MFC 拖放

1. 添加一个继承自COleDropTarget的类
2. 添加继承自CObject的拖动信息类
3. 在要实现的控件类里面申明和注册COleDropTarget
4. 在应用程序初始化里面加入AfxOleInit

添加继承自COleDropTarget的类

class COleDropTargetEx : public COleDropTarget
{
public:
    COleDropTargetEx();
    virtual ~COleDropTargetEx();

protected:
//处理OnDropEx消息是必须的，否则OnDrop函数不会被执行
//当然也可以在OnDropEx函数中处理数据
    virtual DROPEFFECT OnDragEnter(CWnd* pWnd, COleDataObject* pDataObject,
        DWORD dwKeyState, CPoint point);
    virtual DROPEFFECT OnDragOver(CWnd* pWnd, COleDataObject* pDataObject,
        DWORD dwKeyState, CPoint point);
    virtual BOOL OnDrop(CWnd* pWnd, COleDataObject* pDataObject,
        DROPEFFECT dropEffect, CPoint point);
    virtual DROPEFFECT OnDropEx(CWnd* pWnd, COleDataObject* pDataObject,
        DROPEFFECT dropEffect, DROPEFFECT dropEffectList, CPoint point);
    virtual void OnDragLeave(CWnd* pWnd);
};

 

.cpp文件

COleDropTargetEx::COleDropTargetEx()
{
}

COleDropTargetEx::~COleDropTargetEx()
{
}

//////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////
DROPEFFECT COleDropTargetEx::OnDragEnter(CWnd* pWnd, COleDataObject* pDataObject,
            DWORD dwKeyState, CPoint point)
{
    ASSERT_VALID(this);
    ASSERT(::IsWindow(pWnd->m_hWnd));

    if (pWnd->IsKindOf(RUNTIME_CLASS(CView)))//if CView,Call base class
        return COleDropTarget::OnDragEnter(pWnd,pDataObject, dwKeyState, point);

    COleDropInfo DropInfo( pDataObject, dwKeyState, 0, 0, point );
    
    return ::SendMessage( pWnd->GetSafeHwnd(), DROPM_DRAGENTER, (WPARAM)&DropInfo, 0 );
}

DROPEFFECT COleDropTargetEx::OnDragOver(CWnd* pWnd, COleDataObject* pDataObject,
            DWORD dwKeyState, CPoint point)
{
    ASSERT_VALID(this);
    ASSERT(::IsWindow(pWnd->m_hWnd));

    if (pWnd->IsKindOf(RUNTIME_CLASS(CView)))//if CView,Call base class
        return COleDropTarget::OnDragOver(pWnd,pDataObject, dwKeyState, point);
    
    COleDropInfo DropInfo( pDataObject, dwKeyState, 0, 0, point );

    return ::SendMessage( pWnd->GetSafeHwnd(), DROPM_DRAGOVER, (WPARAM)&DropInfo, 0 );
}

BOOL COleDropTargetEx::OnDrop(CWnd* pWnd, COleDataObject* pDataObject,
            DROPEFFECT dropEffect, CPoint point)
{
    ASSERT_VALID(this);
    ASSERT(::IsWindow(pWnd->m_hWnd));

    if (pWnd->IsKindOf(RUNTIME_CLASS(CView)))//if CView,Call base class
        return COleDropTarget::OnDrop(pWnd, pDataObject,dropEffect,point);

    COleDropInfo DropInfo( pDataObject, 0, dropEffect, 0, point );

    return ::SendMessage( pWnd->GetSafeHwnd(), DROPM_DROP, (WPARAM)&DropInfo, 0 );
}

DROPEFFECT COleDropTargetEx::OnDropEx(CWnd* pWnd, COleDataObject* pDataObject,
            DROPEFFECT dropEffect, DROPEFFECT dropEffectList, CPoint point)
{
    ASSERT_VALID(this);
    ASSERT(::IsWindow(pWnd->m_hWnd));

    if (pWnd->IsKindOf(RUNTIME_CLASS(CView)))//if CView,Call base class
        return COleDropTarget::OnDropEx( pWnd, pDataObject, dropEffect, dropEffectList, point) ;

