c++ obectarx创建自定义实体并加入新建图层，然后根据图层删除这些自定义实体

您好！针对您的问题，我提供以下的C++代码示例，供参考：

首先，我们需要使用AcDbEntity的派生类来创建自定义实体：

class MyCustomEntity : public AcDbEntity
{
public:
    MyCustomEntity();

    virtual Adesk::Boolean worldDraw(AcGiWorldDraw *mode);
    virtual Acad::ErrorStatus dwgInFields(AcDbDwgFiler* filer);
    virtual Acad::ErrorStatus dwgOutFields(AcDbDwgFiler* filer) const;
    virtual Acad::ErrorStatus dxfInFields(AcDbDxfFiler* filer);
    virtual Acad::ErrorStatus dxfOutFields(AcDbDxfFiler* filer) const;

    // add your own functions here
};

接下来，我们可以在MyCustomEntity类中实现我们自己的绘制函数，例如：

Adesk::Boolean MyCustomEntity::worldDraw(AcGiWorldDraw *mode)
{
    // TODO: implement your own drawing logic here
    return Adesk::kTrue;
}

我们还需要实现AcDbEntity的其他虚函数，以便我们的实体能够正确地序列化和反序列化：

Acad::ErrorStatus MyCustomEntity::dwgInFields(AcDbDwgFiler* filer)
{
    Acad::ErrorStatus es = AcDbEntity::dwgInFields(filer);

    // TODO: read in your entity data from the filer here

    return es;
}

Acad::ErrorStatus MyCustomEntity::dwgOutFields(AcDbDwgFiler* filer) const
{
    Acad::ErrorStatus es = AcDbEntity::dwgOutFields(filer);

    // TODO: write out your entity data to the filer here

    return es;
}

Acad::ErrorStatus MyCustomEntity::dxfInFields(AcDbDxfFiler* filer)
{
    Acad::ErrorStatus es = AcDbEntity::dxfInFields(filer);

    // TODO: read in your entity data from the filer here

    return es;
}

Acad::ErrorStatus MyCustomEntity::dxfOutFields(AcDbDxfFiler* filer) const
{
    Acad::ErrorStatus es = AcDbEntity::dxfOutFields(filer);

    // TODO: write out your entity data to the filer here

    return es;
}

接下来，我们可以创建一个新的图层，并将我们的自定义实体添加到该图层中：

AcDbObjectId addCustomEntityToLayer(MyCustomEntity* entity, const TCHAR* layerName)
{
    AcDbObjectId layerId = AcDbObjectId::kNull;

    // open the layer table for write
    AcDbLayerTable* pLayerTable;
    if (acdbHostApplicationServices()->workingDatabase()->getSymbolTable(pLayerTable, AcDb::kForWrite) == Acad::eOk)
    {
        // check if the layer already exists
        if (pLayerTable->has(layerName))
        {
            // open the layer for write
            AcDbLayerTableRecord* pLayerTableRecord;
            if (pLayerTable->getAt(layerName, pLayerTableRecord, AcDb::kForWrite) == Acad::eOk)
            {
                // set the new entity's layer
                entity->setLayerId(pLayerTableRecord->objectId());
                layerId = pLayerTableRecord->objectId();
                pLayerTableRecord->close();
            }
        }
        else
        {
            // create a new layer
            AcDbLayerTableRecord* pLayerTableRecord = new AcDbLayerTableRecord();
            pLayerTableRecord->setName(layerName);
            pLayerTableRecord->setColorIndex(1);

            // add the layer to the layer table
            if (pLayerTable->add(pLayerTableRecord) == Acad::eOk)
            {
                // set the new entity's layer
                entity->setLayerId(pLayerTableRecord->objectId());
                layerId = pLayerTableRecord->objectId();
            }

            pLayerTableRecord->close();
        }

        // close the layer table
        pLayerTable->close();
    }

    // add the entity to the database
    AcDbObjectId entityId;
    acdbHostApplicationServices()->workingDatabase()->addAcDbEntity(entity, entityId);

    return layerId;
}

最后，我们可以根据图层删除我们的自定义实体：

void deleteCustomEntitiesOnLayer(const TCHAR* layerName)
{
    // open the layer table for read
    AcDbLayerTable* pLayerTable;
    if (acdbHostApplicationServices()->workingDatabase()->getSymbolTable(pLayerTable, AcDb::kForRead) == Acad::eOk)
    {
        // check if the layer exists
        if (pLayerTable->has(layerName))
        {
            // open the layer for write
            AcDbLayerTableRecord* pLayerTableRecord;
            if (pLayerTable->getAt(layerName, pLayerTableRecord, AcDb::kForWrite) == Acad::eOk)
            {
                // get the ID of the layer's entities
                AcDbObjectIdArray entityIds;
                pLayerTableRecord->getEntityIds(entityIds);

                // delete the entities
                for (int i = 0; i < entityIds.length(); i++)
                {
                    AcDbEntity* pEntity;
                    if (acdbOpenObject(pEntity, entityIds[i], AcDb::kForWrite) == Acad::eOk)
                    {
                        pEntity->erase();
                        pEntity->close();
                    }
                }

                pLayerTableRecord->close();
            }
        }

        // close the layer table
        pLayerTable->close();
    }
}

以上代码示例仅供参考，具体实现可能需要根据您的实际需求进行调整。