Question

我有一个从Registering for Device Notification获取的代码示例，用于检测USB设备是否已被删除。此代码使用Win32 API，我已经成功构建并测试它。

当我尝试将此功能集成到QObject派生类中时，我在MessagePump()方法中遇到了崩溃：

void QObjectDerivedClass::MessagePump() {
    MSG message;
    int retVal;

    if (!m_hWnd) {
        return;
    }

    qDebug() << Q_FUNC_INFO;

    // Get all messages for any window that belongs to this thread,
    // without any filtering. Potential optimization could be
    // obtained via use of filter values if desired.

    while ((retVal = GetMessage(&message, m_hWnd,
                             MSG_FILTER_MIN, MSG_FILTER_MAX)) != 0) {
        if (retVal == -1) {
            break;
        } else {
            TranslateMessage(&message);
            DispatchMessage(&message);
        }
    }
}

您可以想象，我必须修改示例中的WndProc()回调，以便为此类使用静态成员并满足WNDCLASS对象，如下所示：

BOOL QObjectDerivedClass::InitWindowClass() {
    WNDCLASSEX wndClass;/* = {0};*/

    wndClass.cbSize = sizeof(WNDCLASSEX);
    wndClass.style = 0;
    wndClass.hInstance = reinterpret_cast<HINSTANCE>(GetModuleHandle(0));
    // WndProcThunk is an static member of QObjectDerivedClass
    wndClass.lpfnWndProc = reinterpret_cast<WNDPROC>(WndProcThunk);
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hIcon = NULL;
    wndClass.hIconSm = NULL;
    wndClass.hbrBackground = NULL;
    wndClass.hCursor = NULL;
    wndClass.lpszClassName = WND_CLASS_NAME;
    wndClass.lpszMenuName = NULL;

    if (!RegisterClassEx(&wndClass)) {
        qDebug() << Q_FUNC_INFO << "Unable to register window class. Error:"
             << QString::number(GetLastError());

        return FALSE;
    }

    m_instance = wndClass.hInstance;

    return TRUE;
}

应用程序崩溃时的调用堆栈是：

1                                                                0xd26128   
2  SetManipulationInputTarget             USER32                 0x7709d2b3 
3  DispatchMessageW                       USER32                 0x7707e88a 
4  DispatchMessageW                       USER32                 0x7707e4c0 
5  RealGetWindowClassW                    USER32                 0x7708a64f 
6  KiUserCallbackDispatcher               ntdll                  0x772e08c6 
7  QObjectDerivedClass::MessagePump       qobjectderived.cpp 165 0xa52e88   
8  QObjectDerivedClass::Start             qobjectderived.cpp 346 0xa52bc2   
9  wWinMain                               main.cpp           259 0xa525ff   
10 invoke_main                            exe_common.inl     118 0xa5516e   
11 __scrt_common_main_seh                 exe_common.inl     253 0xa54fd0   
12 __scrt_common_main                     exe_common.inl     296 0xa54e6d   
13 wWinMainCRTStartup                     exe_wwinmain.cpp   17  0xa55188   
14 BaseThreadInitThunk                    KERNEL32               0x73d862c4 
15 RtlSubscribeWnfStateChangeNotification ntdll                  0x772d0fd9 
16 RtlSubscribeWnfStateChangeNotification ntdll                  0x772d0fa4

知道如何解决这次崩溃吗？

编辑：发布标准输出：

int __stdcall wWinMain(struct HINSTANCE__ *,struct HINSTANCE__ *,wchar_t *,int)
int __stdcall QObjectDerivedClass::WndProcThunk(struct HWND__ *,unsigned int,unsigned int,long)
int __stdcall QObjectDerivedClass::WndProcThunk(struct HWND__ *,unsigned int,unsigned int,long)
int __stdcall QObjectDerivedClass::WndProcThunk(struct HWND__ *,unsigned int,unsigned int,long)
int __stdcall QObjectDerivedClass::WndProcThunk(struct HWND__ *,unsigned int,unsigned int,long)
void __thiscall QObjectDerivedClass::MessagePump(void)

Answer 1

你不需要重新实现任何本机消息：Qt已经为你做了。

相反，在具体QAbstractNativeEventFilter中重新实现nativeEventFilter时对Windows消息作出反应。重新实现也可以继承QObject - 确保QObject是第一个基类，因为这是继承QObject唯一受支持的方式。

要使用过滤器，请使用qApp->installNativeEventFilter安装。

Answer 2

WinApi本质上不支持C ++。 QT将抽象出将正确的消息传递到正确窗口所涉及的所有艰苦工作。您似乎试图绕过所有这些事情，并自己创建窗口和消息，这会导致您的问题。

为什么不跟随simple QT example并将更改插入其中，而不是重新发明轮子。

winapi - 从QObject派生类

2 个答案: