QT4

#ifndef HALLOWELTFENSTER6_H
#define HALLOWELTFENSTER6_H

#include <QMainWindow>

namespace Ui {
class HalloWeltFenster6;
}

class HalloWeltFenster6 : public QMainWindow
{
    Q_OBJECT

public:
    explicit HalloWeltFenster6(QWidget *parent = 0);
    ~HalloWeltFenster6();
    void test();

public slots:
    void update();


private:
    Ui::HalloWeltFenster6 *ui;
};

#endif // HALLOWELTFENSTER6_H
------------------------------------------------------------------
#include "halloweltfenster6.h"
#include "ui_halloweltfenster6.h"

HalloWeltFenster6::HalloWeltFenster6(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::HalloWeltFenster6)
{
    ui->setupUi(this);
}

HalloWeltFenster6::~HalloWeltFenster6()
{
    delete ui;
}

void HalloWeltFenster6::update()
{
    ui->label->setText("Test");
}