Signals_and_Slots_on_QThread_wit_sired_class

**BACKER** · 2011-10-03, 18:36

goodday everyone
I have a problem with signals and slots when using a shared file called 'settings'.
I'm unable to emit a signal from settings if it's been been called from a sub thread.
To demonstrate problem I wrote this little program:

CODE

Signals_and_Slots_on_QThread_wit_sired_class.PRO

Code:

QT       += core gui

TARGET = Signals_and_Slots_on_QThread_wit_sired_class
TEMPLATE = app

SOURCES += main.cpp\
        widget.cpp \
    thread.cpp \
    settings.cpp

HEADERS  += widget.h \
    thread.h \
    settings.h

main.cpp

Code:

#include <QtGui/QApplication>
#include "widget.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();

    return a.exec();
}

widget.h

Code:

#ifndef WIDGET_H
#define WIDGET_H
#include "settings.h"
#include "thread.h"
#include <QtGui/QWidget>
#include <QLineEdit>
#include <QTextBrowser>
#include <QGridLayout>

class Widget : public QWidget
{
    Q_OBJECT

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

public slots:
    void print(QString,int,int,int);//text, red, green, blue
    void print_append(QString,int,int,int);//text, red, green, blue

private:
    Thread thread;
    settings Settings;
    QLineEdit *lineEdit;
    QTextBrowser *textBrowser_info;

private slots:
    void readSettings();
};
#endif // WIDGET_H

widget.cpp

Code:

#include "widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    lineEdit = new QLineEdit;
    textBrowser_info = new QTextBrowser;
    QGridLayout *layout = new QGridLayout;
    layout->addWidget(lineEdit, 0, 0);
    layout->addWidget(textBrowser_info, 1, 0);
    setLayout(layout);
    /* Settings */
        connect(&Settings, SIGNAL(info(QString,int,int,int)),
                this, SLOT(print(QString,int,int,int)),
                Qt::AutoConnection);
        connect(&Settings, SIGNAL(info_append(QString,int,int,int)),
                this, SLOT(print_append(QString,int,int,int)),
                Qt::AutoConnection);
    /* thread */
        connect(&thread, SIGNAL(info(QString,int,int,int)),
                this, SLOT(print(QString,int,int,int)),
                Qt::AutoConnection);
        connect(&thread, SIGNAL(info_append(QString,int,int,int)),
                this, SLOT(print_append(QString,int,int,int)),
                Qt::AutoConnection);
        /* einde connect */
                    print("test start",100, 100, 100);

                    readSettings();
                    print("test done",100, 100, 100);
                    thread.start_uitlezen();
}

Widget::~Widget() {}

void Widget::print(QString temp,int red,int green,int blue)
{
    textBrowser_info->setTextColor(QColor(red, green, blue, 255));
    textBrowser_info->append(temp);
}

void Widget::print_append(QString temp,int red,int green,int blue)
{
    textBrowser_info->setTextColor(QColor(red, green, blue, 255));
    textBrowser_info->insertPlainText(temp);
}

void Widget::readSettings() {
    lineEdit->setText(Settings.dir_uitlezen());
}

settings.h

Code:

#ifndef SETTINGS_H
#define SETTINGS_H

#include <QObject>
#include <QSettings>
const QString file="settings.ini";

class settings : public QObject
{
    Q_OBJECT
public:
    explicit settings(QObject *parent = 0);
    QString readSettings(QString beginGroup, QString value, QString var);

    // readSettings
    QString dir_uitlezen();

signals:
    void info(QString,int,int,int);//text, red, green, blue
    void info_append(QString,int,int,int);//text, red, green, blue
};

#endif // SETTINGS_H

settings.cpp

Code:

#include "settings.h"
settings::settings(QObject *parent) :
    QObject(parent)
{}

QString settings::readSettings(QString beginGroup, QString value, QString var)
{
    QSettings settings(file,QSettings::IniFormat);
    QString temp;
    settings.beginGroup(beginGroup);
    temp=settings.value(value,var).toString();
    settings.endGroup();
    emit info("-settings R- ["+beginGroup+"] "+value+" ="+temp,0,100,0);
    return temp;
}

