在對(duì)話框程序中，我們經(jīng)常是利用對(duì)話框上的子控件進(jìn)行命令響應(yīng)來(lái)處理一些事件。如果我們想要讓對(duì)話框（子控件的父窗口）類(lèi)來(lái)響應(yīng)我們的按鍵消息，我們可以通過(guò)ClassWizard對(duì)WM_KEYDOWN消息進(jìn)行響應(yīng)，當(dāng)程序運(yùn)行后，我們按下鍵盤(pán)上的按鍵，但對(duì)話框不會(huì)有任何的反應(yīng)。這是因?yàn)樵趯?duì)話框程序中，某些特定的消息，例如按鍵消息，它們被Windows內(nèi)部的對(duì)話框過(guò)程處理了（即在基類(lèi)中完成了處理，有興趣的讀者可以查看MFC的源代碼），或者被發(fā)送給子控件進(jìn)行處理，所以我們?cè)趯?duì)話框類(lèi)中就捕獲不到按鍵的消息了。
既然我們知道了這個(gè)處理的過(guò)程，我們就可以找到底層處理按鍵消息的函數(shù)，然后在子類(lèi)中重載它，就可以在對(duì)話框程序中處理按鍵消息了。在MFC中，是利用BOOL ProcessMessageFilter(int code, LPMSG lpMsg)這個(gè)虛函數(shù)來(lái)過(guò)濾或響應(yīng)菜單和對(duì)話框的特定Windows消息。下面我們通過(guò)程序給大家演示基于對(duì)話框的應(yīng)用程序?qū)M_KEYDOWN消息的捕獲。
第一步：新建一個(gè)工程，選擇MFC AppWizard (exe)，工程名為WinSun，點(diǎn)擊ok，進(jìn)入下一步，選擇Dialog based，點(diǎn)擊Finish。
第二步：在CWinSunApp類(lèi)上點(diǎn)擊右鍵，選擇Add Member Varialbe，增加一個(gè)類(lèi)型為HWND，變量名m_hwndDlg的public的變量。
代碼如下：
class CWinSunApp : public CWinApp
{
public:
HWND m_hwndDlg;
CWinSunApp();
// Overrides
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CWinSunApp)
public:
virtual BOOL InitInstance();
//}}AFX_VIRTUAL
// Implementation
//{{AFX_MSG(CWinSunApp)
// NOTE - the ClassWizard will add and remove member functions here.
// DO NOT EDIT what you see in these blocks of generated code !
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
BOOL CWinSunApp::InitInstance()
{
AfxEnableControlContainer();
// Standard initialization
// If you are not using these features and wish to reduce the size
// of your final executable, you should remove from the following
// the specific initialization routines you do not need.
#ifdef _AFXDLL
Enable3dControls(); // Call this when using MFC in a shared DLL
#else
Enable3dControlsStatic(); // Call this when linking to MFC statically
#endif
CWinSunDlg dlg;
m_pMainWnd = &dlg;
int nResponse = dlg.DoModal();
if (nResponse == IDOK)
{
// TODO: Place code here to handle when the dialog is
// dismissed with OK
}
else if (nResponse == IDCANCEL)
{
// TODO: Place code here to handle when the dialog is
// dismissed with Cancel
}
// Since the dialog has been closed, return FALSE so that we exit the
// application, rather than start the application's message pump.
m_hwndDlg=NULL;
return FALSE;
}
BOOL CWinSunApp::ProcessMessageFilter(int code, LPMSG lpMsg)
{
// TODO: Add your specialized code here and/or call the base class
if(m_hwndDlg!=NULL)
{
//判斷消息，如果消息是從對(duì)話框發(fā)出的或者其子控件發(fā)出的，我們就進(jìn)行處理。sunxin
if((lpMsg->hwnd==m_hwndDlg) || ::IsChild(m_hwndDlg,lpMsg->hwnd))
{
//如果消息是WM_KEYDOWN，我們就彈出一個(gè)消息框。sunxin
if(lpMsg->message==WM_KEYDOWN)
{
AfxMessageBox("捕獲WM_KEYDOWN消息成功！");
}
}
}
return CWinApp::ProcessMessageFilter(code, lpMsg);
}
BOOL CWinSunDlg::OnInitDialog()
{
CDialog::OnInitDialog();
// Add "About..." menu item to system menu.
// IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000);
CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
}
// Set the icon for this dialog. The framework does this automatically
// when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon
// TODO: Add extra initialization here
//將對(duì)話框的句柄傳遞到CWinSunApp類(lèi)中。sunxin
((CWinSunApp*)AfxGetApp())->m_hwndDlg=m_hWnd;
return TRUE; // return TRUE unless you set the focus to a control
}
void CWinSunDlg::OnDestroy()
{
CDialog::OnDestroy();
// TODO: Add your message handler code here
((CWinSunApp*)AfxGetApp())->m_hwndDlg=NULL;
}
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