Problem with comunication between widgets

[Lykurg]

you don't have to create a new button since the ui loader does that for you. You can access it as you do via ui->button. So just use that in your connect statement instead your temporary pointer:

connect(ui->button, SIGNAL/*...*/);

connect(ui->button, SIGNAL/*...*/);

To copy to clipboard, switch view to plain text mode 

And for simply displaying an image, you can use QLabel.

[laabor]

Thanks for help, but now I have new problem. I have added two QLabels, one on my QMainWindow widget and second on "paintArea" widget. Now what I want to do is change text on both of them, but from within "paintArea.h" class. I have tried quite a few things, but can't get this to work ?? A bit of code eplaining what i wabt to acomplish:

#include "paintarea.h"
 
paintarea::paintarea (QWidget *parent) :
    QWidget(parent)
{
 
    status = false ;
 
}
 
void paintarea::paintEvent(QPaintEvent *event)
{
    if(status)
    {
          QPainter painter(this);
          painter.drawPixmap(0,0,image);
 
 
     }
 
}
 
void paintarea::load_image(const QString &fileName)
{
 
 
    image.load(fileName);
 
    status = true ;
    update();
   // this->label->setText(image.width());  <---- that doesn't work, but this is example what i want to do, and I know I need first convert "image.width()" to string
   //ui->label_2->setText(image.height()); <---- also not woking
}

#include "paintarea.h"

paintarea::paintarea (QWidget *parent) :
    QWidget(parent)
{
  
    status = false ;
  
}

void paintarea::paintEvent(QPaintEvent *event)
{
    if(status)
    {
          QPainter painter(this);
          painter.drawPixmap(0,0,image);
        

     }

}

void paintarea::load_image(const QString &fileName)
{

   
    image.load(fileName);

    status = true ;
    update();
   // this->label->setText(image.width());  <---- that doesn't work, but this is example what i want to do, and I know I need first convert "image.width()" to string
   //ui->label_2->setText(image.height()); <---- also not woking
}

To copy to clipboard, switch view to plain text mode 

I know I need to declare somehow this "ui" but not sure exactly how, where ?

[Talei]

In paintarea, if image load suceed emit signal, connect that signal from mainwindows. Each time that signal is emited slot (in mainwindow) will fire up, something like this:
mainwindow:

connect( pArea, SIGNAL(mySIGNAL(int)), this, SLOT(updateLABEL(int)));

connect( pArea, SIGNAL(mySIGNAL(int)), this, SLOT(updateLABEL(int)));

To copy to clipboard, switch view to plain text mode 

paintarea must be on the stack i.e. paintarea *pArea; (include paintarea.h in mainWindow.h)

in mainWindow.cpp add

private slots:
void updateLABEL(int);

private slots:
void updateLABEL(int);

To copy to clipboard, switch view to plain text mode 

and:

void MainWindow::updateLABEL(int w)
{
//update label text
    this->ui->label->setText( QVariant(w).toString() );
}

void MainWindow::updateLABEL(int w)
{
//update label text
    this->ui->label->setText( QVariant(w).toString() );
}

To copy to clipboard, switch view to plain text mode 

int paintarea.cpp:

void paintarea::load_image(const QString &fileName)
{
 
 
    image.load(fileName);
 
    status = true ;
    update();
   // this->label->setText(image.width());  <---- that doesn't work, but this is example what i want to do, and I know I need first convert "image.width()" to string
   //ui->label_2->setText(image.height()); <---- also not woking
 
//emit signal if image load suceed
 emit mySIGNAL( image.width());
}

void paintarea::load_image(const QString &fileName)
{

   
    image.load(fileName);

    status = true ;
    update();
   // this->label->setText(image.width());  <---- that doesn't work, but this is example what i want to do, and I know I need first convert "image.width()" to string
   //ui->label_2->setText(image.height()); <---- also not woking

//emit signal if image load suceed
 emit mySIGNAL( image.width());
}

To copy to clipboard, switch view to plain text mode 

int paintarea.h:

signals:
    void mySIGNAL( int );

signals:
    void mySIGNAL( int );

To copy to clipboard, switch view to plain text mode 

Best luck

[axeljaeger]

Why does it not work?

