How does Qt QChart realize the drawing of line chart

1. use

Qt5.9 and above;

Add QT += charts to the pro file

. Before using each control of QChart, a namespace must be declared. like:

QT_CHARTS_USE_NAMESPACE
QT_BEGIN_NAMESPACE

The relationship between QChart and QChartView:

The relationship between QChart and QChartView is similar to the relationship between QGraphicsScene and QGraphicsView. QChart itself is the class used to store the controls that need to be displayed, and QChartView is the entrance for human eye recognition and observation.

All changes happen on QChart, but the result of the change is displayed through QChartView

2. The effect is as follows

 

3. The specific implementation is as follows

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
 
#include <QtCharts>
#include <QChartView>
#include <QSplineSeries>
 
QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
 
private slots:
    void on_pushButton_clicked();
 
    void on_pushButton_2_clicked();
 
private:
    Ui::MainWindow *ui;
 
};
 
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
#pragma execution_character_set("utf-8")
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
 
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::on_pushButton_clicked()
{
    QLineSeries *lineSeries = new QLineSeries();        //创建折线系列
 
 
       QChartView *chartView = new QChartView(this);
 
 
       /*为系列里添加100个数据*/
 
       for(quint8 i=0; i<100; i++)
 
       {
 
           lineSeries->append(i,qrand()%300);
 
       }
 
 
       lineSeries->setName("red line");                  //设置系列名称
 
 
       QChart * mChart = new QChart();                          //创建图标对象
 
 
       mChart->addSeries(lineSeries);                  //向图表中添加系列
 
 
       mChart->createDefaultAxes();                       //创建默认的坐标，必须在addSeries之后调用
 
       mChart->setTheme(QChart::ChartThemeDark);           //设置图标主题
 
 
       mChart->setTitle("qrand");                       //设置图标名称
 
 
      // mChart->legend()->hide();                          //隐藏图例，也就是不显示系列名称了
 
 
       chartView->setChart(mChart);                    //向chartView中添加图标
 
 
       chartView->resize(QSize(500,300));              //重新设置chartView的大小
 
 
       chartView->setRenderHints(QPainter::Antialiasing);//消除边缘，看起来平滑一些
 
 
       ui->horizontalLayout->addWidget(chartView);     //把chartView放到水平布局中（在ui中拖一个水平布局）
}
 
void MainWindow::on_pushButton_2_clicked()
{
       QLineSeries *lineSeries = new QLineSeries();        //创建折线系列
       QChartView *chartView = new QChartView(this);
 
       for(quint8 i=0; i<100; i++)
       {
           lineSeries->append(i,qrand()%300);
       }
 
 
       lineSeries->setName("red line");
 
       QChart * mChart = new QChart();
       mChart->addSeries(lineSeries);
 
 
       //mChart->createDefaultAxes();
       QValueAxis *axisX = new QValueAxis;
       axisX->setRange(0, 300); //设置坐标轴范围
       axisX->setTickCount(5); //主分隔个数
       axisX->setMinorTickCount(2);//4
       mChart->addAxis(axisX,Qt::AlignLeft ); //坐标轴添加到图表，并指定方向
       lineSeries->attachAxis(axisX); //序列 series0 附加坐标轴
 
 
       QValueAxis *axisY = new QValueAxis;
       axisY->setRange( 0,  100);
       axisY->setTickCount(10);
       axisY->setMinorTickCount(2);//4
       mChart->addAxis(axisY,Qt::AlignBottom);
       lineSeries->attachAxis(axisY);
 
       mChart->setTheme(QChart::ChartThemeDark);
       lineSeries->setColor(Qt::red);
 
       mChart->setTitle("qrand");
 
       chartView->setChart(mChart);
 
       chartView->resize(QSize(500,300));
 
       chartView->setRenderHints(QPainter::Antialiasing); 
       ui->horizontalLayout->addWidget(chartView);     
}

4. Refresh QChart

//更新系列中的数据  注意：不需要将该系列从图表中移除
    lineSeries->clear();
    QList<QPointF> list;
    int count = cloud.points.size();
    std::cout << "new point s count : " << count << "  " << std::endl;
 
 
    for (int i = 0; i < count; i+=10)
    {
        list << QPointF(cloud.points[i].z, cloud.points[i].y);
    }
    lineSeries->replace(list);

5. PCL point sorting

    //------------------------------排序----------------------------
    std::sort(cloud.begin(), cloud.end(),
        [](pcl::PointXYZ a, pcl::PointXYZ b) {return a.z < b.z; });

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