QString settings::dir_uitlezen()
{
#ifdef Q_OS_LINUX
    return readSettings("mapen_linux","dir_uitlezen","/home/user/Documenten/Uitlezingen/");
#endif
#ifdef Q_WS_WIN
/* #elif Q_WS_WIN  "error" */
    return readSettings("mapen_windows","dir_uitlezen","C:/Documents/Uitlezingen");
#endif
}

thread.h

Code:

#ifndef THREAD_H
#define THREAD_H

#include <QObject>
#include <QThread>
#include "settings.h"

class Thread : public QThread
{
    Q_OBJECT
public:
    explicit Thread(QThread *parent = 0);
    ~Thread();

protected:
    void run();

signals:
    void info(QString,int,int,int);//text, red, green, blue
    void info_append(QString,int,int,int);//text, red, green, blue

public slots:
    void start_uitlezen();

private:
    settings Settings;
    QString dir_uitlezen;
    QString out_file;
    void readSettings();
};
#endif // THREAD_H

thread.cpp

Code:

#include "thread.h"

Thread::Thread(QThread *parent) :
    QThread(parent)
{
    moveToThread(this);
}

Thread::~Thread()
{
    wait();
}

void Thread::run()
{
    exec();
}

/* => settings.h */
void Thread::readSettings()
{
    dir_uitlezen=Settings.dir_uitlezen();
}

void Thread::start_uitlezen()
{
    emit info("start dir_uitlezen",0,0,100);
    readSettings();
    emit info("waarom geen '-settings R-' getoond?",255,0,0);
    emit info("done dir_uitlezen",0,0,100);
    this->exit(0);
}

the first time it calls settings it displays settings R and a folder.
the second time it does not display this.
this has been called from what I believe the thread while the same thread is able to broadcast text.
Why is this? Did I forget something?

sincerely
BACKER

**gnuton** · 2011-10-11, 17:14

I'm unable to emit a signal from settings if it's been been called from a sub thread.

I think signal is emitted by settings in the thread, but you are not listening for it!

**BACKER** · 2011-10-15, 09:07

yes, in debug its clearly visible,
but

Code:

        connect(&Settings, SIGNAL(info(QString,int,int,int)),
                this, SLOT(print(QString,int,int,int)),
                Qt::AutoConnection);

not listening
and

Code:

connect(&thread, SIGNAL(info(QString,int,int,int)),
                this, SLOT(print(QString,int,int,int)),
                Qt::AutoConnection);

not listening

@doc.qt.nokia.com
A class which emits a signal neither knows nor cares which slots receive the signal.

Signal OK
Slot OK
Meta-Object problem?

I forget what?

sincerely
BACKER

**BACKER** · 2012-06-19, 21:10

fix add => Qt::QueuedConnection

Signals_and_Slots_on_QThread_wit_sired_class.PRO

Code:

QT       += core gui

TARGET = Signals_and_Slots_on_QThread_wit_sired_class
TEMPLATE = app

SOURCES += main.cpp\
        widget.cpp \
    thread.cpp \
    settings.cpp

HEADERS  += widget.h \
    thread.h \
    settings.h

main.cpp

Code:

#include <QtGui/QApplication>
#include "widget.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();

    return a.exec();
}

widget.h

Code:

#ifndef WIDGET_H
#define WIDGET_H
#include "settings.h"
#include "thread.h"
#include <QtGui/QWidget>
#include <QLineEdit>
#include <QTextBrowser>
#include <QGridLayout>

class Widget : public QWidget
{
    Q_OBJECT

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

public slots:
    void print(QString,int,int,int);//text, red, green, blue
    void print_append(QString,int,int,int);//text, red, green, blue

private:
    Thread thread;
    settings Settings;
    QLineEdit *lineEdit;
    QTextBrowser *textBrowser_info;

private slots:
    void readSettings();
};
#endif // WIDGET_H

widget.cpp

Code:

#include "widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    lineEdit = new QLineEdit;
    textBrowser_info = new QTextBrowser;
    QGridLayout *layout = new QGridLayout;
    layout->addWidget(lineEdit, 0, 0);
    layout->addWidget(textBrowser_info, 1, 0);
    setLayout(layout);
    /* Settings */
    connect(&Settings, SIGNAL(info(QString,int,int,int)),
            this, SLOT(print(QString,int,int,int)),
            Qt::AutoConnection);
    connect(&Settings, SIGNAL(info_append(QString,int,int,int)),
            this, SLOT(print_append(QString,int,int,int)),
            Qt::AutoConnection);

