c++ Win32 Api 线程内的 GetMessage 关闭程序

Question

我正在使用 win32 api 构建一个界面，我想在另一个 class 中用一个线程来管理所有的东西，以继续在 main 中工作。我有这个代码：

WindowManager.h

class UIManager::WindowManager {
private:
    //Class data
    HINSTANCE hInstance;
    WNDCLASSEX winClass; /* Data structure for the windowclass */
    MSG msg;
    HWND hwnd;
    //Window Data
    LPCSTR wiName;
    int startX = 250;
    int startY = 150;
    int endX = 544;
    int endY = 375;
    //Private managers
    void makeWindow();
public:
    WindowManager(HINSTANCE & hInstance, std::string wiName = "Window Name");
    void show();
};

WindowManager.c（我使用 bind 是因为我在命名空间中有 class，这是我发现线程允许我编译的唯一方法而不是抛出错误）

#include "WindowManager.h"

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

//Private
//
void UIManager::WindowManager::makeWindow()
{
    int ms = GetMessage(&msg, 0, 0, 0); //I do this to see if it gets to
    while (GetMessage(&msg, NULL, 0, 0)) { //this part, but never happens
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
}

//Public
//
UIManager::WindowManager::WindowManager(HINSTANCE & hInstance, std::string wiName)
{
    this->wiName = wiName.c_str();
    this->hInstance = hInstance;
    winClass.cbSize = sizeof(winClass);
    winClass.hInstance = hInstance;
    winClass.lpszClassName = this->wiName;
    winClass.lpfnWndProc = WndProc; //Execution callback
    //Load default editable ellements
    winClass.hCursor = LoadCursor(0, IDC_ARROW);        /*Default*/
    winClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);   /*Default*/     //Alt+Tab Dialog
    winClass.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
    winClass.lpszMenuName = NULL;                       /* No menu */
    RegisterClassEx(&winClass);

    //Create Window
    hwnd = CreateWindowEx(
        0,
        this->wiName,           /* Title Class */
        this->wiName,           /* Title Text */
        WS_OVERLAPPED | WS_MINIMIZEBOX | WS_SYSMENU | WS_VISIBLE | WS_OVERLAPPEDWINDOW,
        startX,                         /* X Start */
        startY,                         /* Y Start */
        endX,                           /* The programs width */
        endY,                           /* and height in pixels */
        HWND_DESKTOP,                   /* The window is a child-window to desktop */
        NULL,                           /* No menu */
        hInstance,              /* Program Instance handler */
        NULL
    );
    SetWindowPos(hwnd, 0, 0, 0, 20, 20, 0);
}

void UIManager::WindowManager::show()
{
    std::thread listener(std::bind(&WindowManager::makeWindow, this));
    listener.detach();
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_CREATE:
    { //This part is executed
        //...blablabla
        break;
    }

    case WM_COMMAND:
    {//This part is never executed
        //...blablabla
        break;
    }

    case WM_DESTROY:
    {//This part is never executed
        //...blabla
        PostQuitMessage(0);
        break;
    }
    }
    return DefWindowProc(hwnd, msg, wParam, lParam);
}

window 执行和显示正确，甚至执行 WM_CREATE，但是当 "GetMessage" 执行时它立即结束程序而没有抛出任何错误或类似的东西。

我用 GetMessage 的值添加了一个 int 以查看它是否在调试模式下到达 "while" 但它确实发生了。有没有办法查看可能抛出的错误或阻止它关闭程序？还是我在线程内部调用 "GetMessage" 时做错了？

Answer 1

您的代码有几个问题：

您在一个线程中创建 window，但尝试在另一个线程中运行消息循环。 GetMessage 仅处理属于调用线程的 windows 的消息。
您永远不会等待后台线程处理消息，而是与其分离并继续在可能结束应用程序的主线程中执行。
您不检查 GetMessage 返回的值并将其用作布尔值。

如果您想创建后台 ui 线程，您需要将所有 window 创建代码移到那里并在线程上调用 join。消息循环应该是这样的：

::MSG msg;
for(;;)
{
    auto const res{::GetMessage(&msg, NULL, 0, 0))};
    if(0 < res)
    {
        ::TranslateMessage(&msg);
        ::DispatchMessage(&msg);
    }
    else if(0 == res)
    {   //  PostQuitMessage was called...
        break;
    }
    else
    {   //  an error occurred...
        break;
    }
}

c++ Win32 Api 线程内的 GetMessage 关闭程序

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getmessage