最近项目中用到了OLE 拖拽功能

和BCB 一个Form的Drag 不同的是，只有实现了OLE 拖拽才能，从其他程序拖拽数据到Form

下面的代码实现了，同HTML网页拖拽到Form时，Form获得HTML数据

 

其核心思想是，

1，要实现 COM的 IDropTarget 接口

2，RegisterDragDrop(handle,this); 注册窗口的拖拽

3，窗口类构造 OleInitialize(NULL);

4，窗口类析构时 OleUninitialize();

5，在下面的代码中，我将IDropTarget  接口封装为类TOleDragAndDrop

 

//---------------------------------------------------------------------------#include 
     
      #pragma hdrstop#include "Unit1.h"#include 
      
       #include 
       
        #include 
        
         //---------------------------------------------------------------------------#pragma package(smart_init)#pragma resource "*.dfm"TForm1 *Form1;/*实现IDropTarget COM接口*/class TOleDragAndDrop :                        public TObject,                        public IDropTarget,                        public IUnknown{    private:        HANDLE d_handle;//注册的窗体句柄        volatile LONG d_ref; //引用计数器    public:    //构造是注册OLEDragDrop    TOleDragAndDrop(HANDLE handle)    {        d_ref = 0;        d_handle = handle;        RegisterDragDrop(handle,this);    }    //必须虚函数，以调用父类的析构    __fastcall ~TOleDragAndDrop()    {        RevokeDragDrop(d_handle);        //调用父类的析构    }    //实现COM要求的QueryInterface    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void ** ppvObject)    {        HRESULT result=S_OK;        if (GetInterface(iid,ppvObject))            result=S_OK;        else            result=E_NOINTERFACE;        return result;    }    //实现COM要求的引用计数器    ULONG STDMETHODCALLTYPE AddRef(void)    {        ULONG result = InterlockedDecrement(&d_ref);        return result;    }    //实现COM要求的释放接口    ULONG STDMETHODCALLTYPE Release(void)    {        ULONG result = InterlockedDecrement(&d_ref);        return result;    }    //实现IDropTarget 中的DragOver    HRESULT STDMETHODCALLTYPE DragOver(DWORD grfKeyState,        POINTL pt,DWORD *pdwEffect)    {        //ShowMessage("drag over");        return S_OK;    }    //实现IDropTarget 中的DragEnter    HRESULT STDMETHODCALLTYPE DragEnter(IDataObject * pDataObject,        DWORD grfKeyState, POINTL pt,DWORD * pdwEffect)    {        //ShowMessage("drag enter");        return S_OK;    }    //实现IDropTarget 中的DragLeave    HRESULT STDMETHODCALLTYPE DragLeave(void)    {        //ShowMessage("drag leave");        return S_OK;    }    //实现IDropTarget 中的Drop     HRESULT STDMETHODCALLTYPE Drop(IDataObject *pDataObj,DWORD grfKeyState,        POINTL pt,DWORD __RPC_FAR *pdwEffect)    {        AnsiString retStr;        FORMATETC format;        int cf_html = RegisterClipboardFormat("HTML Format");        FORMATETC cFmt = {(CLIPFORMAT) CF_TEXT, NULL, DVASPECT_CONTENT, -1, TYMED_HGLOBAL};        cFmt.cfFormat = cf_html;        STGMEDIUM stgMedium;        pDataObj->GetData(&cFmt, &stgMedium);        if(stgMedium.tymed == TYMED_HGLOBAL)        {            char* html = (char*)GlobalLock(stgMedium.hGlobal);            ShowMessage(Utf8ToAnsi(html));            //剩下的就是把
         。。。 通过XML解析出来        }        return S_OK;    }};//---------------------------------------------------------------------------static TOleDragAndDrop* d_poledragDrop = NULL;__fastcall TForm1::TForm1(TComponent* Owner)    : TForm(Owner){    OleInitialize(NULL);    d_poledragDrop = new TOleDragAndDrop(Memo1->Handle);}//---------------------------------------------------------------------------//---------------------------------------------------------------------------void __fastcall TForm1::FormDestroy(TObject *Sender){    delete d_poledragDrop;    d_poledragDrop = NULL;    OleUninitialize();}//---------------------------------------------------------------------------