How to add buttons to a main window in Qt? - qt

Question

I'm new to qt programming so please don't mind if you find it a noob question. I've added a button to my main window but when I run the code the button is not displayed. Here's my code:
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtWidgets>
MainWindow::MainWindow(QWidget *parent)
{
QPushButton *train_button = new QPushButton(this);
train_button->setText(tr("something"));
train_button->move(600, 600);
train_button->show();
}
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
MainWindow::~MainWindow()
{
delete ui;
}
What should I do?

Answer 1

In main window you should use central widget . You have two choices :
Set the button for central widget ( Not so good choice ) :
QPushButton *train_button = new QPushButton(this);
train_button->setText(tr("something"));
setCentralWidget(train_button);
Add a widget and add the button to that widget and set the widget for centralWidget :
QWidget * wdg = new QWidget(this);
QPushButton *train_button = new QPushButton(wdg);
train_button->setText(tr("something"));
setCentralWidget(wdg);
And surely you can use Layouts for your centralWidget:
QWidget * wdg = new QWidget(this);
QVBoxLayout *vlay = new QVBoxLayout(wdg);
QPushButton *btn1 = new QPushButton("btn1");
vlay->addWidget(btn1);
QPushButton *btn2 = new QPushButton("btn2");
vlay->addWidget(btn2);
QPushButton *btn3 = new QPushButton("btn3");
vlay->addWidget(btn3);
wdg->setLayout(vlay);
setCentralWidget(wdg);