物联网（X）：QCustomPlot

1. 添加源文件和头文件
2. greaterThan(QT_MAJOR_VERSION, 4): QT += widgets printsupport添加打印支持
3. 在界面新建widget并且提升为qcustomplot

void MainWindow::create(QCustomPlot* customPlot){
    QVector x(101),y(101);
    for(int i=0;i<101;i++){
        x[i]=i/50.0-1;
        y[i]=x[i]*x[i];
    }
    customPlot->addGraph();
    customPlot->graph(0)->setData(x,y);
    customPlot->yAxis->setLabel("x");
    customPlot->xAxis->setLabel("y");
    customPlot->yAxis->setRange(0,1);
    customPlot->xAxis->setRange(-1,1);
}

void MainWindow::setupRealtimeDataDemo(QCustomPlot *customPlot)//实时显示
{

  customPlot->addGraph(); //在面板添加曲线
  customPlot->graph(0)->setPen(QPen(QColor(40, 110, 255)));//曲线颜色

  QSharedPointer timeTicker(new QCPAxisTickerTime);//智能指针
  timeTicker->setTimeFormat("%h:%m:%s");//对指针设置时间格式
  customPlot->xAxis->setTicker(timeTicker);//x的坐标区间
  customPlot->axisRect()->setupFullAxesBox();//坐标轴撑满面板
  customPlot->yAxis->setRange(-1.2, 1.2);//y坐标范围

  connect(customPlot->xAxis, SIGNAL(rangeChanged(QCPRange)), customPlot->xAxis2, SLOT(setRange(QCPRange)));
  connect(customPlot->yAxis, SIGNAL(rangeChanged(QCPRange)), customPlot->yAxis2, SLOT(setRange(QCPRange)));

  connect(&dataTimer, SIGNAL(timeout()), this, SLOT(realtimeDataSlot()));//当定时器溢出之后
  dataTimer.start(0); //开启定时器
}


void MainWindow::realtimeDataSlot()
{
  static QTime timeStart = QTime::currentTime();//从当前时间开始
  double key = timeStart.msecsTo(QTime::currentTime())/1000.0;
  static double lastPointKey = 0;
  if (key-lastPointKey > 0.002)//每2毫秒添加一个点
  {
    ui->widget->graph(0)->addData(key,qSin(key/0.3843));//添加一个点
    lastPointKey = key;
  }
  ui->widget->xAxis->setRange(key, 10, Qt::AlignRight);//位置，大小，对齐
  ui->widget->replot();
}