Use of undeclared identifier 'setCentralWidget'

[Troyer]

Hello!
How do I solve this problem related to setCentralWidget? What should I do? I need to display the graph on the tab. I can get it to output to mainwindow.cpp, but not in the other cpp file

[jsulm]

@Troyer Please post text not screen-shots.

setCentralWidget is a method in QMainWindow. What is the base class of your fundction_QPainter class?

[Troyer]

@jsulm I created these classes by simply right-clicking on file - > add new -> and selecting the widget class. So the base class turns out to be QMainWindow

function_qpainter.cpp

#include "function_qpainter.h"
#include "ui_function_qpainter.h"
#include <QtCharts/QChartView>

function_QPainter::function_QPainter(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::function_QPainter)
{
    ui->setupUi(this);
    
    QScatterSeries *series0 = new QScatterSeries();
        series0->setName("Синие точки");
        series0->setMarkerShape(QScatterSeries::MarkerShapeCircle);
        series0->setMarkerSize(15.0);
        QScatterSeries *series1 = new QScatterSeries();
        series1->setName("Зеленые квадраты");
        series1->setMarkerShape(QScatterSeries::MarkerShapeRectangle);
        series1->setMarkerSize(20.0);
        QScatterSeries *series2 = new QScatterSeries();
        series2->setName("Оранжевые звезды");
        series2->setMarkerShape(QScatterSeries::MarkerShapeRectangle);
        series2->setMarkerSize(30.0);
        series0->append(0, 6);
        series0->append(2, 4);
        series0->append(3, 8);
        series0->append(7, 4);
        series0->append(10, 5);
        *series1 << QPointF(1, 1) << QPointF(3, 3) << QPointF(7, 6) << QPointF(8, 3) << QPointF(10, 2);
        *series2 << QPointF(1, 5) << QPointF(4, 6) << QPointF(6, 3) << QPointF(9, 5);
        QPainterPath starPath;
        starPath.moveTo(28, 15);
        for (int i = 1; i < 5; ++i) {
            starPath.lineTo(14 + 14 * qCos(0.8 * i * M_PI),
                            15 + 14 * qSin(0.8 * i * M_PI));
        }
        starPath.closeSubpath();

        QImage star(30, 30, QImage::Format_ARGB32);
        star.fill(Qt::transparent);
        QPainter painter(&star);
        painter.setRenderHint(QPainter::Antialiasing);
        painter.setPen(QRgb(0xf6a625));
        painter.setBrush(painter.pen().color());
        painter.drawPath(starPath);

        series2->setBrush(star);
        series2->setPen(QColor(Qt::transparent));
        QChart *chart = new QChart();
        chart->addSeries(series0);
        chart->addSeries(series1);
        chart->addSeries(series2);
        chart->setTitle("Пример точечной диаграммы");
        chart->createDefaultAxes();
        chart->setDropShadowEnabled(false);
    chart->legend()->setMarkerShape(QLegend::MarkerShapeFromSeries);
        QChartView *chartView = new QChartView(chart);
        chartView->setRenderHint(QPainter::Antialiasing);
        setCentralWidget(chartView);    
    
}

function_QPainter::~function_QPainter()
{
    delete ui;
}

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "function_qpainter.h"
#include "function_qchart.h"
#include "function_qchart_view.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QTabWidget *ptrTabWidget = new QTabWidget(this);
    ptrTabWidget->addTab(new function_QPainter(), "QPainter");
    ptrTabWidget->addTab(new function_qchart(), "QChart");
    ptrTabWidget->addTab(new function_qchart_view(), "QChartView");
    ptrTabWidget->resize(400,600);

}

MainWindow::~MainWindow()
{
    delete ui;
}

[jsulm]

@Troyer said in Use of undeclared identifier 'setCentralWidget':

So the base class turns out to be QMainWindow

This is wrong.
You call setCentralWidget in function_QPainter not in MainWindow. MainWindow is a QMainWindow.
So, again: what is the base class of function_QPainter? Can you show its declaration?

[Troyer]

@jsulm Sorry, i'm new to this app

it is my base class

function_qpainter.h

#ifndef FUNCTION_QPAINTER_H
#define FUNCTION_QPAINTER_H

#include <QWidget>
#include <QtCharts/QtCharts>
#include <QPainterPath>
#include <QtCharts/QLineSeries>
#include <QtCharts/QSplineSeries>

namespace Ui {
class function_QPainter;
}

class function_QPainter : public QWidget
{
    Q_OBJECT

public:
    explicit function_QPainter(QWidget *parent = nullptr);
    ~function_QPainter();

private:
    Ui::function_QPainter *ui;
    
};

#endif // FUNCTION_QPAINTER_H

[jsulm]

@Troyer said in Use of undeclared identifier 'setCentralWidget':

class function_QPainter : public QWidget

As you can see function_QPainter is a QWidget and QWidget does not have setCentralWidget. Why do you try to call setCentralWidget there?

[Troyer]

@jsulm All I want to do is display on the tab (which I'm already very tired of) a graph of the function built in the code. And for some reason, without this 'setCentralWidget' command, it doesn't want to display it on the tab :)

[jsulm]

@Troyer So you want to show your function_QPainter in a tab in ptrTabWidget in MainWindow, right?
You need to call setCentralWidget in MainWindow:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QTabWidget *ptrTabWidget = new QTabWidget(this);
    ptrTabWidget->addTab(new function_QPainter(), "QPainter");
    ptrTabWidget->addTab(new function_qchart(), "QChart");
    ptrTabWidget->addTab(new function_qchart_view(), "QChartView");
    ptrTabWidget->resize(400,600);
    setCentralWidget(ptrTabWidget);
}

[Troyer]

@jsulm Thank you very much :)