[英]C++ Win32 API Combo Box freezes when opened
我正在嘗試使用下拉組合框( CBS_DROPDOWN
或CBS_DROPDOWNLIST
)來工作。 問題是,每當我打開組合框時,整個窗口都會“凍結”(它什么也沒有響應,甚至無法關閉,它會忽略點擊)。 “解凍”的唯一方法是按“ esc”鍵。
當窗口“凍結”時,組合框不會收到任何消息,也不會移動鼠標,單擊等。
這是我用來創建組合框的代碼:
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()”函數僅向組合框添加一些字符串並設置初始元素:
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,簡單的( CBS_SIMPLE
)組合框可以工作。
這是完整的代碼:
#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;
}
while (GetMessage(&msg, hwnd, 0, 0) > 0)
僅泵送主窗口消息。 您需要為線程中的所有窗口提供排隊的消息。 將此行更改為
while (GetMessage(&msg, NULL, 0, 0))
如GetMessage
文檔中所述,為第二個參數傳遞NULL
將為線程擁有的所有窗口檢索消息。
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