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VC程序中定制对话框中的回车键

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基于对话框的程序中，每当用户按下回车键时，程序都会退出，其效果和按下对话框中的默认\"OK\"按钮是一样的。

作者：刘涛来源：天极开发 2007年10月16日

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　三、程序代码

/////////////////////////////////////////
#include "stdafx.h"
// Generic dialog-that-uses-accelerators.
class CDlgWithAccelerators : public CDialog {
public:
　CDlgWithAccelerators(UINT nIDTemplate, CWnd* pParentWnd = NULL);
　CDlgWithAccelerators(LPCTSTR lpszTemplateName, CWnd* pParentWnd = NULL);
　~CDlgWithAccelerators();
protected:
　HACCEL m_hAccel; // accelerator table
　// MFC overrides
　virtual BOOL OnInitDialog();
　virtual BOOL PreTranslateMessage(MSG* pMsg);
　DECLARE_MESSAGE_MAP()
};

///////////////////////////////////////////
// CDlgWithAccelerators is a general-purpose class that adds accelerators to CDialog.
#include "stdafx.h"
#include "dlgaccel.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
BEGIN_MESSAGE_MAP(CDlgWithAccelerators,CDialog)
END_MESSAGE_MAP()
CDlgWithAccelerators::CDlgWithAccelerators(LPCTSTR lpszTemplateName,
CWnd* pParentWnd) : CDialog(lpszTemplateName, pParentWnd)
{}

CDlgWithAccelerators::CDlgWithAccelerators(UINT nIDTemplate,
CWnd* pParentWnd) : CDialog(nIDTemplate, pParentWnd)
{}

CDlgWithAccelerators::~CDlgWithAccelerators()
{}

/////////////////////////// Pre-translate message: translate keystrokes using acclerator table.
BOOL CDlgWithAccelerators::PreTranslateMessage(MSG* pMsg)
{
　if (WM_KEYFIRST <= pMsg->message && pMsg->message <= WM_KEYLAST) {
　　HACCEL hAccel = m_hAccel;
　　if (hAccel && ::TranslateAccelerator(m_hWnd, hAccel, pMsg))
　　　return TRUE;
　}
　return CDialog::PreTranslateMessage(pMsg);
}

//////////////////// Initialize dialog: load accelerators
BOOL CDlgWithAccelerators::OnInitDialog()
{
　BOOL bRet = CDialog::OnInitDialog();
　// Load dialog's accelerators
　m_hAccel = ::LoadAccelerators(AfxGetResourceHandle(),
　m_lpszTemplateName); // use same resource name as dialog
　return bRet;
}

/////////////////////////////////////////////////////////////////////////
#include "stdafx.h"
#include "resource.h"
#include "dlgaccel.h"
#include "TraceWin.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////MFC app
class CMyApp : public CWinApp {
public:
　CMyApp();
　~CMyApp();
　virtual BOOL InitInstance();
　DECLARE_MESSAGE_MAP()
};

CMyApp theApp; // THE one-and-only app

//////////// frame window
class CMainFrame : public CFrameWnd {
protected:
　virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
public:
　CMainFrame();
　~CMainFrame();
};

//////////////////// Typical dialog
class CMyDlg : public CDlgWithAccelerators {
public:
　CMyDlg(CWnd* pParent = NULL); // standard constructor
protected:
　HICON m_hIcon;
　void NextInTabOrder();
　// MFC overrides
　virtual BOOL OnInitDialog();
　afx_msg void OnMyEnter();
　afx_msg LRESULT OnGetDefID(WPARAM wp, LPARAM lp);
　DECLARE_MESSAGE_MAP()
};

BEGIN_MESSAGE_MAP(CMyApp, CWinApp)
END_MESSAGE_MAP()

CMyApp::CMyApp()
{
　// nothing to do
}

CMyApp::~CMyApp()
{
　// nothing to do
}

//////////////////// InitInstance: create dialog as child
BOOL CMyApp::InitInstance()
{
　// create frame window and load it
　CMainFrame* pFrame = new CMainFrame;
　m_pMainWnd = pFrame;
　pFrame->LoadFrame(IDR_MAINFRAME, WS_OVERLAPPED, NULL, NULL);
　CMyDlg dlg(pFrame); // create dialog and run it
　int nResponse = dlg.DoModal();
　if (nResponse == IDOK)
　{}
　else if (nResponse == IDCANCEL)
　{}
　return FALSE; // quit
}

CMainFrame::CMainFrame()
{
　// nothing to do
}

CMainFrame::~CMainFrame()
{
　// nothing to do
}

///////////// Pre-create window: set WS_EX_TOOLWINDOW style to hide dialog from task bar
BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)
{
　if (CFrameWnd::PreCreateWindow(cs)) {
　　cs.dwExStyle |= WS_EX_TOOLWINDOW;
　　return TRUE;
　}
　return FALSE;
}

BEGIN_MESSAGE_MAP(CMyDlg, CDlgWithAccelerators)
ON_COMMAND(ID_MY_ENTER, OnMyEnter)

// The following is NOT needed since I am using accelerators to map
// ENTER to ID_MY_ENTER. But if all you want to do is ignore the Enter key,
// you can handle DM_GETDEFID as below.
// ON_MESSAGE(DM_GETDEFID, OnGetDefID) // not used
END_MESSAGE_MAP()

CMyDlg::CMyDlg(CWnd* pParent) : CDlgWithAccelerators(IDD_MYDIALOG, pParent)
{}

//////////////////// Initialize dialog:
BOOL CMyDlg::OnInitDialog()
{
　CDlgWithAccelerators::OnInitDialog();
　// Set the icon for this dialog. The framework does this automatically
　// when the application's main window is not a dialog
　m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
　ASSERT(m_hIcon);
　SetIcon(m_hIcon, TRUE); // Set big icon
　SetIcon(m_hIcon, FALSE); // Set small icon
　// use same resource name as dialog to load dialog's accelerators
　m_hAccel = ::LoadAccelerators(AfxGetResourceHandle(),m_lpszTemplateName);
　ASSERT(m_hAccel);
　return TRUE; // return TRUE unless you set the focus to a control
}

//////////////////// This is called to handle ID_MY_ENTER--ie, Enter key.
void CMyDlg::OnMyEnter()
{
　TRACE(_T("CMyDlg::OnMyEnter\n"));
　NextInTabOrder(); // move to next control
}

//////////////////// Helper function to move focus to the next control.
void CMyDlg::NextInTabOrder()
{
　CWnd* pWndNext = GetNextDlgTabItem(GetFocus());
　if (pWndNext) {
　　pWndNext->SetFocus();
　}
}

//////////////////
// This function is not used, since its message map entry is commented out.
// If all you want to do is ignore the Enter key (not map it to a command),
// then all you have to do is return zero here. Note that you MUST return
// the special code DC_HASDEFID in the high-order word!!
LRESULT CMyDlg::OnGetDefID(WPARAM wp, LPARAM lp)
{
　TRACE(_T("CMyDlg::OnGetDefID\n"));
　return MAKELONG(0,DC_HASDEFID);
}

　　四、小结

　　综上所述，MFC中为对话框添加加速键功能的方法就是：加载加速键和重载PreTranslateMessage（）函数。也就是说，如果开发人员决定在对话框中使用加速键，不用去操心OnGetDefID（）函数的处理，而是要重点实现加速键对应的WM_COMMAND消息响应处理函数。

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