The Qt program runs but the popup window doesn't display anything

lldn8991

This is the Header file

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QWidget>
#include <QSpinBox>
#include <QSlider>
#include <QDial>
#include <QProgressBar>

class MainWindow : public QMainWindow 
{
    Q_OBJECT
private:
    QSpinBox *spinbox;
    QSlider *slider1;
    QDial *dial;
    QProgressBar *progressbar;

public:
    MainWindow();
/    /~MainWindow();
};
#endif // MAINWINDOW_H

This is the MainWindow file

#include "mainwindow.h"
#include <QVBoxLayout>
#include <QGridLayout>

MainWindow::MainWindow()
{
    spinbox = new QSpinBox;
    slider1 = new QSlider(Qt::Horizontal);
    dial = new QDial;
    progressbar = new QProgressBar;

    QVBoxLayout *lay1 = new QVBoxLayout(this);
   //QGridLayout *lay1 = new QGridLayout(this);

    lay1 -> addWidget(spinbox);
    lay1 -> addWidget(slider1);
    lay1 -> addWidget(dial);
    lay1 -> addWidget(progressbar);

    setLayout(lay1);
}

This is the Main file

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}

SGaist

Hi and welcome to devnet,

QMainWindow already has a layout.

What you can do is create a QWidget where you apply your layout and set it as central widget.