实现从IE中拖放URL的类

.h文件

#include "oleidl.h"
#include "controls.hpp"
//---------------------------------------------------------------------------
class TMyDropTarget : public IDropTarget
{
public:
    __property void __fastcall (__closure *OnGetFormat)(IDropTarget *Sender,IDataObject *DataObject,DWORD KeyState, TPoint pt, DWORD &dpe,bool &bDataOK) = {read=_FGetFormat,write=_FGetFormat};
    __property void __fastcall (__closure *OnProcessData)(IDropTarget *Sender,IDataObject *DataObject,DWORD KeyState, TPoint pt) = { read=_FProcessData,write=_FProcessData};
    __property void __fastcall (__closure *OnProcessText)(IDropTarget *Sender,AnsiString AText,DWORD KeyState, TPoint pt) = {read=_FProcessText,write=_FProcessText};
    TMyDropTarget(TWinControl *AOwner);
    ~TMyDropTarget();
    HRESULT __stdcall QueryInterface(const GUID &iid,void **ppv);
    ULONG   __stdcall AddRef(void){return ++_iRefCount;}
    ULONG   __stdcall Release(void){if(--_iRefCount==0){delete this;}return _iRefCount;}
    HRESULT __stdcall DragEnter(IDataObject *pDataObject,DWORD grfKeyState,POINTL pt,DWORD *pdwEffect);
    HRESULT __stdcall DragOver(DWORD grfKeyState,POINTL pt,DWORD *pdwEffect);
    HRESULT __stdcall DragLeave(void);
    HRESULT __stdcall Drop(IDataObject *pDataObject,DWORD grfKeyState,POINTL pt,DWORD *pdwEffect);
private:   
    ULONG _iRefCount;
    IDataObject *_lpDataObj;
    TWinControl *_OwnerControl;
    void __fastcall (__closure *_FGetFormat)(IDropTarget *Sender,IDataObject *DataObject,DWORD KeyState,TPoint pt,DWORD &dpe,bool &bDataOK);
    void __fastcall (__closure *_FProcessData)(IDropTarget *Sender,IDataObject *DataObject,DWORD KeyState,TPoint pt);
    void __fastcall (__closure *_FProcessText)(IDropTarget *Sender,AnsiString AText,DWORD KeyState,TPoint pt);
    bool __fastcall FDataFormatOK(DWORD KeyState,POINTL pt,DWORD &dpe);
    void __fastcall FProcessData(DWORD KeyState,POINTL pt);
};

 

.cpp文件

//---------------------------------------------------------------------------
TMyDropTarget::TMyDropTarget(TWinControl *AOwner)   
{
    _OwnerControl = AOwner;
    _iRefCount = 0;
    _lpDataObj = NULL;
    _FGetFormat = NULL;
    _FProcessData = NULL;
    _FProcessText = NULL;
    RegisterDragDrop(_OwnerControl->Handle,this);
}
//---------------------------------------------------------------------------
TMyDropTarget::~TMyDropTarget()
{
    RevokeDragDrop(_OwnerControl->Handle);
}

//---------------------------------------------------------------------------
HRESULT __stdcall TMyDropTarget::QueryInterface(const GUID &iid,void **ppv)
{
    if((iid==IID_IUnknown)||(iid==IID_IDropTarget))
    {
        *ppv=this;
        AddRef();
    }
    else
    {
        *ppv=NULL;
        return E_NOINTERFACE;
    }
    return S_OK;
}

//---------------------------------------------------------------------------
HRESULT __stdcall TMyDropTarget::DragEnter(IDataObject *pDataObject,DWORD grfKeyState,POINTL pt,DWORD *pdwEffect)
{
    _lpDataObj = pDataObject;   
    FDataFormatOK(grfKeyState,pt,*pdwEffect);
    return S_OK;
}   

//---------------------------------------------------------------------------
HRESULT __stdcall TMyDropTarget::DragOver(DWORD grfKeyState,POINTL pt,DWORD *pdwEffect)
{
    FDataFormatOK(grfKeyState,pt,*pdwEffect);
    return   S_OK;
}   

//---------------------------------------------------------------------------
HRESULT __stdcall TMyDropTarget::DragLeave(void)
{
    return S_OK;
}   

//---------------------------------------------------------------------------   
HRESULT __stdcall TMyDropTarget::Drop(IDataObject *pDataObject,DWORD grfKeyState, POINTL pt,DWORD *pdwEffect)
{
    _lpDataObj = pDataObject;
    if(FDataFormatOK(grfKeyState,pt,*pdwEffect))
    FProcessData(grfKeyState,pt);
    return S_OK;
}   

//---------------------------------------------------------------------------   
bool __fastcall TMyDropTarget::FDataFormatOK(DWORD KeyState,POINTL pt,DWORD &dpe)
{   
    FORMATETC fetc={CF_TEXT,0,DVASPECT_CONTENT,-1,DWORD(-1)};
    bool bOK=_lpDataObj->QueryGetData(&fetc)==S_OK;
    /*
        文本拖放:bOK?DROPEFFECT_COPY:DROPEFFECT_NONE;
    */
    dpe = bOK?DROPEFFECT_LINK:DROPEFFECT_NONE;
    if(_FGetFormat)
    {
        TPoint point(pt.x,pt.y);
        ::ScreenToClient(_OwnerControl->Handle,&point);
        _FGetFormat(this,_lpDataObj,KeyState,point,dpe,bOK);
    }
    return bOK;
}

//---------------------------------------------------------------------------
void __fastcall TMyDropTarget::FProcessData(DWORD KeyState,POINTL pt)
{
    if(_FProcessData)
    {
        TPoint point(pt.x,pt.y);
        ::ScreenToClient(_OwnerControl->Handle,&point);
        _FProcessData(this,_lpDataObj,KeyState,point);
    }
    else if(_FProcessText)
    {
        STGMEDIUM smed;
        FORMATETC fetc={CF_TEXT,0,DVASPECT_CONTENT,-1,DWORD(-1)};
        BOOL   bValue=(_lpDataObj->GetData(&fetc,&smed)==S_OK);
        if(bValue)
        {
            HGLOBAL hData = GlobalLock(smed.hGlobal);
            if(hData)
            {
                TPoint point(pt.x,pt.y);
                ::ScreenToClient(_OwnerControl->Handle,&point);
                _FProcessText(this,(char*)hData,KeyState,point);
                GlobalUnlock(hData);
                GlobalFree(hData);
            }
        }
    }
}