Qt5 Custom Widget

I'm currently working on a Qt soft and to make things properly I choose to create some "custom" widgets (which are not). My "custom widget" is usually just a simple class with a lot of widgets in it. I did that because I didn't want to store all of this shitty code lines (to init widgets) in my main window.

The problem is : When I init widget in an other class they don't show up in my main window. I give to my other classes a reference to the main window layout (so I can modify it)

Here is an example :

#ifndef VIDEOCONTROLLERS_H
#define VIDEOCONTROLLERS_H

#include <QGroupBox>
#include <QLayout>
#include <QPushButton>

class VideoControllers : QWidget
{

public:
    VideoControllers(QVBoxLayout &layout);

private:
    QGroupBox _vBox;
    QPushButton _vSpeedDownButton;
    QPushButton _vPrevFrameButton;
    QPushButton _vPlayButton;
    QPushButton _vNextFrameButton;
    QPushButton _vSpeedUpButton;


signals:

public slots:
};

#endif // VIDEOCONTROLLERS_H

Here is the cpp

#include "VideoControllers.hpp"

VideoControllers::VideoControllers(QVBoxLayout& layout) :
    _vSpeedDownButton("s-"),
    _vPrevFrameButton("f-"),
    _vPlayButton("p"),
    _vNextFrameButton("f+"),
    _vSpeedUpButton("s+")
{
    _vBox.setTitle("Video nav");

    QHBoxLayout *globalLayout = new QHBoxLayout;

    globalLayout->addWidget(&_vSpeedDownButton);
    globalLayout->addWidget(&_vPrevFrameButton);
    globalLayout->addWidget(&_vPlayButton);
    globalLayout->addWidget(&_vNextFrameButton);
    globalLayout->addWidget(&_vSpeedUpButton);

    _vBox.setLayout(globalLayout);
    layout.addWidget(&_vBox);
}

The weird thing about this is that when I'm not using a member data widget, all works just fine.

QGroupBox *vBox = new vBox("Video nav");
layout.addWidget(vBox);

This code display me the GroupBox but not the elements that are in it while the other isn't.

I'm a newbie at this but I can't see why my objetcs aren't displayed.

Also please tell me if there are others posts like mine, I didn't know what to search ... :/

Sorry for the english