    COleDropInfo DropInfo( pDataObject, 0, dropEffect, dropEffectList, point );

    return ::SendMessage( pWnd->GetSafeHwnd(), DROPM_DROPEX, (WPARAM)&DropInfo, 0 );
}

void COleDropTargetEx::OnDragLeave(CWnd* pWnd)
{
    ASSERT_VALID(this);
    ASSERT(::IsWindow(pWnd->m_hWnd));

    if (pWnd->IsKindOf(RUNTIME_CLASS(CView)))//if CView,Call base class
    {
        COleDropTarget::OnDragLeave( pWnd );
        return;
    }

    ::SendMessage( pWnd->GetSafeHwnd(), DROPM_DRAGLEAVE, 0, 0 );

    return;
}

 

 

添加继承自CObject的拖动信息类

class COleDropInfo : public CObject
{
public:
    COleDropInfo();
    COleDropInfo(COleDataObject* pDataObject,DWORD dwKeyState,
        DROPEFFECT dropEffect,DROPEFFECT dropEffectList,CPoint point );
    virtual ~COleDropInfo();

public:
    //COleDropTargetEx member functions params
    COleDataObject* m_pDataObject;
    DWORD m_dwKeyState;
    DROPEFFECT m_dropEffect;
    DROPEFFECT m_dropEffectList;
    CPoint m_point;

    DECLARE_DYNAMIC( COleDropInfo );
};

 

.cpp文件

IMPLEMENT_DYNAMIC( COleDropInfo, CObject );

COleDropInfo::COleDropInfo()
{
    m_pDataObject = NULL;
    m_dwKeyState = 0;
    m_dropEffect = (DROPEFFECT)-1;
    m_dropEffectList = DROPEFFECT_NONE;
}

COleDropInfo::COleDropInfo(COleDataObject* pDataObject,DWORD dwKeyState,
                DROPEFFECT dropEffect,DROPEFFECT dropEffectList,CPoint point )
{
    m_pDataObject = pDataObject;
    m_dwKeyState = dwKeyState;
    m_dropEffect = dropEffect;
    m_dropEffectList = dropEffectList;
    m_point = point;
}

COleDropInfo::~COleDropInfo()
{
    m_pDataObject = NULL;
}

 

在要实现拖放功能的控件类里面注册COleDropTarget

class CDropEdit : public CEdit
{
public:
    CDropEdit();

public:
    BOOL m_bDraging;
    virtual BOOL Register();
    virtual ~CDropEdit();

protected:
    COleDropTargetEx m_dropEx;
//处理OnDropEx消息是必须的，否则OnDrop函数不会被执行
//当然也可以在OnDropEx函数中处理数据
    virtual BOOL OnDrop(WPARAM pDropInfoClass, LPARAM lParm);
    virtual DROPEFFECT OnDropEx(WPARAM pDropInfoClass, LPARAM lParm);
    virtual DROPEFFECT OnDragOver(WPARAM pDropInfoClass,LPARAM lParm);
    virtual void OnDragLeave(CWnd* pWnd );

    DECLARE_MESSAGE_MAP()
};

 

.cpp文件

BEGIN_MESSAGE_MAP(CDropEdit, CEdit)
    //{{AFX_MSG_MAP(CDropEdit)
    ON_WM_LBUTTONDOWN()
    //}}AFX_MSG_MAP
    ON_MESSAGE(DROPM_DRAGOVER,OnDragOver)
    ON_MESSAGE(DROPM_DROPEX,OnDropEx)
    ON_MESSAGE(DROPM_DROP,OnDrop)
    ON_MESSAGE(DROPM_DRAGLEAVE,OnDragLeave)
END_MESSAGE_MAP()

