qwt横轴为时间轴，纵轴为随机数

#include "mainwindow.h"

#include "ui_mainwindow.h"

#include "qwt_date_scale_draw.h"

#include "qwt_plot.h"

#include <qdatetime.h>

#include <QDateTime>

#include <qwt_plot_magnifier.h>

#include <QTimer>

#include <qwt_symbol.h>

#include <QPoint>

#include <qwt_plot_grid.h>

#include <qwt_plot_curve.h>

QDateTime m_baseTime;

QVector<double> m_xTime;

QVector<double> m_yVal;

QwtPlotCurve *plotcurve;

int m_timeAreaWidth;

QVector<QPointF> m_vp;

double m_timeData[3600];

class TimeScakeDrawR1: public QwtScaleDraw

{

    public:

    TimeScakeDrawR1(const QDateTime &base):

      baseTime(base){

    }

    virtual QwtText label(double v) const

    {

      QDateTime upTime = baseTime.addSecs((int )v);

//    return upTime.toString("yyyy-MM-dd\nhh:mm:ss");

      return upTime.toString("hh:mm:ss");

    }

    private:

    QDateTime baseTime;

};

MainWindow::MainWindow(QWidget *parent) :

    QMainWindow(parent),

    ui(new Ui::MainWindow)

{

    ui->setupUi(this);

    m_timeAreaWidth = 60;

    m_baseTime = QDateTime::currentDateTime();

    QwtPlotGrid *grid = new QwtPlotGrid;//网格

    grid->enableX(true);

    grid->enableY(true);

    grid->setMajorPen(Qt::red,0,Qt::DotLine);

    grid->attach(ui->qwtPlot);

    plotcurve = new QwtPlotCurve();

    plotcurve->setTitle("氨气");//曲线名字

    plotcurve->setPen( Qt::darkCyan, 2 );//曲线的颜色 宽度;

    ui->qwtPlot->setAxisScaleDraw(QwtPlot::xBottom, new TimeScakeDrawR1(m_baseTime));

    ui->qwtPlot->setAxisScale(QwtPlot::yLeft, 0,200,20);

    (void) new QwtPlotMagnifier(ui->qwtPlot->canvas());//可以放大放

    plotcurve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,

        QPen(Qt::blue), QSize(5, 5) ) );

    QTimer *timer = new QTimer(this);

    timer->start(1000);

    connect(timer,SIGNAL(timeout()),this,SLOT(replotCurves()));

}

MainWindow::~MainWindow()

{

    delete ui;

}

void MainWindow::replotCurves()

{

    QPointF pt;

    qint64 timeVal = (QDateTime::currentDateTime().toMSecsSinceEpoch()-m_baseTime.toMSecsSinceEpoch())/1000;

    if(m_vp.size() >= m_timeAreaWidth)

    {

        m_vp.pop_front();

    }

    pt.setX(timeVal);

    pt.setY(rand()%200);

    m_vp.append(pt);

    qint64 k = timeVal;

    for ( int j = 0; j < m_timeAreaWidth; j++ )

    {

        m_timeData[j] = k--;

    }

    ui->qwtPlot->setAxisScale(QwtPlot::xBottom, m_timeData[m_timeAreaWidth - 1 ], m_timeData[0]);

    plotcurve->setSamples(m_vp);

    plotcurve->attach(ui->qwtPlot);

    ui->qwtPlot->replot();

}