把其它程序(如网页等)的文字拖放到Memo里

原作者：Victor Chen

来源：C++ 爱好者

网址: http://www.cppfans.com/

Email: victor@cppfans.com

需要用 COM 接口的 OLE 拖放目标, 程序新建一个支持拖放目标的UnitTMyDropTarget 单元, 在这个单元里创建一个 TMyDropTarget 类。

这个程序可以使从写字板或者网页等定义的文本块用鼠标拖动, 放到程序的 Memo 里, 插入到 Memo 的拖放的位置。

首先看看如何使用这个 TMyDropTarget 类:

在 Form 的头文件里 (例如 Unit1.h) 需要增加的内容(蓝色部分是新增内容):

#include "UnitTMyDropTarget.h"

class TForm1 : public TForm

{

private: // User declarations

TMyDropTarget *DropMemo1; //自定义的拖放目标类

void __fastcall DropMemo1Text(IDropTarget *Sender, AnsiString AText, DWord KeyState, TPoint pt); //拖放事件

public: // User declarations

__fastcall TForm1(TComponent* Owner);

__fastcall ~TForm1();

};

在 From 的 .cpp 文件里 (例如 Unit1.cpp), 需要增加的内容(蓝色部分是新增内容):

__fastcall TForm1::TForm1(TComponent* Owner)

: TForm(Owner)

{

OleInitialize(NULL);

DropMemo1 = new TMyDropTarget(Memo1);

DropMemo1->OnProcessText = DropMemo1Text;

}

//---------------------------------------------------------------------------

__fastcall TForm1::~TForm1()

{

DropMemo1->Release();//delete DropMemo1;

OleUninitialize();

}

//---------------------------------------------------------------------------

void __fastcall TForm1::DropMemo1Text(IDropTarget *Sender, AnsiString AText, DWORD KeyState, TPoint pt)

{

POINTS p={pt.x,pt.y};

*(long*)&p=SendMessage(Memo1->Handle,EM_CHARFROMPOS,0,*(long*)&p);

Memo1->SelStart = p.x;

Memo1->SelLength = 0;

Memo1->SelText = AText;

}

//---------------------------------------------------------------------------

TMyDropTarget 类的实现:

头文件 UnitTMyDropTarget.h 的内容:

//---------------------------------------------------------------------------

#ifndef UnitTMyDropTargetH

#define UnitTMyDropTargetH

//---------------------------------------------------------------------------

#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);

};

//---------------------------------------------------------------------------

#endif

//---------------------------------------------------------------------------

UnitTMyDropTarget.cpp 的内容:

//---------------------------------------------------------------------------

#include "UnitTMyDropTarget.h"

//---------------------------------------------------------------------------

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)

{

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