c++ - Qt/C++ QPainter::pen: Painter not active (QPainter::begin: Paint device returned engine == 0, type: 1)

Question

这是我的代码：

    QPaintDevice *paintDevice = this;
    QImage image;
    if (!isEnabled())
    {
        // If the globe covers fully the screen then we can use the faster
        // RGB32 as there are no translucent areas involved.
        QImage::Format imageFormat = ( ui->MarbleWidget_plan->viewport()->mapCoversViewport() )
                                     ? QImage::Format_RGB32
                                     : QImage::Format_ARGB32_Premultiplied;
        // Paint to an intermediate image
        image = QImage( rect().size(), imageFormat );
        image.fill( Qt::transparent );
        paintDevice = ℑ
    }

gp = new GeoPainter ( paintDevice, ui->MarbleWidget_plan->viewport(), ui->MarbleWidget_plan->mapQuality() );
    drawMission();

我正在使用大理石小部件：

http://edu.kde.org/marble/

我正在尝试在这张地图上画画！

这是我的drawMission（）：

void video::drawMission(){

    GeoDataCoordinates France( 2.2, 48.52, 0.0, GeoDataCoordinates::Degree );
    gp->setPen( QColor( 0, 0, 0 ) );
    gp->drawText( France, "France" );

    GeoDataCoordinates Canada( -77.02, 48.52, 0.0, GeoDataCoordinates::Degree );
    gp->setPen( QColor( 0, 0, 0 ) );
    gp->drawText( Canada, "Canada" );

    //A line from France to Canada without tessellation

    GeoDataLineString shapeNoTessellation( NoTessellation );
    shapeNoTessellation << France << Canada;

    gp->setPen( oxygenSkyBlue4 );
    gp->drawPolyline( shapeNoTessellation );

    //The same line, but with tessellation

    GeoDataLineString shapeTessellate( Tessellate );
    shapeTessellate << France << Canada;

    gp->setPen( oxygenBrickRed4 );
    gp->drawPolyline( shapeTessellate );

    //Now following the latitude circles

    GeoDataLineString shapeLatitudeCircle( RespectLatitudeCircle | Tessellate );
    shapeLatitudeCircle << France << Canada;

    gp->setPen( oxygenForestGreen4 );
    gp->drawPolyline( shapeLatitudeCircle );
}

这就是我得到的

QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::fontMetrics: Painter not active
QPainter::fontMetrics: Painter not active
QPainter::setPen: Painter not active
QPainter::fontMetrics: Painter not active
QPainter::fontMetrics: Painter not active
QPainter::setPen: Painter not active
QPainter::setPen: Painter not active
QPainter::setPen: Painter not active

谢谢你的帮助 ！和你的时间