QTextEdit promoted to Construct a Console Window

first of all I am a beginner with Qt and C++ and this is my first post here so I am open to improvement suggestions, so for you guys this Question might be stupid. Nevertheless I hope someone can help me fix my problem. I try to construct a promoted QTextEdit Console widget for my Gui in which i redirect all std::cout. For the redirection i mostly followed this tutorial:

http://ift.tt/2vege0b

My Code looks like this: myConsoleStream.cpp:

#include "myconsolestream.h"    

myConsoleStream::myConsoleStream(std::ostream &stream, QTextEdit* text_edit,QWidget *parent)
    :std::basic_streambuf<char>()
    ,m_stream(stream)
    ,myConsole(parent)

{
    this->log_window = text_edit;
    this->m_old_buf = stream.rdbuf();

    stream.rdbuf(this);


}

myConsoleStream::~myConsoleStream()
{
    this->m_stream.rdbuf(this->m_old_buf);
}

void myConsoleStream::registerMyConsoleMessageHandler()
{
    qInstallMessageHandler(myConsoleMessageHandler);
}


void myConsoleStream::myConsoleMessageHandler(QtMsgType, const QMessageLogContext &, const QString &msg)
{
    std::cout << msg.toStdString().c_str();
}




std::streamsize myConsoleStream::xsputn(const char *p, std::streamsize n)
{
    QString str(p);
    if(str.contains("\n"))
    {
        QStringList strSplitted = str.split("\n");

        this->log_window->moveCursor (QTextCursor::End);
        this->log_window->insertPlainText (strSplitted.at(0)); //Index 0 immer noch auf der alten Zeile

        for(int i = 1; i < strSplitted.size(); i++)
        {
            this->log_window->append(strSplitted.at(i));
        }
    }
    else
    {
        log_window->moveCursor (QTextCursor::End);
        log_window->insertPlainText (str);
    }
    return n;
}

myConsoleStream.h:

#ifndef Q_DEBUGSTREAM_H
#define Q_DEBUGSTREAM_H


#include <iostream>
#include <streambuf>
#include <string>
#include <QObject>
#include <QWidget>
#include "QTextEdit"
#include <QApplication>
#include "myconsole.h"


class myConsoleStream :  public std::basic_streambuf<char>,  myConsole
{

public:
    myConsoleStream(std::ostream &stream, QTextEdit* text_edit, QWidget *parent);


    virtual ~myConsoleStream();
    static void registerMyConsoleMessageHandler();





private:

    static void myConsoleMessageHandler(QtMsgType, const QMessageLogContext &, const QString &msg);

protected:


    // Diese Funktion wird aufgerufen wenn std::endl im Stream erscheint
    virtual int_type overflow(int_type v)
        {
            if (v == '\n')
            {
                log_window->append("");
            }
            return v;
        }

    virtual std::streamsize xsputn(const char *p, std::streamsize n);

private:

    std::ostream &m_stream;
    std::streambuf *m_old_buf;
    QTextEdit* log_window;

};
#endif // Q_DEBUGSTREAM_H

I tried to make this class a subclass of an additional class to which I promoted the QTextEdit to.Which looks like this:

#include "myconsole.h"


myConsole::myConsole(QWidget *parent)
    :QTextEdit(parent)
{

}

myConsole::~myConsole()
{


}

Last but not least my Mainwindow Class looks like this:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QBoxLayout>
#include <QTimer>
#include "myconsolestream.h"


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

    new myConsoleStream(std::cout, this->ui->Console,this);//Redirect Console output to QTextEdit
    myConsoleStream::registerMyConsoleMessageHandler(); //Redirect qDebug() output to QTextEdit


    std::cout << "Hallo" << std::endl;
}

MainWindow::~MainWindow()
{
    delete ui;


}

Now to my Problem:

If I execute this there appears a second QTextEdit in the Left upperhand corner of my Mainwindow, which I dont want to have there. And I cant figure out why this is appearing or where this is created ??

Btw I am using qt5.5 and QtCreator for that matter.