[laabor]

I've made changes recommended by Talei, but still no luck all I can get is "Program finished unexpectedly, exited with code 0". There is no other errors in compilation. Any ideas why that's no working ? new code :
mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QtGui/QMainWindow>
#include <QPushButton>
#include <paintarea.h>
 
namespace Ui
{
    class mainwindow;
}
 
class mainwindow : public QMainWindow
{
    Q_OBJECT
 
public:
    mainwindow(QWidget *parent = 0);
    ~mainwindow();
 
 
 
private:
    Ui::mainwindow *ui;
    QPushButton *button;
    paintarea *parea;
 
 public slots:
     void send_signal();
 
 
  private slots:
     void updateLabel(int);
 
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtGui/QMainWindow>
#include <QPushButton>
#include <paintarea.h>

namespace Ui
{
    class mainwindow;
}

class mainwindow : public QMainWindow
{
    Q_OBJECT

public:
    mainwindow(QWidget *parent = 0);
    ~mainwindow();



private:
    Ui::mainwindow *ui;
    QPushButton *button;
    paintarea *parea;

 public slots:
     void send_signal();


  private slots:
     void updateLabel(int);

};

#endif // MAINWINDOW_H

To copy to clipboard, switch view to plain text mode 

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
mainwindow::mainwindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::mainwindow)
{
    ui->setupUi(this);
 
    button = new QPushButton;
    button = ui->button;
 
paintarea *parea;
 
     connect (button,SIGNAL (clicked()),this,SLOT (send_signal()));
     connect (parea, SIGNAL(mySignal(int)), this, SLOT(updateLabel(int)));
}
 
 
mainwindow::~mainwindow()
{
    delete ui;
}
 
 void mainwindow::send_signal()
 {
    ui->paint_space->load_image("/home/laabor/Pictures/test.jpeg");
 }
 
 void mainwindow::updateLabel(int w)
 {
     this->ui->label->setText(QVariant(w).toString());
 }

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

    button = new QPushButton;
    button = ui->button;

paintarea *parea;

     connect (button,SIGNAL (clicked()),this,SLOT (send_signal()));
     connect (parea, SIGNAL(mySignal(int)), this, SLOT(updateLabel(int)));
}


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

 void mainwindow::send_signal()
 {
    ui->paint_space->load_image("/home/laabor/Pictures/test.jpeg");
 }

 void mainwindow::updateLabel(int w)
 {
     this->ui->label->setText(QVariant(w).toString());
 }

To copy to clipboard, switch view to plain text mode 

paintarea.h

#ifndef PAINTAREA_H
#define PAINTAREA_H
 
#include <QWidget>
#include <QPainter>
#include <QPixmap>
#include <QLabel>
 
class paintarea : public QWidget
{
    Q_OBJECT
public:
    paintarea(QWidget *parent = 0);
    void load_image(const QString &fileName);
 
protected:
    void paintEvent(QPaintEvent *event);
    QPixmap image;
    QLabel label;
    bool status;
 
 signals:
    void mySignal(int);
};
 
#endif // PAINTAREA_H

#ifndef PAINTAREA_H
#define PAINTAREA_H

#include <QWidget>
#include <QPainter>
#include <QPixmap>
#include <QLabel>

class paintarea : public QWidget
{
    Q_OBJECT
public:
    paintarea(QWidget *parent = 0);
    void load_image(const QString &fileName);

protected:
    void paintEvent(QPaintEvent *event);
    QPixmap image;
    QLabel label;
    bool status;

 signals:
    void mySignal(int);
};

#endif // PAINTAREA_H

To copy to clipboard, switch view to plain text mode 

paintarea.cpp

#include "paintarea.h"
 
paintarea::paintarea (QWidget *parent) :
    QWidget(parent)
{
 
    status = false ;
 
 
}
 
void paintarea::paintEvent(QPaintEvent *event)
{
    if(status)
    {
          QPainter painter(this);
          painter.drawPixmap(0,0,image);
 
 
     }
 
}
 
void paintarea::load_image(const QString &fileName)
{
 
 
    image.load(fileName);
    status = true ;
    update();
 
   emit mySignal(image.width());
 
}

#include "paintarea.h"

paintarea::paintarea (QWidget *parent) :
    QWidget(parent)
{

    status = false ;


}

void paintarea::paintEvent(QPaintEvent *event)
{
    if(status)
    {
          QPainter painter(this);
          painter.drawPixmap(0,0,image);


     }

}

void paintarea::load_image(const QString &fileName)
{


    image.load(fileName);
    status = true ;
    update();

   emit mySignal(image.width());

}

To copy to clipboard, switch view to plain text mode 

[axeljaeger]

The program very like crashes in line 15 of mainwindow.cpp because of access to unitialized variable parea.

Also I do not understand what you want to do in line 9 & 10 of mainwindow.cpp.

