在生成的示例程序里，我是在void initApp()里新增了一个命令 acedRegCmds->addCommand(ACRX_T("ASDK_SAMPLES_HELLOARX"),
ACRX_T("ASDK_test"), ACRX_T("test"), ACRX_CMD_MODAL,
TestXData);

该命令的实现代码为

AcDbObjectId appendEnt(AcDbEntity* _pEnt)

{

    AcDbDatabase* pAcDb=acdbHostApplicationServices()->workingDatabase();

    AcDbBlockTable* pBlkTbl;

    pAcDb->getBlockTable(pBlkTbl, AcDb::kForRead);

    AcDbBlockTableRecord* pBlkTblRec;

    pBlkTbl->getAt(ACDB_MODEL_SPACE, pBlkTblRec, AcDb::kForWrite);

    pBlkTbl->close();

    AcDbObjectId id;

    Acad::ErrorStatus es = pBlkTblRec->appendAcDbEntity(id, _pEnt);

    if (es != Acad::eOk)

    {

        pBlkTblRec->close();

        delete _pEnt;

        _pEnt = NULL;

        return AcDbObjectId::kNull;

    }

    pBlkTblRec->close();

    _pEnt->close();

    actrTransactionManager->queueForGraphicsFlush();//刷新显示

    actrTransactionManager->flushGraphics();

    acedUpdateDisplay();

    return id;

}

AcString _AC_STR_(QString qstr)

{

    return AcString((const char*)qstr.toUtf8(), AcString::Utf8);

}

AcString _AC_STR_(char* str)

{

    return AcString((const char*)str, AcString::Utf8);

}

QString _T_(ACHAR* str)

{

    return QString::fromStdWString(str);

}

char *_SZ_(QString _qstr)

{

    char *str;

    QByteArray ba = _qstr.toLocal8Bit() ;//不可以 _qstr.toLocal8Bit().data() ，如果这样，可能会出错

    str = ba.data();

    char *ret = new char[strlen(str) +1];

    strcpy(ret,str);

    return ret;

}

void TestXData()

{

    Acad::ErrorStatus es;

    AcGePoint3d pt1(0, 0, 0), pt2(100, 500, 0);

    AcDbLine* pLine = new AcDbLine(pt1, pt2);

    AcDbObjectId id = appendEnt(pLine);

    es = acdbOpenObject(pLine, id, AcDb::kForWrite);

    if (es != Acad::eOk)

    {

        acutPrintf(ACRX_T("\nError to acdbOpenObject"));

        return;

    }

    QString strRegApp = "appreg",

            strData1 = "Dat1",

            strData2 = "Dat2";

    acdbRegApp(_AC_STR_(strRegApp));

    struct resbuf* rb = acutBuildList(AcDb::kDxfRegAppName, _SZ_(strRegApp),

        AcDb::kDxfXdAsciiString, _SZ_(strData1),

        AcDb::kDxfXdAsciiString, _SZ_(strData2),

        RTNONE);

    pLine->setXData(rb);

    acutRelRb(rb);

    pLine->close();

    AcDbBlockTable *pBlkTbl_read;

    acdbHostApplicationServices()->workingDatabase()->getBlockTable(pBlkTbl_read, AcDb::kForRead);

    AcDbBlockTableRecord *pBlkTblRec_read;

    pBlkTbl_read->getAt(ACDB_MODEL_SPACE, pBlkTblRec_read, AcDb::kForRead);

    if(pBlkTbl_read)pBlkTbl_read->close();

    AcDbBlockTableRecordIterator *pltr;

    pBlkTblRec_read->newIterator(pltr);

    AcDbEntity *pEnt_read;

    for(pltr->start();!pltr->done();pltr->step())

    {

        pltr->getEntity(pEnt_read, AcDb::kForRead);

        if (pEnt_read->isKindOf(AcDbLine::desc()))// 符合条件的 多义线 作为判断的依据

        {

                AcDbLine *pLine_read = AcDbLine::cast(pEnt_read);//whether it's a line

                if(pLine_read != NULL)

                {

                        QString  strData1_read, strData2_read;

                        struct resbuf *pRb_read = pEnt_read->xData(_AC_STR_(strRegApp));//获取实体的扩展数据

                        if (pRb_read != NULL)

                        {

                            struct resbuf *pTemp_read = pRb_read; //使用临时的结果缓冲区指针进行遍历，pRb不修改便于释放

                            if(pTemp_read)pTemp_read = pTemp_read->rbnext;

                            if(pTemp_read)strData1_read = _T_(pTemp_read->resval.rstring);

                            if(pTemp_read)pTemp_read = pTemp_read->rbnext;

                            if(pTemp_read)strData2_read = _T_(pTemp_read->resval.rstring);

                            QMessageBox::information(NULL,"info","acdbline::cast ok\r\ndata1=" + strData1_read +"\r\ndata2="+strData2_read);

                        }

                        else

                        {

                            QMessageBox::information(NULL,"info","acdbline::cast ok, but resbuf read return null");

                        }

                        acutRelRb(pRb_read);

                }

                else

                {

                    QMessageBox::information(NULL,"info","acdbline::cast error");

                }

                if(pLine_read)pLine_read->close();

        }

        if(pEnt_read)pEnt_read->close();

    }

    delete pltr;

    if(pBlkTblRec_read)pBlkTblRec_read->close();

    QMessageBox::information(NULL,"info","test over...");

}

当在cad里test命令时，总是得到 QMessageBox::information(NULL,"info","acdbline::cast ok, but resbuf read return null");不知道是什么原因导致读取不到里面的数据，麻烦赐教，谢谢