//添加海图数据小按钮槽函数

void MainWindow::addChartlayers()

{

　　m_mapCanvas->freeze(true);//冻结或解冻地图画布对象,frozen (true) or thawed (false). Default is true.

    //步骤1：打开文件选择对话框

    QString filename=QFileDialog::getOpenFileName(this,tr("打开海图数据"),"","*.000");

    if(filename.isNull())//如果未选择文件则返回

    {

        return;

    }

    QFileInfo fi(filename);

    QString basename=fi.baseName();//获取文件基名称。基名称：即不包含路径又不包含扩展名的文件名

    //步骤2：创建QgsVectorLayer类

    QgsVectorLayer* layer=new QgsVectorLayer(filename,basename,"ogr",false);

    if(!layer->isValid())//如果图层不合法

    {

        QMessageBox::critical(this,"error","图层无效！");

        return;

    }

    else

    {

　　　　　//QStringList sEncodings = QgsVectorDataProvider::availableEncodings();

        layer->setProviderEncoding( "System"  );//设置图层的编码格式

        QStringList sublayers = layer->dataProvider()->subLayers();//获取用户选择的电子海图所包含的全部子图层的字符串名称

        int subLayersCount=sublayers.count();// If the newly created layer has more than 1 layer of data available, we show the sublayers selection dialog so the user can select the sublayers to actually load.

        if ( subLayersCount >=  )

        {

            for(int i=;i<subLayersCount;i++)

            {

                //注册添加矢量数据，并个并添加到画布中

                QStringList sLayerDefs = sublayers[i].split( ':' );//.000文件中的子图层的字符串名称结构：如0:DSID:Unknown:None和1:BUAARE:15:Point等

                QString composedURI = filename + "|layerid=" + sLayerDefs[] ;

                QString layerName =basename+"@"+sLayerDefs[];

                QString layerGeometryType = sLayerDefs[];//图层类型

                QgsVectorLayer* layerTemp;

                if( !layerGeometryType.isEmpty() && layerGeometryType=="Polygon" && sLayerDefs[]=="LNDARE" )//LNDARE是我的*.000数据中，我打算显示的那个子图层的图层名称

                {

                    composedURI += "|geometrytype=" + layerGeometryType;//设置海图子图层的完全字符串名称

                    layerTemp=new QgsVectorLayer(composedURI,layerName,"ogr",false);

                    if(!layerTemp->isValid())//如果图层不合法

                    {

                        QMessageBox::critical(this,"error","海图子图层无效！");

                        return;

                    }

                    QgsMapLayerRegistry::instance()->addMapLayer(layerTemp,true,true);
　　　　　　　　　　　　//设置该图层的单一渲染风格

                    QgsSymbolV2* symbol = QgsSymbolV2::defaultSymbol(layerTemp->geometryType());//QGis::GeometryType::Polygon

                    symbol->setColor(QColor(,,,));

                    layerTemp->setRendererV2( new QgsSingleSymbolRendererV2(symbol) );

                    m_mapCanvasLayerSet.append(layerTemp);

                    m_mapCanvas->setExtent(layerTemp->extent());//设置显示范围

                }

                else

                {

                    continue;

                }

            }

            delete layer;// The first layer loaded is not useful in that case.

        }

        else

        {

            QString msg = tr( "%1 doesn't have any layers" ).arg( basename );

            QMessageBox::critical(this,"Invalid Data Source",msg);

            delete layer;

        }

    }

    //步骤3：将图层集合添加到画布中

    m_mapCanvas->setLayerSet(m_mapCanvasLayerSet);//设置图层集合

    m_mapCanvas->setVisible(true);//设置是否可见

    m_mapCanvas->freeze(false);//解冻图层

    m_mapCanvas->refresh();//刷新

    //在状态条设置地图的比例尺

    double dCurrScale= m_mapCanvas->scale();

    QString sCurrScale=this->m_scaleEdit->toString(dCurrScale);

    this->m_scaleEdit->setScaleString(sCurrScale);

}