當GetForegroundWindow（）發生更改時，是否有任何系統事件觸發？

Question

我開發一個需要得到在應用程序運行時，我目前正在執行一個呼叫到GetForegroundwindow（）每隔半秒一直處於活動狀態的窗口名的應用程序，但是這很難準確，我不想把它設置爲100ms的時間間隔，我認爲這很糟糕，不準確，是否有任何系統事件可以爲我做到這一點？

謝謝。

Answer 1

- 更新 -

你可以使用SetWindowsHookEx監視當前桌面，但這並不在託管代碼工作。相反，您必須使用SetWinEventHook。

你問如何使用SetWinEventHook P/Invoke方法。這裏是你的答案：

首先確保這條線是在你的代碼文件的頂部：

Imports System.Runtime.InteropServices 

接下來，聲明所有你需要調用電話：

Public Const WINEVENT_OUTOFCONTEXT = &H0 
'' Events are ASYNC 

Public Const WINEVENT_SKIPOWNTHREAD = &H1 
'' Don't call back for events on installer's thread 

Public Const WINEVENT_SKIPOWNPROCESS = &H2 
'' Don't call back for events on installer's process 

Public Const WINEVENT_INCONTEXT = &H4 
'' Events are SYNC, this causes your dll to be injected into every process 

    Public Declare Function SetWinEventHook Lib "user32.dll" _ 
     (eventMin As UInteger, _ 
     eventMax As UInteger, _ 
     hmodWinEventProc As IntPtr, _ 
     lpfnWinEventProc As IntPtr, _ 
     idProcess As UInteger, _ 
     idThread As UInteger, _ 
     dwflags As UInteger) As IntPtr 

    Public Declare Function UnhookWinEvent Lib "user32.dll" _ 
     (hWinEventHook As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean 

    Public Delegate Sub WinEventProc(_ 
      hWinEventHook As IntPtr, _ 
      [event] As UInteger, _ 
      hwnd As IntPtr, _ 
      idObject As Integer, _ 
      idChild As Integer, _ 
      dwEventThread As UInteger, _ 
      dwmsEventTime As UInteger) 

下一頁，你聲明一個函數和一個新變量作爲函數的地址函數：

Public Sub EventCallBack(_ 
     hWinEventHook As IntPtr, _ 
     [event] As UInteger, _ 
     hwnd As IntPtr, _ 
     idObject As Integer, _ 
     idChild As Integer, _ 
     dwEventThread As UInteger, _ 
     dwmsEventTime As UInteger) 

' Some code goes here 
    End Sub 

    Private eventProc As New WinEventProc(AddressOf EventCallBack) 
    Private hEventHook As IntPtr 

Fin盟友，你將其結合在一起，和你通過下面的代碼行創建你的鉤子（0和255爲任意數字，你想要觀看的最小和最大消息代碼替換它們）：

hEventHook = SetWinEventHook(0, _ 
          255, _ 
          IntPtr.Zero, _ 
          Marshal.GetFunctionPointerForDelegate(eventProc), _ 
          0, _ 
          0, _ 
          WINEVENT_OUTOFCONTEXT) 

當你的程序已經完成了以下行添加到應用程序終止事件，或窗體的Dispose或無法最終確定方法：

 UnhookWinEvent(hEventHook) 

而這個運行在我的測試應用程序如預期。