为何VBA调用SetForegroundWindow无法将Excel置于前台获取焦点？

问题根源 #

Windows系统对SetForegroundWindow有焦点保护机制：只有当前台窗口所属进程主动放弃焦点，或者你的进程通过用户交互获得激活权限时，调用该API才能成功。你启动Chrome后，Chrome成为前台进程，Excel进程此时没有激活权限，直接调用SetForegroundWindow会被系统拦截，返回值0就是明证。

可行解决方案 #

方案1：模拟用户交互触发激活 #

通过发送Alt键的消息，让系统认为用户主动操作了Excel，从而获得激活权限。需要新增keybd_eventAPI：

Private Declare PtrSafe Function SetForegroundWindow Lib "user32" (ByVal HWnd As LongPtr) As Long
Private Declare PtrSafe Sub keybd_event Lib "user32" (ByVal bVk As Byte, ByVal bScan As Byte, ByVal dwFlags As Long, ByVal dwExtraInfo As LongPtr)
Private Const VK_MENU As Byte = &H12 'Alt键的虚拟键码
Private Const KEYEVENTF_KEYUP As Long = &H2

Sub RestoreExcelFocus()
    ' 先发送Alt键按下再松开，触发系统的焦点判定
    keybd_event VK_MENU, 0, 0, 0
    keybd_event VK_MENU, 0, KEYEVENTF_KEYUP, 0
    
    ' 再调用SetForegroundWindow
    SetForegroundWindow Application.HWnd
End Sub

方案2：使用AttachThreadInput关联线程 #

通过将Excel的线程和当前前台窗口的线程关联，获得激活权限：

Private Declare PtrSafe Function SetForegroundWindow Lib "user32" (ByVal HWnd As LongPtr) As Long
Private Declare PtrSafe Function GetForegroundWindow Lib "user32" () As LongPtr
Private Declare PtrSafe Function GetWindowThreadProcessId Lib "user32" (ByVal HWnd As LongPtr, lpdwProcessId As Long) As Long
Private Declare PtrSafe Function AttachThreadInput Lib "user32" (ByVal idAttach As Long, ByVal idAttachTo As Long, ByVal fAttach As Long) As Long
Private Declare PtrSafe Function GetCurrentThreadId Lib "kernel32" () As Long

Sub RestoreExcelFocus()
    Dim foregroundHWnd As LongPtr
    Dim foregroundThreadId As Long
    Dim excelThreadId As Long
    
    foregroundHWnd = GetForegroundWindow()
    foregroundThreadId = GetWindowThreadProcessId(foregroundHWnd, 0)
    excelThreadId = GetCurrentThreadId()
    
    ' 关联线程
    AttachThreadInput foregroundThreadId, excelThreadId, 1
    ' 激活Excel窗口
    SetForegroundWindow Application.HWnd
    ' 解除关联
    AttachThreadInput foregroundThreadId, excelThreadId, 0
End Sub

为什么你的原有代码无效 #

你尝试的ShowWindow系列方法只能改变窗口的显示状态，无法突破系统的焦点保护机制。Sleep只是延迟执行，没有解决核心的权限问题，所以多次调用SetForegroundWindow依然失败。

内容的提问来源于stack exchange，提问作者k1dfr0std