C++ Win32 API组合框在打开时冻结

Question

我正试图让一个下拉组合框(CBS_DROPDOWN或CBS_DROPDOWNLIST)工作.问题是,无论何时打开组合框,整个窗口都"冻结"(它不响应任何东西,甚至不能关闭它,它会忽略点击)."解冻"的唯一方法是按"esc"键.

当窗口被"冻结"时,组合框不会收到任何消息,也不会移动鼠标,点击等.

这是我用来创建组合框的代码:

case WM_CREATE:
    hComboBox = CreateWindow("COMBOBOX", nullptr,
        WS_CHILD | WS_VISIBLE | WS_OVERLAPPED | CBS_DROPDOWNLIST,
        25, 25, 150, 280, hwnd, (HMENU)12345, GetModuleHandle(nullptr), nullptr);
    populate_cb();
    break;

"populate_cb()"函数只是在组合框中添加了一些字符串并设置了一个初始元素:

void populate_cb() {
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 1");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 2");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 3");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 4");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 5");
    SendMessage(hComboBox, CB_SETCURSEL, (WPARAM)2, 0);
}

但是,simple(CBS_SIMPLE)组合框可以工作.

这是完整的代码:

#include <Windows.h>

HWND hComboBox;

void populate_cb() {
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 1");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 2");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 3");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 4");
    SendMessage(hComboBox, CB_ADDSTRING, 0, (LPARAM)"Item 5");
    SendMessage(hComboBox, CB_SETCURSEL, (WPARAM)2, 0);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch (msg) {
    case WM_CREATE:
        hComboBox = CreateWindow("COMBOBOX", nullptr,
            WS_OVERLAPPED | WS_CHILD | WS_VISIBLE | CBS_DROPDOWNLIST,
            25, 25, 150, 280, hwnd, (HMENU)12345, GetModuleHandle(nullptr), nullptr);
        populate_cb();
        break;
    case WM_CLOSE:
        DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    WNDCLASSEX wcex;
    wcex.cbClsExtra = 0;
    wcex.cbSize = sizeof(WNDCLASSEX);
    wcex.cbWndExtra = 0;
    wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW);
    wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
    wcex.hIcon = LoadIcon(nullptr, IDI_APPLICATION);
    wcex.hIconSm = LoadIcon(nullptr, IDI_APPLICATION);
    wcex.hInstance = hInstance;
    wcex.lpfnWndProc = WndProc;
    wcex.lpszClassName = "WindowClass";
    wcex.lpszMenuName = nullptr;
    wcex.style = 0;

    if (!RegisterClassEx(&wcex)) {
        MessageBox(nullptr, "Window class registration failed!", "Error", MB_OK | MB_ICONERROR);
        return 1;
    }

    HWND hwnd = CreateWindowEx(WS_EX_CLIENTEDGE, "WindowClass", "Window Title",
        WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 640, 480, nullptr,
        nullptr, hInstance, nullptr);

    if (!hwnd) {
        MessageBox(nullptr, "Window creation failed!", "Error", MB_OK | MB_ICONERROR);
        return 1;
    }

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    MSG msg;
    while (GetMessage(&msg, hwnd, 0, 0) > 0) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return msg.wParam;
}

Answer 1

while (GetMessage(&msg, hwnd, 0, 0) > 0) 

仅为主窗口泵送消息.您需要为线程中的所有窗口提供排队消息服务.将此行更改为

while (GetMessage(&msg, NULL, 0, 0)) 

正如在第二个参数的GetMessage传递文档中所解释的那样,NULL检索线程拥有的所有窗口的消息.