Content not getting added \ showing in a QWidget

Question

I'm trying to add content to a QWidget, but nothing ever shows. The window comes out blank, empty without any content I'm trying to include.

mainwindow.cpp

#include "mainwindow.h"

#include <QApplication>

MainWindow::MainWindow(QWidget *parent) :
    QWidget(parent, Qt::FramelessWindowHint | Qt::WindowSystemMenuHint)
{
    mainWin = new QWidget();

    // Create the button, make "this" the parent
    m_button = new QPushButton("My Button", this);
    // set size and location of the button
    m_button->setGeometry(QRect(QPoint(100, 100), QSize(200, 50)));

    hlayout = new QHBoxLayout;
    hlayout -> addWidget(m_button);

    mainWin -> setLayout(hlayout);
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QHBoxLayout>

class MainWindow : public QWidget
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);

private:

    QPushButton *m_button;

    QHBoxLayout *hlayout;
};

#endif

main.cpp

#include "mainwindow.h"
#include <QtPlugin>
#include <QApplication>

#include <QDesktopWidget>

Q_IMPORT_PLUGIN(BasicToolsPlugin)

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow window;

    QDesktopWidget dw;

    int x=dw.width()*0.7;
    int y=dw.height()*0.7;
    window.setFixedSize(x, y);

    window.show();

    return app.exec();
}

What is it that I'm missing, or doing wrong?

Thank you all in advance.

Answer 1

Your code is not complete. I had to make some fixes (includes, declarations) to compile it.

Anyway, to start to see something, you have to either replace:

mainWin = new QWidget();

with

mainWin = new QWidget(this);

or replace:

mainWin -> setLayout(hlayout);

with

this -> setLayout(hlayout);

In the latter case it doesn't make sense calling:

m_button->setGeometry(QRect(QPoint(100, 100), QSize(200, 50)));

since position and size of m_button is handled automatically by the layout.