淨鍵盤鉤子額外KeyUp事件

Question

我有業務需求，對於消息框，用戶不能按回車鍵接受默認選項，但按選擇的關鍵。例如。給定一個帶有選項Yes/No的MessageBox，用戶必須按下Y或N鍵。現在我實現了這個使用以下鍵盤鉤子，但是當代碼返回，KeyUp事件也得到返回到調用代碼。

所以，問題是：如何返回到調用代碼之前刷新所有的鍵盤事件？

我已經刪除鍋爐板代碼，但如果你需要它，請告知。

調用代碼：

private static ResultMsgBox MsgResultBaseNoEnter(string msg, string caption, uint options) 
    { 
     ResultMsgBox res; 
     _hookID = SetHook(_proc); 
     try 
     { 
      res = MessageBox(GetForegroundWindow(), msg, caption, options); 
     } 
     finally 
     { 
      UnhookWindowsHookEx(_hookID); 
     } 
     return res; 
    } 

和鉤代碼：

private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam) 
    { 
     if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN) 
     { 
      int vkCode = Marshal.ReadInt32(lParam); 
      if (vkCode == VK_RETURN) 
       return (IntPtr)(-1); 
     } 
     return CallNextHookEx(_hookID, nCode, wParam, lParam); 
    } 

Answer 1

添加幾行代碼在類的地方（或可通過其他類使用的一些靜態類）：

[StructLayout(LayoutKind.Sequential)] 
public class MSG 
{ 
    public IntPtr hwnd; 
    public uint message; 
    public IntPtr wParam; 
    public IntPtr lParam; 
    public uint time; 
    int x; 
    int y; 
} 

[DllImport("user32")] 
public static extern bool PeekMessage([Out]MSG lpMsg, IntPtr hWnd, uint wMsgFilterMin, uint wMsgFilterMax, int wRemoveMsg); 

/// <summary> 
/// Examines the message queue for key messages. 
/// </summary> 
/// <param name="remove">If this parameter is true, the returned message is also removed from the queue.</param> 
/// <returns>Returns the next available key message, or null if there is no key message available.</returns> 
public static MSG PeekKeyMessage(bool remove) 
{ 
    MSG msg = new MSG(); 
    if (PeekMessage(msg, IntPtr.Zero, 0x0100 /*WM_KEYFIRST*/, 0x0109 /*WM_KEYLAST*/, remove ? 1 : 0)) 
     return msg; 
    return null; 
} 

public static void RemoveAllKeyMessages() 
{ 
    while (PeekKeyMessage(true) != null) ; // Empty body. Every call to the method removes one key message. 
} 

調用RemoveAllKeyMessages()不正是你想要的。

Answer 2

其實你可以不刷新鍵盤事件，但可以防止該事件由線程的消息被接收循環。
您應該安裝一個處理程序WH_GETMESSAGE掛鉤。鉤子程序的lParam是指向MSG結構的指針。在檢查結構之後，您可以更改它以避免將消息傳遞給呼叫消息處理器。您應該將消息更改爲WM_NULL。
在.NET實際的過程有點長的，需要一個單獨的文章。但是，簡單地說，這裏是如何：

拷貝類完全一樣就是在項目中的一個新的C＃文件：

using System; 
using System.Collections.Generic; 
using System.Diagnostics; 
using System.Runtime.InteropServices; 

namespace Unicorn 
{ 
    public static class HookManager 
    { 
     #region Fields 

     private delegate int HookDelegate(int ncode, IntPtr wParam, IntPtr lParam); 
     private static HookDelegate getMessageHookProc; 
     private static IntPtr getMessageHookHandle; 
     private static List<EventHandler<GetMessageHookEventArgs>> getMessageHandlers = 
      new List<EventHandler<GetMessageHookEventArgs>>(); 

     #endregion 
     #region Private Methods - Installation and Uninstallation 

     private static void InstallGetMessageHook() 
     { 
      if (getMessageHookProc != null) 
       return; 
      getMessageHookProc = new HookDelegate(GetMessageHookProc); 
      getMessageHookHandle = SetWindowsHookEx(WH_GETMESSAGE, getMessageHookProc, 0, GetCurrentThreadId()); 
     } 

     private static void UninstallGetMessageHook() 
     { 
      if (getMessageHookProc == null) 
       return; 
      UnhookWindowsHookEx(getMessageHookHandle); 
      getMessageHookHandle = IntPtr.Zero; 
      getMessageHookProc = null; 
     } 

     #endregion 
     #region Public Methods - Add and Remove Handlers 

     public static void AddGetMessageHookHandler(EventHandler<GetMessageHookEventArgs> handler) 
     { 
      if (getMessageHandlers.Contains(handler)) 
       return; 
      getMessageHandlers.Add(handler); 
      if (getMessageHandlers.Count == 1) 
       InstallGetMessageHook(); 
     } 

     public static void RemoveGetMessageHookHandler(EventHandler<GetMessageHookEventArgs> handler) 
     { 
      getMessageHandlers.Remove(handler); 
      if (getMessageHandlers.Count == 0) 
       UninstallGetMessageHook(); 
     } 

