在C#应用程序中,全局键盘捕获是指在操作系统层面捕获键盘事件,而不仅仅是在应用程序窗口内。这使得应用程序可以在用户按下键盘按键时收到通知,即使应用程序没有处于活动状态。全局键盘捕获在某些情况下非常有用,例如,用户可以通过按下特定的组合键来启动应用程序。
要在C#应用程序中实现全局键盘捕获,可以使用低级键盘钩子。低级键盘钩子是一种操作系统层面的机制,允许应用程序在系统级别拦截和处理键盘事件。在C#中,可以使用SetWindowsHookEx
函数和WH_KEYBOARD_LL
钩子类型来实现全局键盘捕获。
以下是一个简单的示例,演示如何在C#应用程序中实现全局键盘捕获:
using System;
using System.Runtime.InteropServices;
public class GlobalKeyboardHook
{
private const int WH_KEYBOARD_LL = 13;
private const int WM_KEYDOWN = 0x0100;
private const int WM_KEYUP = 0x0101;
private const int WM_SYSKEYDOWN = 0x0104;
private const int WM_SYSKEYUP = 0x0105;
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool UnhookWindowsHookEx(IntPtr hhk);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr GetModuleHandle(string lpModuleName);
public delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);
public event EventHandler<KeyEventArgs> KeyDown;
public event EventHandler<KeyEventArgs> KeyUp;
private IntPtr _hookId = IntPtr.Zero;
private LowLevelKeyboardProc _proc;
public GlobalKeyboardHook()
{
_proc = HookCallback;
}
public void Start()
{
if (_hookId == IntPtr.Zero)
{
_hookId = SetWindowsHookEx(WH_KEYBOARD_LL, _proc, GetModuleHandle(null), 0);
}
}
public void Stop()
{
if (_hookId != IntPtr.Zero)
{
UnhookWindowsHookEx(_hookId);
_hookId = IntPtr.Zero;
}
}
private IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
{
if (nCode >= 0)
{
int vkCode = Marshal.ReadInt32(lParam);
bool isKeyDown = wParam == (IntPtr)WM_KEYDOWN || wParam == (IntPtr)WM_SYSKEYDOWN;
bool isKeyUp = wParam == (IntPtr)WM_KEYUP || wParam == (IntPtr)WM_SYSKEYUP;
if (isKeyDown || isKeyUp)
{
var keyArgs = new KeyEventArgs(vkCode, isKeyDown);
if (isKeyDown)
{
KeyDown?.Invoke(this, keyArgs);
}
else
{
KeyUp?.Invoke(this, keyArgs);
}
if (keyArgs.Handled)
{
return (IntPtr)1;
}
}
}
return CallNextHookEx(_hookId, nCode, wParam, lParam);
}
}
public class KeyEventArgs : EventArgs
{
public int VkCode { get; }
public bool IsKeyDown { get; }
public bool Handled { get; set; }
public KeyEventArgs(int vkCode, bool isKeyDown)
{
VkCode = vkCode;
IsKeyDown = isKeyDown;
}
}
在上面的示例中,GlobalKeyboardHook
类实现了全局键盘捕获,并通过KeyDown
和KeyUp
事件提供了键盘按键事件。要使用此类,只需创建一个GlobalKeyboardHook
实例,并订阅KeyDown
和KeyUp
事件即可。
需要注意的是,全局键盘捕获可能会影响系统性能,因此应谨慎使用。此外,在使用全局键盘捕获时,应确保遵循操作系统的安全策略,以避免安全风险。
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