;
case (int)WM_MOUSE.WM_RBUTTONDOWN:
//case WM_RBUTTONUP:
//case WM_RBUTTONDBLCLK:
button = MouseButtons.Right;
break;
case (int)WM_MOUSE.WM_MOUSEWHEEL:
//If the message is WM_MOUSEWHEEL, the high-order word of mouseData member is the wheel delta.
//One wheel click is defined as WHEEL_DELTA, which is 120.
//(value >> 16) & 0xffff; retrieves the high-order word from the given 32-bit value
mouseDelta = (short)((mouseHookStruct.MouseData>> 16) & 0xffff);
//TODO: X BUTTONS (I havent them so was unable to test)
//If the message is WM_XBUTTONDOWN, WM_XBUTTONUP, WM_XBUTTONDBLCLK, WM_NCXBUTTONDOWN, WM_NCXBUTTONUP,
//or WM_NCXBUTTONDBLCLK, the high-order word specifies which X button was pressed or released,
//and the low-order word is reserved. This value can be one or more of the following values.
//Otherwise, mouseData is not used.
break;
}
//double clicks
int clickCount = 0;
if (button != MouseButtons.None)
if (wParam == (int)WM_MOUSE.WM_LBUTTONDBLCLK || wParam == (int)WM_MOUSE.WM_RBUTTONDBLCLK) clickCount = 2;
else clickCount = 1;
//generate event
MouseEventArgs e = new MouseEventArgs(
button,
clickCount,
mouseHookStruct.Point.X,
mouseHookStruct.Point.Y,
mouseDelta);
//raise it
OnMouseActivity(this, e);
}
//*
return Win32API.CallNextHookEx( this.m_pMouseHook, nCode, wParam, lParam );
}
///<summary>
///键盘钩子处理函数
///</summary>
///<param name="nCode"></param>
///<param name="wParam"></param>
///<param name="lParam"></param>
///<returns></returns>
///<remarks></remarks>
private int KeyboardHookProc( int nCode, Int32 wParam, IntPtr lParam )
{
switch (flags)
{
case "2":
return 1;
break;
case "1":
break;
}
bool handled = false;
//it was ok and someone listens to events
if ((nCode >= 0) && (this.OnKeyDown != null || this.OnKeyUp!= null || this.OnKeyPress!= null))
{
//read structure KeyboardHookStruct at lParam
KeyboardHookStruct MyKeyboardHookStruct = (KeyboardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyboardHookStruct));
//raise KeyDown
if (this.OnKeyDown != null && (wParam == (int)WM_KEYBOARD.WM_KEYDOWN || wParam == (int)WM_KEYBOARD.WM_SYSKEYDOWN))
{
Keys keyData = (Keys)MyKeyboardHookStruct.VKCode;
KeyEventArgs e = new KeyEventArgs(keyData);
this.OnKeyDown(this, e);
handled = handled || e.Handled;
}
// raise KeyPress
if (this.OnKeyPress != null && wParam == (int)WM_KEYBOARD.WM_KEYDOWN)
{
bool isDownShift, isDownCapslock;
try
{
isDownShift = ((Win32API.GetKeyStates(VK_SHIFT) & 0x80) == 0x80 ? true : false);
isDownCapslock = (Win32API.GetKeyStates(VK_CAPITAL) != 0 ? true : false);
}
catch
{
isDownCapslock = false;
isDownShift= false;
}
byte[] keyState = new byte[256];
Win32API.GetKeyboardState(keyState);
byte[] inBuffer = new byte[2];
if (Win32API.ToAscii(MyKeyboardHookStruct.VKCode,
MyKeyboardHookStruct.ScanCode,
keyState,
inBuffer,
MyKeyboardHookStruct.Flags) == 1)
{
char key = (char)inBuffer[0];
if ((isDownCapslock ^ isDownShift) && Char.IsLetter(key)) key = Char.ToUpper(key);
KeyPressEventArgs e = new KeyPressEventArgs(key);
this.OnKeyPress(this, e);
handled = handled || e.Handled;
}
}
// raise KeyUp
if (this.OnKeyUp != null && (wParam == (int)WM_KEYBOARD.WM_KEYUP || wParam == (int)WM_KEYBOARD.WM_SYSKEYUP))
{
Keys keyData = (Keys)MyKeyboardHookStruct.VKCode;
KeyEventArgs e = new KeyEventArgs(keyData);
this.OnKeyUp(this, e);
handled = handled || e.Handled;
}
}
//if event handled in application do not handoff to other listeners
if (handled)
return 1;
else
return Win32API.CallNextHookEx(this.m_pKeyboardHook, nCode, wParam, lParam);
}
#endregion私有方法
#region公共方法
///<summary>
///安装钩子
///</summary>
///<returns></returns>
public bool InstallHook(string flagsinfo)
{
this.flags = flagsinfo;
IntPtr pInstance = Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().ManifestModule);
//pInstance = (IntPtr)4194304;
//注意：很多时候得到的pInstanc无法安装钩子，请检查值是否为4194304，在应用程序中可以直接取得pinstance的
// IntPtr pInstanc2 = Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly());
// Assembly.GetExecutingAssembly().GetModules()[0]
//安装鼠标钩子
if ( this.m_pMouseHook == IntPtr.Zero )
{
this.m_MouseHookProcedure = new HookProc( this.MouseHookProc );
this.m_pMouseHook = Win32API.SetWindowsHookEx( WH_Codes.WH_MOUSE_LL,this.m_MouseHookProcedure, pInstance, 0 );
// WH_Codes.WH_MOUSE_LL为全局钩子即系统钩子，否则应该为WH_Codes.WH_KEYBOARD，即普通钩子
if ( this.m_pMouseHook == IntPtr.Zero )
{
this.UnInstallHook();
return false;
}
}
if ( this.m_pKeyboardHook == IntPtr.Zero ) //安装键盘钩子
{
this.m_KeyboardHookProcedure = new HookProc( this.KeyboardHookProc );
// WH_Codes.WH_KEYBOARD_LL为全局钩子即系统钩子，否则应该为WH_Codes.WH_KEYBOARD，即普通钩子
this.m_pKeyboardHook = Win32API.SetWindowsHookEx( WH_Codes.WH_KEYBOARD_LL,this.m_KeyboardHookProcedure, pInstance, 0 );
if ( this.m_pKeyboardHook == IntPtr.Zero )
{
this.UnInstallHook();
return false;
}
}
return true;
}
///<summary>
///卸载钩子
///</summary>
///<returns></returns>
public bool UnInstallHook()
{
bool result = true;
if ( this.m_pMouseHook != IntPtr.Zero )
{
result = ( Win32API.UnhookWindowsHookEx( this.m_pMouseHook ) && result );
this.m_pMouseHook = IntPtr.Zero;
}
if ( this.m_pKeyboardHook != IntPtr.Zero )
{
result = ( Win32API.UnhookWindowsHookEx( this.m_pKeyboardHook ) && result );
this.m_pKeyboardHook = IntPtr.Zero;
}
return result;
}
#endregion公共方法
#region构造函数
///<summary>
///钩子类
///</summary>
///<remarks>本类仅仅简单实现了WH_KEYBOARD_LL 以及WH_MOUSE_LL </remarks>
public Hocy_Hook()
{
Win32API.GetKeyboardState( this.m_KeyState );
}
#endregion构造函数
}
}
另外感谢来自Germany的George Mamaladze，看了他的代码，给了我比较好的思路
http://www.codeproject.com/KB/cs/globalhook.aspx
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