MessageBoxTimeout API

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引言

出于未知的原因，微软从未公开文档化位于 user32.dll 中的 MessageBoxTimeout API。因此，这里提供给那些需要一个超时并自动关闭的消息框（如果用户未先响应）的人们。

使用代码

该代码可用于 UNICODE 和 MBCS，只需将以下代码添加到源文件（cpp）中即可

#include <windows.h>
#include <tchar.h>

//Functions & other definitions required-->
typedef int (__stdcall *MSGBOXAAPI)(IN HWND hWnd, 
        IN LPCSTR lpText, IN LPCSTR lpCaption, 
        IN UINT uType, IN WORD wLanguageId, IN DWORD dwMilliseconds);
typedef int (__stdcall *MSGBOXWAPI)(IN HWND hWnd, 
        IN LPCWSTR lpText, IN LPCWSTR lpCaption, 
        IN UINT uType, IN WORD wLanguageId, IN DWORD dwMilliseconds);

int MessageBoxTimeoutA(IN HWND hWnd, IN LPCSTR lpText, 
    IN LPCSTR lpCaption, IN UINT uType, 
    IN WORD wLanguageId, IN DWORD dwMilliseconds);
int MessageBoxTimeoutW(IN HWND hWnd, IN LPCWSTR lpText, 
    IN LPCWSTR lpCaption, IN UINT uType, 
    IN WORD wLanguageId, IN DWORD dwMilliseconds);

#ifdef UNICODE
    #define MessageBoxTimeout MessageBoxTimeoutW
#else
    #define MessageBoxTimeout MessageBoxTimeoutA
#endif 

#define MB_TIMEDOUT 32000

int MessageBoxTimeoutA(HWND hWnd, LPCSTR lpText, 
    LPCSTR lpCaption, UINT uType, WORD wLanguageId, 
    DWORD dwMilliseconds)
{
    static MSGBOXAAPI MsgBoxTOA = NULL;

    if (!MsgBoxTOA)
    {
        HMODULE hUser32 = GetModuleHandle(_T("user32.dll"));
        if (hUser32)
        {
            MsgBoxTOA = (MSGBOXAAPI)GetProcAddress(hUser32, 
                                      "MessageBoxTimeoutA");
            //fall through to 'if (MsgBoxTOA)...'
        }
        else
        {
            //stuff happened, add code to handle it here 
            //(possibly just call MessageBox())
            return 0;
        }
    }

    if (MsgBoxTOA)
    {
        return MsgBoxTOA(hWnd, lpText, lpCaption, 
              uType, wLanguageId, dwMilliseconds);
    }

    return 0;
}

int MessageBoxTimeoutW(HWND hWnd, LPCWSTR lpText, 
    LPCWSTR lpCaption, UINT uType, WORD wLanguageId, DWORD dwMilliseconds)
{
    static MSGBOXWAPI MsgBoxTOW = NULL;

    if (!MsgBoxTOW)
    {
        HMODULE hUser32 = GetModuleHandle(_T("user32.dll"));
        if (hUser32)
        {
            MsgBoxTOW = (MSGBOXWAPI)GetProcAddress(hUser32, 
                                      "MessageBoxTimeoutW");
            //fall through to 'if (MsgBoxTOW)...'
        }
        else
        {
            //stuff happened, add code to handle it here 
            //(possibly just call MessageBox())
            return 0;
        }
    }

    if (MsgBoxTOW)
    {
        return MsgBoxTOW(hWnd, lpText, lpCaption, 
               uType, wLanguageId, dwMilliseconds);
    }

    return 0;
}
//End required definitions <--

按如下方式调用该函数

//you must load user32.dll before calling the function
HMODULE hUser32 = LoadLibrary(_T("user32.dll"));
    
if (hUser32)
{
    int iRet = 0;
    UINT uiFlags = MB_OK|MB_SETFOREGROUND|MB_SYSTEMMODAL|MB_ICONINFORMATION;
    
    iRet = MessageBoxTimeout(NULL, _T("Test a timeout of 2 seconds."), 
                      _T("MessageBoxTimeout Test"), uiFlags, 0, 2000);
    //iRet will = 1

    uiFlags = MB_YESNO|MB_SETFOREGROUND|MB_SYSTEMMODAL|MB_ICONINFORMATION;

    iRet = MessageBoxTimeout(NULL, _T("Test a timeout of 5 seconds."), 
                      _T("MessageBoxTimeout Test"), uiFlags, 0, 5000);
    //iRet will = MB_TIMEDOUT if no buttons pressed, button values otherwise
        
    //only unload user32.dll when you have no further need 
    //for the MessageBoxTimeout function
    FreeLibrary(hUser32);
}

该函数将返回一个整数值，要么是 MB_TIMEDOUT 值，表示达到超时时间并且消息框自动关闭，要么是用户点击的按钮所代表的值。请注意，当使用仅带有“确定”按钮的消息框（MB_OK 标志）时，返回值始终为 1。

提供的示例代码适用于 Visual Studio .NET 2003，但可以轻松地在其他编译器中使用。

关注点

你可能会想知道，是否有保证微软不会有一天删除此函数。坦白地说，没有，但是有趣的是，内部所有文档化的 MessageBox* 函数都调用 MessageBoxTimeout API，并简单地将 0xFFFFFFFF 作为超时时间传递（非常长的时间），因此被删除的可能性很小。