C#下usb条码扫描枪的钩子实现的改进

  【目前的条形码扫描器有点类似外接键盘（其实从消息传送上它就相当于一个键盘），把输入焦点定位到可输入的控件上，一扫描相应的条形码信息就输入到文本框中去了，但是如果没有输入焦点，或另一个不相干的程序获得输入焦点，那就有点乱套了。我想实现的是，不管什么情况，只要扫描器一工作，我的程序就能自动激活，并能获得当前输入的条形码信息。 实现思路：我用的是litele牌的USB口的红外条形码扫描器，仔细分析了一下，扫描成功后，以键盘按键消息的形式把条形码输入信息通知给系统。这样通过键盘钩子就可以方便的获得该信息了。但是，怎样区分信息是键盘还是条形码输入的哪？很简单，条形码扫描器在很短的时间内输入了至少3个字符以上信息，并且以“回车”作为结束字符，在这种思想指引下，很完美的实现了预定功能。】

frmMain:

public BarCodeHook BarCode = new BarCodeHook();
public delegate void ShowInfoDelegate(BarCodeHook.BarCodes barCode);
void ShowInfo(BarCodeHook.BarCodes barCode){
textBox_barCode.Text = barCode.BarCode;
buttonX2.Focus();
}
public void BarCode_BarCodeEvent(BarCodeHook.BarCodes barCode)
{
ShowInfo(barCode);
}

public frmMain()
{
InitializeComponent();
BarCode.BarCodeEvent += new BarCodeHook.BarCodeDelegate(BarCode_BarCodeEvent);

}
如果焦点本来就在textBox上，会产生多余的字符，所以在showInfo函数里，每次都手动让buttonX2成为焦点。

public class BarCodeHook
{
public delegate void BarCodeDelegate(BarCodes barCode);
public event BarCodeDelegate BarCodeEvent;

public struct BarCodes
{
public int VirtKey;      //虚拟码
public int ScanCode;     //扫描码
public string KeyName;   //键名
public uint AscII;       //AscII
public char Chr;         //字符

public string BarCode;   //条码信息
public bool IsValid;     //条码是否有效
public DateTime Time;    //扫描时间
}

private struct EventMsg
{
public int message;
public int paramL;
public int paramH;
public int Time;
public int hwnd;
}

[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
private static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
private static extern bool UnhookWindowsHookEx(int idHook);

[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
private static extern int CallNextHookEx(int idHook, int nCode, Int32 wParam, IntPtr lParam);

[DllImport("user32", EntryPoint = "GetKeyNameText")]
private static extern int GetKeyNameText(int lParam, StringBuilder lpBuffer, int nSize);

[DllImport("user32", EntryPoint = "GetKeyboardState")]
private static extern int GetKeyboardState(byte[] pbKeyState);

[DllImport("user32", EntryPoint = "ToAscii")]
private static extern bool ToAscii(int VirtualKey, int ScanCode, byte[] lpKeyState, ref uint lpChar, int uFlags);

delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);
BarCodes barCode = new BarCodes();
int hKeyboardHook = 0;
public string strBarCode = "";
public int length;

private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
{
barCode.IsValid = false;
bool notChar = false;
if (nCode == 0)
{
EventMsg msg = (EventMsg)Marshal.PtrToStructure(lParam, typeof(EventMsg));

if (wParam == 0x100)   //WM_KEYDOWN = 0x100
{
barCode.VirtKey = msg.message & 0xff;  //虚拟码
barCode.ScanCode = msg.paramL & 0xff;  //扫描码

StringBuilder strKeyName = new StringBuilder(255);
if (GetKeyNameText(barCode.ScanCode * 65536, strKeyName, 255) > 0)
{
barCode.KeyName = strKeyName.ToString().Trim(new char[] { ' ', '\0' });
}
else
{
barCode.KeyName = "";
}

byte[] kbArray = new byte[256];
uint uKey = 0;
GetKeyboardState(kbArray);
if (ToAscii(barCode.VirtKey, barCode.ScanCode, kbArray, ref uKey, 0))
{
barCode.AscII = uKey;
barCode.Chr = Convert.ToChar(uKey);
}
else
{
notChar = true;   //转到ascii字符失败，这不是一个正常字符，要去掉
}

if (DateTime.Now.Subtract(barCode.Time).TotalMilliseconds > 30)     //30ms可以过滤掉连续按住一个键时的情况
{
if (notChar == false)
strBarCode = barCode.Chr.ToString();
else
strBarCode = "";
barCode.IsValid = false;
}
else
{
if (strBarCode.Length >= 5)
{
barCode.IsValid = true;      //isValid为true表明这是个条码
}
if (notChar == false)
{
strBarCode += barCode.Chr.ToString();
}
barCode.BarCode = strBarCode;
}

barCode.Time = DateTime.Now;
if (BarCodeEvent != null && barCode.IsValid) BarCodeEvent(barCode);    //触发事件

}
}
return CallNextHookEx(hKeyboardHook, nCode, wParam, lParam);
}

// 安装钩子
public bool Start()
{
if (hKeyboardHook == 0)
{
//WH_KEYBOARD_LL = 13
hKeyboardHook = SetWindowsHookEx(13, new HookProc(KeyboardHookProc), Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]), 0);
}
return (hKeyboardHook != 0);
}

// 卸载钩子
public bool Stop()
{
if (hKeyboardHook != 0)
{
bool result = UnhookWindowsHookEx(hKeyboardHook);
hKeyboardHook = 0;         //将hKeyboardHook 置为0
if (result)
{

//MessageBox.Show("true");
}
return result;
}

return true;
}
}

是如果扫到的是英文字符的话，会有一个多余的码无法从键盘码转到ascii码，需要去掉这个码。同时设为30ms可以过滤掉一直按住一个键的情况。