Solved Create An object that draw a circle (QPainter)

[yczo]

Hello all, I would like to create a circles matrix in MainWindow. With this purpose, I want to create an objet that draws a circle in MainWindow. I don't reach. Please can somebody help me to fix my code?

Thanks in advance

(ampel.h)
//*********************************************
#ifndef AMPEL_H
#define AMPEL_H
#include <QWidget>

class ampel : public QWidget
{
public:
explicit ampel(QWidget *parent = 0);
protected:
void paintEvent(QPaintEvent *e);
private:
int x;
void doPainting();

};
#endif // AMPEL_H
//***********************************************

(ampel.cpp)
//***********************************************
#include "ampel.h"
#include <QPainter>
//#include<mainwindow.h>

ampel::ampel(QWidget parent): QWidget(parent)
{
x=0;
}
//**********************************************
void ampel::paintEvent(QPaintEvent *e){
Q_UNUSED(e);

doPainting();

}
//***********************************************
void ampel::doPainting(){
QPainter dc(this);
QBrush pintada(Qt::green, Qt::SolidPattern);
pintada.setColor(Qt::red);
dc.setRenderHint(QPainter::Antialiasing,true);
dc.setPen(QPen(Qt::black,3, Qt::DashLine, Qt::RoundCap));
dc.setBrush(QBrush(pintada));// QBrush(Qt::green, Qt::SolidPattern)
dc.drawEllipse(x,x,25,25);
}
//*********************************************

(MainWindow.h)
//**********************************************
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "ampel.h"

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.cpp)
//*******************************************
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
this->setFixedSize(1024,768);
ampel a(this);
}

[mrjj]

@yczo said:
Hi
Code looks fine But

ampel a(this);

this is a local variable and it will be deleted !
as soon as constructor is fully run.
so here
ampel a(this);
} <<--- here a is deleted as it runs out of scope.

You must make it using new
ampel *a=new ampel (this);
ampel->resize(100,100); // set some size
ampel->show(); // ask it to be shown
setCentralWidget(ampel); // insert into mainwindows central widget.
Mainwindow is special as it has a central place holder widget.

[yczo]

Thank You very much, that works!

[mrjj]

@yczo
super.
If you want to make it follow size of mainwindow , you can insert
layout also. But mainwindow to fixed size so you seem not to need it :)