QLabel QPixmap change

[ludoQtCreator]

hello, sorry, I'm French so I'm talking with the translator, I want to change the image of a label based on a bool which is elsewhere in my program.
how can I do it???

THANKS

mainwindow.cpp

m_mainwindowThread.m_label = new QLabel(m_window);
    m_mainwindowThread.afficheLabelArret();

m_mainwindowThread.m_label = new QLabel(m_window);
    m_mainwindowThread.afficheLabelArret();

To copy to clipboard, switch view to plain text mode 

thread.h

QLabel *m_label;
 void afficheLabelArret();

QLabel *m_label;
 void afficheLabelArret();

To copy to clipboard, switch view to plain text mode 

thread.cpp

void Thread::afficheLabelArret()
{
if (m_threadGainable.labelModeFroid == true) {
	m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/froid.jpg")); 
else if (m_threadGainable.labelModeChauffage == true) {
	m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/chauffage.jpg"));
} else {   
m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/abigael.jpg"));
}
}
 
void Thread::run()
{
while (1) {
afficheLabelArret();
}
}

void Thread::afficheLabelArret()
{
if (m_threadGainable.labelModeFroid == true) {
	m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/froid.jpg")); 
else if (m_threadGainable.labelModeChauffage == true) {
	m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/chauffage.jpg"));
} else {   
m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/abigael.jpg"));
}
}

void Thread::run()
{
while (1) {
afficheLabelArret();
}
}

To copy to clipboard, switch view to plain text mode 

I have segfault randomly

[d_stranz]

You cannot directly change something in the GUI thread from a different thread. The reason you are getting a segfault is probably because the GUI thread and your "Thread" are not synchronized.

The correct way to do it is to emit a signal from your Thread that is connected to a slot in MainWindow.

class MainWindow : public QMainWindow
{
// ...
private slots:
  void onChangeLabel( int mode );
 
private:
  QLabel * m_label;
};
 
class Thread : public QThread
{
// ...
signals:
  void changeLabel(int mode );
};
 
MainWindow::MainWindow( QWidget * parent )
    : Qwidget( parent )
{
// ...
    connect( m_mainwindowThread, &Thread::changeLabel, this, &MainWindow::onChangeLabel );
}
 
void Thread::afficheLabelArret()
{
    if (m_threadGainable.labelModeFroid == true) {
	emit changeLabel( 0 ); 
    else if (m_threadGainable.labelModeChauffage == true) {
	emit changeLabel( 1 );
    } else {   
        emit changeLabel( 2 ); 
}
 
void MainWindow::onChangeLabel( int mode )
{
    switch( mode )
    {
        case 0:
            m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/froid.jpg")); 
            break;
 
        case 1:
            m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/chauffage.jpg"));
            break;
 
        default:
            m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/abigael.jpg"));
            break;
     }
}

class MainWindow : public QMainWindow
{
// ...
private slots:
  void onChangeLabel( int mode );

private:
  QLabel * m_label;
};

class Thread : public QThread
{
// ...
signals:
  void changeLabel(int mode );
};

MainWindow::MainWindow( QWidget * parent )
    : Qwidget( parent )
{
// ...
    connect( m_mainwindowThread, &Thread::changeLabel, this, &MainWindow::onChangeLabel );
}

void Thread::afficheLabelArret()
{
    if (m_threadGainable.labelModeFroid == true) {
	emit changeLabel( 0 ); 
    else if (m_threadGainable.labelModeChauffage == true) {
	emit changeLabel( 1 );
    } else {   
        emit changeLabel( 2 ); 
}

void MainWindow::onChangeLabel( int mode )
{
    switch( mode )
    {
        case 0:
            m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/froid.jpg")); 
            break;

        case 1:
            m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/chauffage.jpg"));
            break;

        default:
            m_label ->setPixmap(QPixmap("/home/ludo/Qt/test2/build/images/abigael.jpg"));
            break;
     }
}

To copy to clipboard, switch view to plain text mode 

The signal / slot mechanism will make sure that the inter-thread call is synchronized correctly.

[ludoQtCreator]

ok I'm going to try this tomorrow, do you have a coding organization for:
I want to manage a heating system with an rpi (raspberry) in c++! and use a graphical interface depending on the states of the GPIOs. go through temperatures.

if this speaks to you. Thank you in advance for giving me time to this project.

[d_stranz]

I want to manage a heating system with an rpi (raspberry) in c++! and use a graphical interface depending on the states of the GPIOs. go through temperature

I have not made such a project, but if you Google for "Raspberry Pi thermostat" you might find some good information.