    /*-!! fix add => Qt::QueuedConnection <= !!-*/
    connect(&Settings, SIGNAL(info(QString,int,int,int)),
            this, SLOT(print(QString,int,int,int)),
            Qt::QueuedConnection);
    connect(&Settings, SIGNAL(info_append(QString,int,int,int)),
            this, SLOT(print_append(QString,int,int,int)),
            Qt::QueuedConnection);
    /*-!! end fix !!-*/

    /* thread */
        connect(&thread, SIGNAL(info(QString,int,int,int)),
                this, SLOT(print(QString,int,int,int)),
                Qt::AutoConnection);
        connect(&thread, SIGNAL(info_append(QString,int,int,int)),
                this, SLOT(print_append(QString,int,int,int)),
                Qt::AutoConnection);
        /* einde connect */
                    print("test start",100, 100, 100);

                    readSettings();
                    print("test done",100, 100, 100);

                    thread.moveToThread(&thread);
                    thread.start();
                    thread.start_uitlezen();
}

Widget::~Widget() {
    thread.quit();
}

void Widget::print(QString temp,int red,int green,int blue)
{
    textBrowser_info->setTextColor(QColor(red, green, blue, 255));
    textBrowser_info->append(temp);
}

void Widget::print_append(QString temp,int red,int green,int blue)
{
    textBrowser_info->setTextColor(QColor(red, green, blue, 255));
    textBrowser_info->insertPlainText(temp);
}

void Widget::readSettings() {
    lineEdit->setText(Settings.dir_uitlezen());
}

settings.h

Code:

#ifndef SETTINGS_H
#define SETTINGS_H

#include <QObject>
#include <QSettings>
const QString file="settings.ini";

class settings : public QObject
{
    Q_OBJECT
public:
    explicit settings(QObject *parent = 0);
    QString readSettings(QString beginGroup, QString value, QString var);

    // readSettings
    QString dir_uitlezen();

signals:
    void info(QString,int,int,int);//text, red, green, blue
    void info_append(QString,int,int,int);//text, red, green, blue
};

#endif // SETTINGS_H

settings.cpp

Code:

#include "settings.h"
settings::settings(QObject *parent) :
    QObject(parent)
{}

QString settings::readSettings(QString beginGroup, QString value, QString var)
{
    QSettings settings(file,QSettings::IniFormat);
    QString temp;
    settings.beginGroup(beginGroup);
    temp=settings.value(value,var).toString();
    settings.endGroup();
    emit info("-settings R- ["+beginGroup+"] "+value+" ="+temp,0,100,0);
    return temp;
}

QString settings::dir_uitlezen()
{
#ifdef Q_OS_LINUX
    return readSettings("mapen_linux","dir_uitlezen","/home/user/Documenten/Uitlezingen/");
#endif
#ifdef Q_WS_WIN
/* #elif Q_WS_WIN  "error" */
    return readSettings("mapen_windows","dir_uitlezen","C:/Documents/Uitlezingen");
#endif
}

thread.h

Code:

#ifndef THREAD_H
#define THREAD_H

#include <QObject>
#include <QThread>
#include "settings.h"

class Thread : public QThread
{
    Q_OBJECT
public:
    explicit Thread(QThread *parent = 0);
    ~Thread();

protected:
    void run();

signals:
    void info(QString,int,int,int);//text, red, green, blue
    void info_append(QString,int,int,int);//text, red, green, blue

public slots:
    void start_uitlezen();

private:
    settings Settings;
    QString dir_uitlezen;
    QString out_file;
    int exit;
    void readSettings();
};
#endif // THREAD_H

thread.cpp

Code:

#include "thread.h"

Thread::Thread(QThread *parent) :
    QThread(parent)
{exit=1;}

Thread::~Thread()
{
    wait();
}

void Thread::run()
{
    while (exit>0) {}
    exec();
}

/* => settings.h */
void Thread::readSettings()
{
    dir_uitlezen=Settings.dir_uitlezen();
}

void Thread::start_uitlezen()
{
    emit info("start dir_uitlezen",0,0,100);
    readSettings();
    emit info("waarom geen '-settings R-' getoond?",255,0,0);
    emit info("done dir_uitlezen",0,0,100);
    emit info("nu wel ",0,100,100);
    exit=0;
}

sincerely
BACKER

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