如何禁用CComboBox mfc键盘导航？

Question

How i can disable CComboBox mfc keyboard navigation, i need when i press key on keyboard with open dropdown list, item must not selecting. Thanks!

Answer 1

A simple solution without subclassing the combobox is to set its first child window (which is the CEdit box) to readonly, like this :

GetDlgItem(IDC_MY_COMBO)->GetWindow(GW_CHILD)->SendMessage(EM_SETREADONLY, 1, 0);

Answer 2

If you really just mean: "how do I disable the control from being changed?", then just call the EnableWindow method on the CComboBox.

But if you really mean you just want to block keyboard messages from hitting the control, then use window subclassing to swallow keyboard messages. (Don't confuse the term "window subclassing" with C++ classes - not the same thing). Basically, we're just going to intercept all WM_CHAR and WM_KEYDOWN messages associated with the combo box and let all the other messages pass.

Do this:

WNDPROC g_prevFunc = NULL;

LRESULT MyWindowHook(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    if ((uMsg == WM_CHAR) || (uMsg == WM_KEYDOWN) || (uMsg == WM_KEYUP))
    {
        return 0; // swallow message
    }

    return ::CallWindowProcW(g_prevFunc, hWnd, uMsg, wParam, lParam);
}


void MySubclassWindow(HWND hwnd)
{
    g_prevFunc = (WNDPROC)::SetWindowLongW(hwnd, GWL_WNDPROC, (LONG_PTR)MyWindowHook);
}

// wherever your code gets initialized
CYourWindow::OnInit()
{
   // whatever other initialization you got going on...

  // I'm assuming your CComboBox is named something like m_combobox.

  ::MySubclassWindow(m_combobox.m_hWnd);

}

Double check to make sure this doesn't break tab key navigation. I just tried and it seems to work fine. You may not need to swallow WM_CHAR, just might need to swallow WM_KEYUP and WM_KEYDOWN. Some experimentation on your part is likely needed.

There's also an MFC method on the CWnd class called SubclassWindow. So if you want to go pure MFC, you can look into this as well.