/***********************添加一条线并设置为蓝色，线的区域用半透明蓝色填充****************************/
    customPlot->addGraph();
    customPlot->graph(0)->setPen(QPen(QColor(40, 110, 255)));
//    customPlot->graph(0)->setBrush(QBrush(QColor(0, 0, 255, 20)));//线下方区域用半透明蓝色填充