CDropEdit::CDropEdit()
{
    m_bDraging = FALSE;
}

CDropEdit::~CDropEdit()
{
}

BOOL CDropEdit::Register()
{
    return m_dropEx.Register( this );
}

void CDropEdit::OnDragLeave(CWnd* pWnd )
{    
}

DROPEFFECT CDropEdit::OnDragOver(WPARAM pDropInfoClass, LPARAM lParm)
{
    this->SetFocus();
    COleDropInfo* pInfo = (COleDropInfo* )pDropInfoClass;
    ASSERT(pInfo->IsKindOf(RUNTIME_CLASS(COleDropInfo)));

    if( pInfo->m_pDataObject->IsDataAvailable( CF_TEXT ) )
        return DROPEFFECT_COPY;
    else
        return DROPEFFECT_NONE;
}

DROPEFFECT CDropEdit::OnDropEx(WPARAM pDropInfoClass, LPARAM lParm)
{
    return (DROPEFFECT)-1;
}

BOOL CDropEdit::OnDrop(WPARAM pDropInfoClass, LPARAM lParm)
{
    COleDropInfo* pInfo = (COleDropInfo* )pDropInfoClass;
    ASSERT(pInfo->IsKindOf(RUNTIME_CLASS(COleDropInfo)));

    if( pInfo->m_pDataObject->IsDataAvailable( CF_TEXT ) )
    {
        HGLOBAL hMem = pInfo->m_pDataObject->GetGlobalData( CF_TEXT );
        char* lp = (char *)GlobalLock((HGLOBAL) hMem);//lock source
        if (lp != NULL)
        {
            //Set Windows title with Drop text 
            SetWindowText( lp );
        }
        GlobalUnlock( hMem );//unlock source
        return TRUE;
    }
    else
        return FALSE;
}

void CDropEdit::OnLButtonDown(UINT nFlags, CPoint point) 
{
    CEdit::OnLButtonDown(nFlags, point);

    //确信要拖动,而不是随便点击
    //按下左键250ms则认为要拖动
    Sleep(250);
    MSG msg;
    ::PeekMessage(&msg,GetSafeHwnd(),WM_LBUTTONUP,WM_LBUTTONUP,PM_NOREMOVE);
    //随意点击而已,返回
    if( msg.message==WM_LBUTTONUP )return;

    CString sContens;
    GetWindowText( sContens );
    HGLOBAL hData = GlobalAlloc(GHND|GMEM_SHARE, sContens.GetLength()+1 );
    char *pS = (char *)GlobalLock( hData );
    memcpy( pS, (LPCTSTR)sContens, sContens.GetLength()+1 );
    GlobalUnlock( hData );

    m_bDraging = TRUE;    //开始拖动
    COleDataSource source;
    source.CacheGlobalData( CF_TEXT, hData );
    source.DoDragDrop( DROPEFFECT_COPY );
    GlobalFree( hData );
    m_bDraging = FALSE;    //完成拖动
}

 

在应用程序初始化函数里面添加OLE初始化

BOOL CDropExDemoApp::InitInstance()
{
    if( !AfxOleInit() )//初始化OLE
        TRACE("Ole init faile");

#ifdef _AFXDLL
    Enable3dControls();
#else
    Enable3dControlsStatic();
#endif

    CDropExDemoDlg dlg;
    m_pMainWnd = &dlg;
    int nResponse = dlg.DoModal();
    if (nResponse == IDOK)
    {}
    else if (nResponse == IDCANCEL)
    {}
    return FALSE;
}

 

相关参考:
MSDN(vc6)地址：Visual C++ Documentation->Using Visual C++->Visual C++ Programmer's Guide->Adding Program Functionality->Details->OLE Topics->Drag and Drop(OLE)
MSDN地址：http://msdn.microsoft.com/en-us/library/aa294159(VS.60).aspx
控件接收文件拖放