MFC控件数据交换:DDX

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     UpdateData(FALSE)-将变量的值显示到控件上

新建一个Win32 Application,选择A Simple Win32 Application,修改stdafx.h 中的windwos.h为afxwin.h,工程属性设置使用MFC静态库

编写如下测试代码

// DDX.cpp : Defines the entry point for the application.
//

#include "stdafx.h"
#include "resource.h"
class CMyDlg : public CDialog
{
public:
	CMyDlg ():CDialog(IDD_DIALOG1){}
	virtual void DoDataExchange (CDataExchange* pDX);
	virtual BOOL OnInitDialog ();
	virtual void OnOK();
protected:
	CButton m_wndOK;
	CString m_strEdit;
};
void CMyDlg::DoDataExchange (CDataExchange* pDX)
{
	//完成控件与变量的绑定
	DDX_Control (pDX, IDOK, m_wndOK);
	DDX_Text (pDX, IDC_EDIT1, m_strEdit);
}
BOOL CMyDlg::OnInitDialog ()
{
	if (!CDialog::OnInitDialog())
		return FALSE;
	// 初始化控件
	// 方式一：通过GetDlgItem操作控件
	CWnd *pWnd = GetDlgItem (IDCANCEL);
	pWnd->EnableWindow (FALSE);
	m_wndOK.MoveWindow (0, 0, 100, 100);
	m_wndOK.SetWindowText ("DDXOK");

	// 方式二：通过DDX操作控件
	m_strEdit = "Hello you";
	UpdateData (FALSE);
	return TRUE;
}
void CMyDlg::OnOK ()
{
	// 接收控件的值到关联的变量
	UpdateData (TRUE);
	AfxMessageBox (m_strEdit);
	CDialog::OnOK();
}
class CMyWinApp : public CWinApp
{
public:
	virtual BOOL InitInstance ();
};
CMyWinApp theApp;
BOOL CMyWinApp::InitInstance ()
{
	CMyDlg dlg;
	m_pMainWnd = &dlg;
	dlg.DoModal ();
	return TRUE;
}

DDX的实现原理  

1 控件类型的绑定

DDX_Control (pDX, IDOK, m_wndOK);

void AFXAPI DDX_Control(CDataExchange* pDX, int nIDC, CWnd& rControl)
{// nIDC: IDCOK   , rControl: m_wndOK
	...................................
	// 通过控件ID得到控件句柄
	HWND hWndCtrl = pDX->PrepareCtrl(nIDC);

	if (!rControl.SubclassWindow(hWndCtrl))
	{
		..........................................
	}
}

DDX_Control-->SubclassWindow

BOOL CWnd::SubclassWindow(HWND hWnd)
{// this == m_wndOK, hWnd == 控件句柄
	// 将m_wndOK控件变量与OK按钮句柄绑定
	if (!Attach(hWnd))
		return FALSE;
    ...............................................
}

DDX_Control-->SubclassWindow-->Attach

BOOL CWnd::Attach(HWND hWndNew)
{//this == m_wndOK, hWndNew == 控件句柄
    ......................................
	CHandleMap* pMap = afxMapHWND(TRUE); // create map if not exist
	ASSERT(pMap != NULL);
    // 建立映射关系
	pMap->SetPermanent(m_hWnd = hWndNew, this);
    ........................................
}

DDX_Control-->SubclassWindow-->Attach-->SetPermanent

void CHandleMap::SetPermanent(HANDLE h, CObject* permOb)
{
	.......................................
	// 以控件句柄为键，以变量句柄为值建立映射关系
	m_permanentMap[(LPVOID)h] = permOb;
	.........................................
}

  总结流程如下：

   DDX_Control(pDX,IDOK,m_wndOK);
   {
     //通过控件ID得到控件句柄
     HWND hWndCtrl = pDX->PrepareCtrl(nIDC);
     //将控件句柄与变量绑定
     rControl.SubclassWindow(hWndCtrl);
     {
        Attach(hWnd);
        {
           pMap->SetPermanent(m_hWnd = hWndNew, this);
           {
             //以句柄为健，以变量地址为值建立映射关系
             m_permanentMap[(LPVOID)h] = permOb;
           }
        }
     }
   } 

2 值类型的绑定

UpdateData (FALSE);

BOOL CWnd::UpdateData(BOOL bSaveAndValidate)
{// this == &dlg,  bSaveAndValidate == FALSE
	.............................................

	CDataExchange dx(this, bSaveAndValidate);

	 ..........................................
	 // 虚函数，会调用我们重写的函数
	 DoDataExchange(&dx);
	 ........................................
}

UpdateData-->DoDataExchange-->CMyDlg::DoDataExchange-->DDX_Text

void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, CString& value)
{// pDX中保存了&dlg和FALSE, nIDC == IDOK, value == m_strEdit
	// 通过控件ID拿到编辑框控件句柄
    HWND hWndCtrl = pDX->PrepareEditCtrl(nIDC);
	if (pDX->m_bSaveAndValidate)
	{// UpdateData (TRUE)
		int nLen = ::GetWindowTextLength(hWndCtrl);
		// 获取控件文本
		::GetWindowText(hWndCtrl, value.GetBufferSetLength(nLen), nLen+1);
		value.ReleaseBuffer();
	}
	else
	{// UpdateData (FALSE)
		// 设置控件文本
		AfxSetWindowText(hWndCtrl, value);
	}
}

   UpdateData(FALSE);
   {
      CDataExchange dx(this, bSaveAndValidate);
      DoDataExchange(&dx);
      {
         DDX_Text(pDX,IDC_EDIT1,m_strEdit);
         {
           //通过控件ID得到控件句柄
           HWND hWndCtrl = pDX->PrepareEditCtrl(nIDC);
           if (pDX->m_bSaveAndValidate)
	   {
		
		::GetWindowText(hWndCtrl,...); 
		value.ReleaseBuffer();
	   }
	   else
	   {
                //将变量的值设置到控件的窗口上
		AfxSetWindowText(hWndCtrl, value);
	   }
           
         }
      }
   }

MFC控件数据交换:DDX,布布扣,bubuko.com

MFC控件数据交换:DDX

标签：blog   使用   os   io   数据   for   2014   ar   

原文地址：http://blog.csdn.net/eldn__/article/details/38357643