How to declare a function for click button event

[prajnaranjan.das]

//mainwindow.h

class ButtonLayout : public QWidget
 {
     Q_OBJECT
 
 public:
     ButtonLayout(QWidget *parent = 0);
 
 public slots:
    void openImage();
 
 };
 
 class ImageViewer : public QWidget
 {
     Q_OBJECT
 
 public:
     ImageViewer(QWidget *parent = 0);
 };

class ButtonLayout : public QWidget
 {
     Q_OBJECT

 public:
     ButtonLayout(QWidget *parent = 0);

 public slots:
    void openImage();

 };

 class ImageViewer : public QWidget
 {
     Q_OBJECT

 public:
     ImageViewer(QWidget *parent = 0);
 };

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//mainwindow.cpp

ButtonLayout::ButtonLayout(QWidget *parent)
     : QWidget(parent)
 {
     QPushButton *btn1 = new QPushButton("IMAGE");
 
     connect(btn1,SIGNAL(clicked()),this,SLOT(openImage()));
 
     QVBoxLayout *layout = new QVBoxLayout;
     layout->addWidget(btn1);
     setLayout(layout);
 }
 
 ImageViewer::ImageViewer(QWidget *parent):QWidget(parent)
 {
     QLabel  *lblImage = new QLabel;
     QPixmap pixmap(QPixmap::fromImage(QImage(":/images/Resource/photo.JPG")));
     lblImage->setPixmap(pixmap);
 
 
     QVBoxLayout *layout = new QVBoxLayout;
     layout->addWidget(lblImage);
     setLayout(layout);
 }
 
 void ButtonLayout::openImage()
 {
     ImageViewer *viewer = new ImageViewer;
     viewer->show();
 }

ButtonLayout::ButtonLayout(QWidget *parent)
     : QWidget(parent)
 {
     QPushButton *btn1 = new QPushButton("IMAGE");

     connect(btn1,SIGNAL(clicked()),this,SLOT(openImage()));

     QVBoxLayout *layout = new QVBoxLayout;
     layout->addWidget(btn1);
     setLayout(layout);
 }

 ImageViewer::ImageViewer(QWidget *parent):QWidget(parent)
 {
     QLabel  *lblImage = new QLabel;
     QPixmap pixmap(QPixmap::fromImage(QImage(":/images/Resource/photo.JPG")));
     lblImage->setPixmap(pixmap);


     QVBoxLayout *layout = new QVBoxLayout;
     layout->addWidget(lblImage);
     setLayout(layout);
 }

 void ButtonLayout::openImage()
 {
     ImageViewer *viewer = new ImageViewer;
     viewer->show();
 }

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I have declared two classes for it to show a image when I press the Image button...Can I declare these things in one class...