Class object in mainwindow.h in Qt - c++

Question

I am trting to open a new window (window with the cubeview view in qt3d application) whenever a button is clicked on the main window.
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "cubeview.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
int getid();
public slots:
void pattern1();
private:
CubeView *view;
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
and mainwindow .cpp file
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPushButton>
#include <iostream>
#include "cubeview.h"
int pattern_id;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QPushButton *button= new QPushButton("Pattern 1");
QObject::connect(button, SIGNAL(clicked()), this, SLOT(pattern1()));
button->show();
std::cout<<"reached mainwindow constructor"<<std::endl;
//view= new CubeView;
}
void MainWindow::pattern1()
{
pattern_id=1;
view->begin(1);
view->resize(800, 600);
view->show();
std::cout<<pattern_id<<std::endl;
}
int MainWindow::getid()
{
return pattern_id;
}
MainWindow::~MainWindow()
{
delete ui;
delete view;
}
I get a runtime error.
I hope you get what i am trying to do. Whenever i click on the push button, the cubeview view window should show up. What is the mistake i am making?
Where should I define the cubeView class object so that I can use it later.
Can I initialize it as CubeView *view= new CubeView; in a header file.
I tried to write it in the constructor of mainwindow.cpp
but i get a runtime error.
#ifndef CUBEVIEW_H
#define CUBEVIEW_H
#include "qglview.h"
#include "qgltexture2d.h"
QT_BEGIN_NAMESPACE
class QGLSceneNode;
QT_END_NAMESPACE
//! [1]
class CubeView : public QGLView
{
//! [1]
Q_OBJECT
public:
CubeView(QWidget *parent = 0);
~CubeView();
void begin(int pattern_id);
public slots:
void update_action();
protected:
void paintGL(QGLPainter *painter);
//! [2]
private:
QGLSceneNode *cube;
QGLSceneNode *cursor;
QGLTexture2D logo;
QGLTexture2D* texture;
QGLTexture2D handcursor;
};
//! [2]
#endif
//! [1] constructor, initialize the cube, cursor and camera
CubeView::CubeView(QWidget *parent)
{
//! [1] draw the paintboard
QVector3D *cube1_pos= new QVector3D(0.0,0.0,-1.5);
QGLBuilder builder1;
builder1 << QGL::Faceted;
builder1 << QGLCube(3.25);
cube = builder1.finalizedSceneNode();
cube->setPosition(*cube1_pos);
//draw the cursor
QGLBuilder cursor_builder;
cursor_builder <<QGL::Faceted;
cursor_builder <<QGLCube(0.15);
cursor=cursor_builder.finalizedSceneNode();
//camera setup
camera()->setFieldOfView(35);
camera()->setNearPlane(1);
camera()->setFarPlane(15);
//! [2] set texture for cube and cursor
//QImage image(QLatin1String(":/bluecircle.jpg"));
handcursor.setImage(QImage(QLatin1String(":/hand.jpg")));
std::cout<<"constructor called"<<std::endl;
}

Answer 1

I think I finally found my answer. It has nothing to to do with the definition of the cubeview class constructor. The simple principle is that
-> we need not create a class object within a loop or the program code crashes.
-> also the view.show if directly put inside a connect slot , will run into the error of an infinite loop.
Here is the answer.
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPushButton>
#include <iostream>
#include "cubeview.h"
int pattern_id;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
view=0;
std::cout<<"reached mainwindow constructor"<<std::endl;
QPushButton *button= new QPushButton("Pattern 1");
QObject::connect(button, SIGNAL(clicked()), this, SLOT(pattern1()));
button->show();
else if(view!=NULL)
{
std::cout<<"view is already initialized"<<std::endl;
}
}
void MainWindow::pattern1()
{
if(view==NULL)
{
view=new CubeView;
view->begin(1);
view->resize(800, 600);
view->show();
}
}
int MainWindow::getid()
{
return pattern_id;
}
MainWindow::~MainWindow()
{
delete ui;
delete view;
}
In this way, the new object window is created if the value is already NULL.