C++ GUI QSpinBox's not showing up

Question

My program compiles and displays my push buttons correctly but for some reason its not displaying the QSpinBox's. I'm pretty new at C++ qt GUI so any input would be greatly appreciated. I also checked if the spinners were being overlapped by the buttons but they were not.

//
// mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtGui>
#include <QPushButton>
#include <QLabel>
#include <QSpinBox>

namespace Ui {
  class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
private slots:
    void clearx();
    void equalsx();
    void addx();
    void subtractx();
    void multiplyx();
    void dividex();
    void firstnumberx();
    void secondnumberx();
private:
    QLabel *label;
    QPushButton *equal;
    QPushButton *clear;
    QPushButton *equals;
    QPushButton *add;
    QPushButton *subtract;
    QPushButton *multiply;
    QPushButton *divide;
    QSpinBox *spinner;
    QSpinBox *spinner2;
};

#endif // MAINWINDOW_H

//
// mainwindow.cpp

#include "mainwindow.h"
#include <QTCore/QCoreApplication>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)

{
    label = new QLabel("0,this");
    label -> setGeometry(QRect(QPoint(75,75),QSize(50,200)));

    clear = new QPushButton("Clear", this);
    clear  -> setGeometry(QRect(QPoint(80,300),QSize(50,50)));
    connect(clear,SIGNAL(released()),this,SLOT(clearx()));

    equal = new QPushButton("Equal", this);
    equal  -> setGeometry(QRect(QPoint(110,300),QSize(50,50)));
    connect(equal,SIGNAL(released()),this,SLOT(equalx()));

    add = new QPushButton("Add", this);
    add -> setGeometry(QRect(QPoint(140,300),QSize(50,50)));
    connect(add,SIGNAL(released()),this,SLOT(addx()));

    subtract = new QPushButton("Subtract", this);
    subtract -> setGeometry(QRect(QPoint(170,300),QSize(50,50)));
    connect(subtract,SIGNAL(released()),this,SLOT(subtractx()));

    multiply = new QPushButton("Multiply", this);
    multiply -> setGeometry(QRect(QPoint(200,300),QSize(50,50)));
    connect(multiply,SIGNAL(released()),this,SLOT(multiplyx()));

    divide = new QPushButton("Divide", this);
    divide -> setGeometry(QRect(QPoint(230,300),QSize(50,50)));
    connect(divide,SIGNAL(released()),this,SLOT(dividex()));

    spinner = new QSpinBox;
    spinner -> setGeometry(QRect(QPoint(130,150),QSize(50,50)));
    connect(divide,SIGNAL(released()),this,SLOT(firstnumberx()));
    spinner->setRange(1,10);

    spinner2 = new QSpinBox;
    spinner2 -> setGeometry(QRect(QPoint(190,150),QSize(50,50)));
    connect(divide,SIGNAL(released()),this,SLOT(secondnumberx()));
    spinner2->setRange(1,10);
}


void MainWindow::clearx() {}
void MainWindow::equalsx() {}
void MainWindow::addx() {}
void MainWindow::subtractx() {}
void MainWindow::multiplyx() {}
void MainWindow::dividex() {}
void MainWindow::firstnumberx() {}
void MainWindow::secondnumberx() {}
MainWindow::~MainWindow() {}

Answer 1

In order for a widget to display inside another widget, you need to set up a parent-child relationship. The simplest way to do this is to pass a pointer to the parent to the child's constructor as an argument.

For your QSpinBox objects, this is done like so:

spinner = new QSpinBox(this);
spinner2 = new QSpinBox(this);

The rest of your code is very laden with hard-coded geometries. For small GUIs, this might not be a problem but can become a bit of a nightmare to maintain for larger ones. Have you considered using QtDesigner to design your GUI? You might also find the layout management classes helpful in making your GUI designs better maintenance of positions and sizing of child widgets.

Answer 2

Add this as parameter of QSpinBox constructor call.