Russian Qt Forum

#include <QWidget>
#include <QPushButton>

class Window : public QWidget
{
    Q_OBJECT

public:
    explicit Window(QWidget *parent = 0) : QWidget(parent) { }

    void add()
    {
        QPushButton * c = new QPushButton(this);
        c->setGeometry(200, 200, 100, 100);
    }
};

#include <QApplication>
#include "window.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Window w;

    QPushButton * b = new QPushButton(&w);
    b->setGeometry(0, 0, 100, 100);

    QObject::connect(b, &QPushButton::clicked, &w, &Window::add);

    w.showFullScreen();

    return a.exec();
}