     #endregion 
     #region Private Methods - Hook Procedures 

     [DebuggerStepThrough] 
     private static int GetMessageHookProc(int code, IntPtr wParam, IntPtr lParam) 
     { 
      if (code == 0) // HC_ACTION 
      { 
       MSG msg = new MSG(); 
       Marshal.PtrToStructure(lParam, msg); 
       GetMessageHookEventArgs e = new GetMessageHookEventArgs() 
       { 
        HWnd = msg.hwnd, 
        Msg = msg.message, 
        WParam = msg.wParam, 
        LParam = msg.lParam, 
        MessageRemoved = (int)wParam == 1, 
        ShouldApplyChanges = false 
       }; 

       foreach (var handler in getMessageHandlers.ToArray()) 
       { 
        handler(null, e); 
        if (e.ShouldApplyChanges) 
        { 
         msg.hwnd = e.HWnd; 
         msg.message = e.Msg; 
         msg.wParam = e.WParam; 
         msg.lParam = e.LParam; 
         Marshal.StructureToPtr(msg, (IntPtr)lParam, false); 
         e.ShouldApplyChanges = false; 
        } 
       } 
      } 

      return CallNextHookEx(getMessageHookHandle, code, wParam, lParam); 
     } 

     #endregion 
     #region Win32 stuff 

     private const int WH_KEYBOARD = 2; 
     private const int WH_GETMESSAGE = 3; 
     private const int WH_CALLWNDPROC = 4; 
     private const int WH_MOUSE = 7; 
     private const int WH_CALLWNDPROCRET = 12; 

     [StructLayout(LayoutKind.Sequential)] 
     public class MSG 
     { 
      public IntPtr hwnd; 
      public uint message; 
      public IntPtr wParam; 
      public IntPtr lParam; 
      public uint time; 
      int x; 
      int y; 
     } 


     [DllImport("USER32.dll", CharSet = CharSet.Auto)] 
     private static extern IntPtr SetWindowsHookEx(int idHook, HookDelegate lpfn, int hMod, int dwThreadId); 

     [DllImport("USER32.dll", CharSet = CharSet.Auto)] 
     private static extern int CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam); 

     [DllImport("USER32.dll", CharSet = CharSet.Auto)] 
     private static extern bool UnhookWindowsHookEx(IntPtr hhk); 

     [DllImport("kernel32.dll", ExactSpelling = true, CharSet = CharSet.Auto)] 
     private static extern int GetCurrentThreadId(); 
     #endregion 
    } 

    #region EventArgs 

    public class GetMessageHookEventArgs : EventArgs 
    { 
     public uint Msg { get; set; } 
     public IntPtr HWnd { get; set; } 
     public IntPtr WParam { get; set; } 
     public IntPtr LParam { get; set; } 

     public bool MessageRemoved { get; set; } 
     public bool ShouldApplyChanges { get; set; } 
    } 

    #endregion 
} 

這是一個輔助類，做你所需要的。我的實際類稍微長一些，可以處理更多的鉤子類型，但是我清除了代碼以使其更小。

在此之後，你的代碼應該是這樣的：

private static void GetMessageProcHook(object sender, Unicorn.GetMessageHookEventArgs e) 
{ 
    if (e.Msg == 0x100 && (Keys)e.WParam == Keys.Return) // WM_KEYDOWN 
    { 
     // swallow the message 
     e.Msg = 0; // WM_NULL 
     e.WParam = IntPtr.Zero; 
     e.LParam = IntPtr.Zero; 
     e.ShouldApplyChanges = true; // This will tell the HookManager to copy the changes back. 
    } 
} 

private static ResultMsgBox MsgResultBaseNoEnter(string msg, string caption, uint options) 
{ 
    ResultMsgBox res; 
    Unicorn.HookManager.AddGetMessageHookHandler(GetMessageProcHook); 
    try 
    { 
     res = MessageBox(GetForegroundWindow(), msg, caption, options); 
    } 
    finally 
    { 
     Unicorn.HookManager.RemoveGetMessageHookHandler(GetMessageProcHook); 
    } 
    return res; 
} 

如果您遇到任何其他問題，讓我知道。

Answer 3

感謝MD.Unicorn。 PeekMessage和RemoveAllKeyMessages方法運行良好，除了一個小的改變。

我一直在做這個問題的更多的研究，顯然這是一個已知的問題（甚至在微軟連接列爲一個不會修復問題），MessageBox接受KeyDown事件的輸入選項，然後關閉窗口，那麼返回的窗口將在稍後收到KeyUp事件。

當我知道這KeyUp事件不會立即出現在將來的某個時候，但。 （本身的RemoveAllKeyMessages沒有解決這個問題。）我只是調整輪詢它的方法如下。我已將該方法重命名爲指示它是MessageBox問題的自定義用法。

public static void RemoveMessageBoxKeyMessages() 
    { 
     //Loop until the MessageBox KeyUp event fires 
     var timeOut = DateTime.Now; 
     while (PeekKeyMessage(false) == null && DateTime.Now.Subtract(timeOut).TotalSeconds < 1) 
      System.Threading.Thread.Sleep(100); 

     while (PeekKeyMessage(true) != null) ; // Empty body. Every call to the method removes one key message. 
    } 

除非有一個明顯的缺陷（比如果消息框不發送KeyUp事件等），這應該是一種具有類似問題的其他解決方案。