Subclassing a QWidget

[aguleo]

Hi
I'm trying to understand how to subclass a QWidget.
I want to create a widget with 2 buttons allong with some drawing elements.
How does it work in terms of layout for the subclassed widget.
I ask because aparently the first layout that i use becomes the main layout!
I attach small small example: layoutwidget.zip

[alrawab]

#ifndef DESENHO_H
#define DESENHO_H
 
#include <QWidget>
#include <QVBoxLayout>
#include <QSpacerItem>
#include <QPushButton>
 
 
class Widget : public QWidget
{
    Q_OBJECT
 
public:
    Widget(QWidget *parent = 0);
    ~Widget();
    void draw(QPainter *painter);
 
protected:
    void paintEvent(QPaintEvent *event);
 
private:
    QPushButton *btn1, *btn2;
    QSpacerItem *spacer;
    QVBoxLayout *verticalLayout;
     QHBoxLayout *horizontalLayout;
};
 
#endif

#ifndef DESENHO_H
#define DESENHO_H

#include <QWidget>
#include <QVBoxLayout>
#include <QSpacerItem>
#include <QPushButton>


class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();
    void draw(QPainter *painter);

protected:
    void paintEvent(QPaintEvent *event);

private:
    QPushButton *btn1, *btn2;
    QSpacerItem *spacer;
    QVBoxLayout *verticalLayout;
     QHBoxLayout *horizontalLayout;
};

#endif

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#include <QtGui>
 
#include "widget.h"
 
Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    btn1 = new QPushButton(this);
    btn2 = new QPushButton(this);
    spacer = new QSpacerItem(0,100);
    verticalLayout = new QVBoxLayout(this);
  horizontalLayout=new QHBoxLayout;
  verticalLayout->addStretch(1);
//  horizontalLayout->addItem(spacer);
  horizontalLayout->addWidget(btn1);
  horizontalLayout->addWidget(btn2);
verticalLayout->addLayout(horizontalLayout);
this->setLayout(verticalLayout);
    //verticalLayout->addItem(spacer);
    //verticalLayout->addWidget(btn1);
    //verticalLayout->addWidget(btn2);
}
 
Widget::~Widget()
{
 
}
 
void Widget::paintEvent(QPaintEvent * /* event */)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
 
 
    draw(&painter);
}
 
void Widget::draw(QPainter *painter)
{
 
 
}

#include <QtGui>

#include "widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    btn1 = new QPushButton(this);
    btn2 = new QPushButton(this);
    spacer = new QSpacerItem(0,100);
    verticalLayout = new QVBoxLayout(this);
  horizontalLayout=new QHBoxLayout;
  verticalLayout->addStretch(1);
//  horizontalLayout->addItem(spacer);
  horizontalLayout->addWidget(btn1);
  horizontalLayout->addWidget(btn2);
verticalLayout->addLayout(horizontalLayout);
this->setLayout(verticalLayout);
    //verticalLayout->addItem(spacer);
    //verticalLayout->addWidget(btn1);
    //verticalLayout->addWidget(btn2);
}

Widget::~Widget()
{

}

void Widget::paintEvent(QPaintEvent * /* event */)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);


    draw(&painter);
}

void Widget::draw(QPainter *painter)
{


}

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[Santosh Reddy]

You need to re-implement paintEvent of "some drawing elements" and let the "main layout" take care the laying out pushbuttons and "drawing elements".

[Zlatomir]

You set create a "main" layout and within that you can add another layout if you want to, tell us more about what are you trying to achieve and also take a look at documentation

Also, you can use forward declaration in headers for all classes that have only pointers or references or are passed as parameter to member function (this makes the compilation faster for bigger projects):

#ifndef DESENHO_H
#define DESENHO_H
 
#include <QWidget> //you need this header included because you derive from QWidget
/* you don't need these headers included in your header
-- include those in the .cpp file
#include <QVBoxLayout>
#include <QSpacerItem>
#include <QPushButton>
*/
//here you only use forward declaration:
class QVBoxLayout;
class QPushButton;
//and so on 
class Widget : public QWidget
{
    Q_OBJECT
 
public:
    Widget(QWidget *parent = 0);
    ~Widget();
    void draw(QPainter *painter);
 
protected:
    void paintEvent(QPaintEvent *event);
 
private:
    QPushButton *btn1, *btn2;
    QSpacerItem *spacer;
    QVBoxLayout *verticalLayout;
};
 
#endif

#ifndef DESENHO_H
#define DESENHO_H

#include <QWidget> //you need this header included because you derive from QWidget
/* you don't need these headers included in your header
-- include those in the .cpp file
#include <QVBoxLayout>
#include <QSpacerItem>
#include <QPushButton>
*/
//here you only use forward declaration:
class QVBoxLayout;
class QPushButton;
//and so on 
class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();
    void draw(QPainter *painter);

protected:
    void paintEvent(QPaintEvent *event);

private:
    QPushButton *btn1, *btn2;
    QSpacerItem *spacer;
    QVBoxLayout *verticalLayout;
};

#endif

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