[tbscope]

Some changes I would make to your code:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QtGui/QMainWindow>
#include <QPushButton>
#include <paintarea.h>
 
namespace Ui
{
    class mainwindow;
}
 
class mainwindow : public QMainWindow
{
    Q_OBJECT
 
public:
    mainwindow(QWidget *parent = 0);
    ~mainwindow();
 
 
 
private:
    Ui::mainwindow *ui;
    //QPushButton *button;  <---- Not necessary, ui->button is what you need.
    paintarea *parea;
 
 public slots:
     void send_signal();
 
 
  private slots:
     void updateLabel(int);
 
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QtGui/QMainWindow>
#include <QPushButton>
#include <paintarea.h>
 
namespace Ui
{
    class mainwindow;
}
 
class mainwindow : public QMainWindow
{
    Q_OBJECT
 
public:
    mainwindow(QWidget *parent = 0);
    ~mainwindow();
 
 
 
private:
    Ui::mainwindow *ui;
    //QPushButton *button;  <---- Not necessary, ui->button is what you need.
    paintarea *parea;
 
 public slots:
     void send_signal();
 
 
  private slots:
     void updateLabel(int);
 
};
 
#endif // MAINWINDOW_H

To copy to clipboard, switch view to plain text mode 

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
mainwindow::mainwindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::mainwindow)
{
    ui->setupUi(this);
 
    //button = new QPushButton;
    //button = ui->button;  <--- Not needed, it adds no functionality.
 
paintarea *parea;
 
//     connect (button,SIGNAL (clicked()),this,SLOT (send_signal()));
    connect(ui->button, SIGNAL(clicked()), this, SLOT(send_signal()));
     connect (parea, SIGNAL(mySignal(int)), this, SLOT(updateLabel(int)));
}
 
 
mainwindow::~mainwindow()
{
    delete ui;
}
 
 void mainwindow::send_signal()
 {
    ui->paint_space->load_image("/home/laabor/Pictures/test.jpeg");
 }
 
 void mainwindow::updateLabel(int w)
 {
     //this->ui->label->setText(QVariant(w).toString()); <--- Incorrect! You have to define a QVariant first, or use static functions.
    ui->label->setText(QString::number(w));
 }

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
mainwindow::mainwindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::mainwindow)
{
    ui->setupUi(this);
 
    //button = new QPushButton;
    //button = ui->button;  <--- Not needed, it adds no functionality.
 
paintarea *parea;
 
//     connect (button,SIGNAL (clicked()),this,SLOT (send_signal()));
    connect(ui->button, SIGNAL(clicked()), this, SLOT(send_signal()));
     connect (parea, SIGNAL(mySignal(int)), this, SLOT(updateLabel(int)));
}
 
 
mainwindow::~mainwindow()
{
    delete ui;
}
 
 void mainwindow::send_signal()
 {
    ui->paint_space->load_image("/home/laabor/Pictures/test.jpeg");
 }
 
 void mainwindow::updateLabel(int w)
 {
     //this->ui->label->setText(QVariant(w).toString()); <--- Incorrect! You have to define a QVariant first, or use static functions.
    ui->label->setText(QString::number(w));
 }

To copy to clipboard, switch view to plain text mode 

[laabor]

I'v found solution, it turned out to be very easy:

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
mainwindow::mainwindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::mainwindow)
{
    ui->setupUi(this);
 
 
 
 
    connect (ui->button,SIGNAL (clicked()),this,SLOT (send_signal()));
   connect (ui->paint_space, SIGNAL(mySignal(int)), this, SLOT(updateLabel(int)));
}
 
 
mainwindow::~mainwindow()
{
    delete ui;
}
 
 void mainwindow::send_signal()
 
 {
   QString fileName = QFileDialog::getOpenFileName(this);
   ui->paint_space->load_image(fileName);
 
 
 }
 
 void mainwindow::updateLabel(int w)
 {
     ui->label->setText("poszlo");
 }

#include "mainwindow.h"
#include "ui_mainwindow.h"

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




    connect (ui->button,SIGNAL (clicked()),this,SLOT (send_signal()));
   connect (ui->paint_space, SIGNAL(mySignal(int)), this, SLOT(updateLabel(int)));
}


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

 void mainwindow::send_signal()

 {
   QString fileName = QFileDialog::getOpenFileName(this);
   ui->paint_space->load_image(fileName);


 }

 void mainwindow::updateLabel(int w)
 {
     ui->label->setText("poszlo");
 }

To copy to clipboard, switch view to plain text mode