Display code output to mainwindow in QT - c++

Question

I have some code that I wrote in geany that distributes a total of 28 numbers to 7 letters.
Here is the code in Geany:
#include <iostream>
#include <time.h>
#include <cstdlib>
using namespace std;
int specialstats()
{
int stats[7], x;
for (x=0;x<7;x++) stats[x]=0;
for (x=0;x<28;x++) stats[rand()%7]++;
cout<<"S: "<<stats[0]<<"\n";
cout<<"P: "<<stats[1]<<"\n";
cout<<"E: "<<stats[2]<<"\n";
cout<<"C: "<<stats[3]<<"\n";
cout<<"I: "<<stats[4]<<"\n";
cout<<"A: "<<stats[5]<<"\n";
cout<<"L: "<<stats[6]<<"\n";
return 0;
}
int main()
{
srand(time(NULL));
specialstats();
return 0;
}
So basically I want to put it into QT and have the output of that code show up in a window. Here is what I have there:
again.pro:
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = again
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
Here is my mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
Here is my main.cpp
#include "mainwindow.h"
#include <QApplication>
#include <QLabel>
#include <iostream>
#include <cstdlib>
#include <time.h>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
int stats[7];
int x;
for (x=0;x<7;x++) stats[x]=0;
for (x=0;x<28;x++) stats[rand()%7]++;
QMainWindow mainWindow;
QLabel *label2 = new QLabel (&mainWindow);
label2->setText("S: "<<stats[0]<<"\n");
std::cout<<"P: \033[1;32m"<<stats[1]<<"\033[0m\n";
std::cout<<"E: \033[1;32m"<<stats[2]<<"\033[0m\n";
std::cout<<"C: \033[1;32m"<<stats[3]<<"\033[0m\n";
std::cout<<"I: \033[1;32m"<<stats[4]<<"\033[0m\n";
std::cout<<"A: \033[1;32m"<<stats[5]<<"\033[0m\n";
std::cout<<"L: \033[1;32m"<<stats[6]<<"\033[0m\n";
mainWindow.show();
return a.exec();
}
And my mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
The errors that I get when I try to run this are, and are in my main.cpp:
/home/administrator/again/main.cpp:20: error: invalid operands of types 'const char [5]' and 'int' to binary 'operator<<'
label2->setText("S: \n"<<stats[0]<<"\n");
^
and,
[main.o] Error 1
What do I do to make the output of this text show up in the window?? In Geany, it outputs to a console and works flawlessly. I just want to try new things out and I am a beginner, so go easy on me.

Answer 1

You cannot concatenate c-style strings with the << operator.
To fix your compile error, change line 20 of main.cpp to e.g.:
label2->setText(QString("S: %1").arg(stats[0]));
QString is the default type to handle strings in Qt. You can find fine documentation about QString here: http://doc.qt.io/qt-5/qstring.html
Besides the compiler error, your code has some issues with how you draw into QMainWindow. Essentially, besides the QMainWindow, you need:
a widget
set the widget as 'centralWidget' of QMainWindow
define a layout for this widget
and add all the QLabels you want to show to this layout
These operations could be done in your MainWindow class. Or as you did, in the main function.
Here is a very crude alternative implementation of your main function. There is still a lot of room for improvement, but it should demonstrate the basic principle.
#include <iostream>
#include <cstdlib>
#include <time.h>
#include <QApplication>
#include <QLabel>
#include <QVBoxLayout>
#include "mainwindow.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
int stats[7] = {1,2,3,4,5,6,7};
QWidget *centralWidget = new QWidget();
QVBoxLayout *layout = new QVBoxLayout(&w);
centralWidget->setLayout(layout);
w.setCentralWidget(centralWidget);
QLabel *label[7];
for (int i=0;i<7;i++) {
label[i] = new QLabel (QString("S: %1").arg(stats[i]));
layout->addWidget(label[i]);
}
return a.exec();
}
If you use QtDesigner, you don't have to worry about how to define the layouts programmatically, but you can use a nice and intuitive tool to help you with the process of designing the layout and appearance of the windows.
QtDesigner generates the *.ui files.