Thread: No data showing in combo box

I'm adding a combo box to a dialog box in the resource editor of Visual Studio and am running into problems. The combo box is a drop list, and I'm adding data to the list via the properties menu. If I test the box while still in the resource editor (Ctrl-T) it works perfectly fine, I can see all of the items in the list and select them at will. But when I run a program that calls the dialog box, the list is suddenly empty. Heres the simple test program I've made to run the dialog box. Its just a blank window with one menu option with the ID of ID_TEST_TEST that calls the dialog box which contains the combo box and an OK button:

Code:

#include<windows.h>
#include "resource.h"
using namespace std;



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

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int iCmdShow)
{
	HMENU hMenu;
	static TCHAR szAppName[]=TEXT("Assessment Runner");
	HWND hwnd;   // handle to a window
	MSG msg;   // message
	WNDCLASS wndclass;  // window class we are declaring


	// Now we set the attributes for our window
	wndclass.style=CS_HREDRAW | CS_VREDRAW;  // Style, in this case can be redrawn
	wndclass.lpfnWndProc=WndProc;  // window process name - handles message calls
	wndclass.cbClsExtra=0;  // Extra space for the window
	wndclass.cbWndExtra=0;  // ditto
	wndclass.hInstance=hInstance;  // program instance name passed to WinMain
	wndclass.hIcon=LoadIcon(NULL, IDI_APPLICATION);  // Load icon for the tray
	wndclass.hCursor=LoadCursor(NULL, IDC_ARROW);  // Load icon for the mouse arrow
	wndclass.hbrBackground=(HBRUSH) GetStockObject(WHITE_BRUSH);  // Load background color
	wndclass.lpszMenuName=NULL;  // Set menu - none here
	wndclass.lpszClassName=szAppName;  // Sets window name, taken from above

	hMenu=LoadMenu(hInstance,MAKEINTRESOURCE(IDR_MENU1));

	if (!RegisterClass(&wndclass))
	{
		MessageBox(NULL, TEXT("Error running program!"), szAppName, MB_ICONERROR);
		return 0;
	}



	hwnd=CreateWindow(szAppName, TEXT("Assessment Runer"), WS_OVERLAPPEDWINDOW,
		CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, hMenu,
		hInstance, NULL);  // Create the window!  Name, Title, Style, x Position, y Position
	                       // X size, Y size, parent window handle, window menu handle, 
						   // program instance handle, creation parameters(passing variables)


	ShowWindow(hwnd, iCmdShow);  // now show the window
	UpdateWindow(hwnd);   // update it

	while (GetMessage(&msg, NULL, 0, 0))  // gets message from mouse and keyboard, always non
		                                  // zero until you quit the window
	{
		TranslateMessage(&msg);           // translates message from message queue (mouse/keyboard/etc)
		DispatchMessage(&msg);			  // sends to WndProc to translate and tell what to do!
	}

	return msg.wParam;

}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static HINSTANCE hInstance;

	switch (message)
	{
	case WM_CREATE:
		hInstance=((LPCREATESTRUCT) lParam)->hInstance;
		return 0;

	case WM_COMMAND:
		switch (LOWORD(wParam))
		{
		case ID_TEST_TEST:
			DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), hwnd, MainDialogProc);
			break;
		}

		return 0;

	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}

	return DefWindowProc(hwnd, message, wParam, lParam);
}

BOOL CALLBACK MainDialogProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{

	switch (message)
	{
	case WM_INITDIALOG:
		return TRUE;

	case WM_COMMAND:
		switch (LOWORD (wParam))
		{
		case IDOK:  // user clicked OK button, return
			EndDialog(hDlg, TRUE);
			return TRUE;
		}
		break;
	}

	return FALSE;
}

If you look at your resource script, you'll see that the combo box data is stored in a "DLGINIT" resource. This is used internally by CDialog to perform certain dialog initializations on WM_INITDIALOG.

CDialog is MFC, so you have to use MFC to make it work. Otherwise, add the data manually on WM_INITDIALOG.

gg

Ok thanks, good to know. Its been over a year since I've done Windows programming and it feels like I've forgotten everything. I can't test this til tomorrow unfortunately but to add data manually do I use the SendMessage function? For example:

Code:

SendMessage(hwndCombo, LB_ADDSTRING , 0 , TEXT("Test data"));

If this is correct, how do I get the handle for a combo box that is created using the resource editor as opposed to CreateWindow? If the ID for the combo box is ID_COMBO1 and the handle to the dialog box is hDlg I'm guessing:

Code:

hwndCombo=GetDlgItem(hDlg, IDC_COMBO1);

Is this correct?

Yes and yes, except use CB_ADDSTRING it it's really a combo box.

gg

Thanks, you da man