Access to UI elements from another class c++

[nasil122002]

Hello,

I have a problem with accessing to ui elements from another class(with instance). I have a second QMainWindow in my application, I can access in secondWindow.cxx class all ui elements but not in read.cxx class. My code looks like following. Where is my mistake? Thank you for your help.

//-------------------------------secondWindow.h------------------------------------
    #ifndef __secondWindow_h
    #define __secondWindow_h
 
    #include "ui_secondwindow.h"
 
    class secondWindow : public QMainWindow
    {
        friend class read;
        igstkStandardClassBasicTraitsMacro(secondWindow, QMainWindow);
        Q_OBJECT
 
    public:
        igstkStateMachineMacro();
 
        secondWindow();
        virtual ~secondWindow();
        void createSignalAndSlots();
 
    public slots:
        void secondWindowTest();
 
    protected:
 
    private:
        Ui::secondMainWindow m_secondWindowUI;
    };
    #endif

//-------------------------------secondWindow.h------------------------------------
    #ifndef __secondWindow_h
    #define __secondWindow_h

    #include "ui_secondwindow.h"

    class secondWindow : public QMainWindow
    {
        friend class read;
        igstkStandardClassBasicTraitsMacro(secondWindow, QMainWindow);
        Q_OBJECT

    public:
        igstkStateMachineMacro();

        secondWindow();
        virtual ~secondWindow();
        void createSignalAndSlots();

    public slots:
        void secondWindowTest();

    protected:

    private:
        Ui::secondMainWindow m_secondWindowUI;
    };
    #endif

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//-------------------------------secondWindow.cxx------------------------------------
    #include "secondWindow.moc"
    #include "secondWindow.h"
    #include "read.h"
 
    secondWindow::secondWindow() :m_StateMachine(this)
    {
        m_secondWindowUI.setupUi(this);
        createSignalAndSlots();
    }
 
    void secondWindow::createSignalAndSlots()
    {
        connect(m_secondWindowUI.pushButton1, SIGNAL(clicked()),this, SLOT(secondWindowTest()));
 
        connect(m_secondWindowUI.pushButton2, SIGNAL(clicked()), read::instance(), SLOT(readTest()));
    }
 
    void secondWindow::secondWindowTest()
    {
        m_secondWindowUI.pushButton1->setEnabled(true); //OK
    }
 
    secondWindow::~secondWindow(){}

//-------------------------------secondWindow.cxx------------------------------------
    #include "secondWindow.moc"
    #include "secondWindow.h"
    #include "read.h"

    secondWindow::secondWindow() :m_StateMachine(this)
    {
        m_secondWindowUI.setupUi(this);
        createSignalAndSlots();
    }

    void secondWindow::createSignalAndSlots()
    {
        connect(m_secondWindowUI.pushButton1, SIGNAL(clicked()),this, SLOT(secondWindowTest()));

        connect(m_secondWindowUI.pushButton2, SIGNAL(clicked()), read::instance(), SLOT(readTest()));
    }

    void secondWindow::secondWindowTest()
    {
        m_secondWindowUI.pushButton1->setEnabled(true); //OK
    }

    secondWindow::~secondWindow(){}

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//---------------------------------read.h--------------------------------------
    #pragma once
 
    #include "secondWindow.h"
 
    class read : public QObject
    {
        Q_OBJECT
 
    public:
        static read *instance();
        read();
        virtual ~read() {}
 
    public slots:
        void readTest();
 
    protected:
        secondWindow	*m_readUI;
        static read 	*m_read;
 
    private:
    };

//---------------------------------read.h--------------------------------------
    #pragma once

    #include "secondWindow.h"

    class read : public QObject
    {
        Q_OBJECT

    public:
        static read *instance();
        read();
        virtual ~read() {}

    public slots:
        void readTest();

    protected:
        secondWindow	*m_readUI;
        static read 	*m_read;

    private:
    };

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//---------------------------------read.cxx--------------------------------------
    #include <read.moc>
    #include "secondWindow.h"
    #include "read.h"
 
    read *read::m_read= NULL;
 
    read::read()
    {
        m_readUI = dynamic_cast<secondWindow*>( QApplication::instance() );
    }
 
    read *read::instance()
    {
        if(m_read == NULL)
        m_read = new read();
 
        return m_read;
    }
 
    void read::readTest()
    {
        m_readUI->m_secondWindowUI.qlabelTest->setText("test"); //segmentation fault
    }

//---------------------------------read.cxx--------------------------------------
    #include <read.moc>
    #include "secondWindow.h"
    #include "read.h"

    read *read::m_read= NULL;

    read::read()
    {
        m_readUI = dynamic_cast<secondWindow*>( QApplication::instance() );
    }

    read *read::instance()
    {
        if(m_read == NULL)
        m_read = new read();
        
        return m_read;
    }

    void read::readTest()
    {
        m_readUI->m_secondWindowUI.qlabelTest->setText("test"); //segmentation fault
    }

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