Qt Reference Documentation

# main.cpp Example File

statemachine/trafficlight/main.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
     ** All rights reserved.
     ** Contact: Nokia Corporation (qt-info@nokia.com)
     **
     ** This file is part of the QtCore module of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
     **     notice, this list of conditions and the following disclaimer.
     **   * Redistributions in binary form must reproduce the above copyright
     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
     **     distribution.
     **   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
     **     the names of its contributors may be used to endorse or promote
     **     products derived from this software without specific prior written
     **     permission.
     **
     ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
     ** $QT_END_LICENSE$
     **
     ****************************************************************************/

     #include <QtGui>

     class LightWidget : public QWidget
     {
         Q_OBJECT
         Q_PROPERTY(bool on READ isOn WRITE setOn)
     public:
         LightWidget(const QColor &color, QWidget *parent = 0)
             : QWidget(parent), m_color(color), m_on(false) {}

         bool isOn() const
             { return m_on; }
         void setOn(bool on)
         {
             if (on == m_on)
                 return;
             m_on = on;
             update();
         }

     public slots:
         void turnOff() { setOn(false); }
         void turnOn() { setOn(true); }

     protected:
         virtual void paintEvent(QPaintEvent *)
         {
             if (!m_on)
                 return;
             QPainter painter(this);
             painter.setRenderHint(QPainter::Antialiasing);
             painter.setBrush(m_color);
             painter.drawEllipse(0, 0, width(), height());
         }

     private:
         QColor m_color;
         bool m_on;
     };

     class TrafficLightWidget : public QWidget
     {
     public:
         TrafficLightWidget(QWidget *parent = 0)
             : QWidget(parent)
         {
             QVBoxLayout *vbox = new QVBoxLayout(this);
             m_red = new LightWidget(Qt::red);
             vbox->addWidget(m_red);
             m_yellow = new LightWidget(Qt::yellow);
             vbox->addWidget(m_yellow);
             m_green = new LightWidget(Qt::green);
             vbox->addWidget(m_green);
             QPalette pal = palette();
             pal.setColor(QPalette::Background, Qt::black);
             setPalette(pal);
             setAutoFillBackground(true);
         }

         LightWidget *redLight() const
             { return m_red; }
         LightWidget *yellowLight() const
             { return m_yellow; }
         LightWidget *greenLight() const
             { return m_green; }

     private:
         LightWidget *m_red;
         LightWidget *m_yellow;
         LightWidget *m_green;
     };

     QState *createLightState(LightWidget *light, int duration, QState *parent = 0)
     {
         QState *lightState = new QState(parent);
         QTimer *timer = new QTimer(lightState);
         timer->setInterval(duration);
         timer->setSingleShot(true);
         QState *timing = new QState(lightState);
         QObject::connect(timing, SIGNAL(entered()), light, SLOT(turnOn()));
         QObject::connect(timing, SIGNAL(entered()), timer, SLOT(start()));
         QObject::connect(timing, SIGNAL(exited()), light, SLOT(turnOff()));
         QFinalState *done = new QFinalState(lightState);
         timing->addTransition(timer, SIGNAL(timeout()), done);
         lightState->setInitialState(timing);
         return lightState;
     }

     class TrafficLight : public QWidget
     {
     public:
         TrafficLight(QWidget *parent = 0)
             : QWidget(parent)
         {
             QVBoxLayout *vbox = new QVBoxLayout(this);
             TrafficLightWidget *widget = new TrafficLightWidget();
             vbox->addWidget(widget);
             vbox->setMargin(0);

             QStateMachine *machine = new QStateMachine(this);
             QState *redGoingYellow = createLightState(widget->redLight(), 3000);
             redGoingYellow->setObjectName("redGoingYellow");
             QState *yellowGoingGreen = createLightState(widget->yellowLight(), 1000);
             yellowGoingGreen->setObjectName("yellowGoingGreen");
             redGoingYellow->addTransition(redGoingYellow, SIGNAL(finished()), yellowGoingGreen);
             QState *greenGoingYellow = createLightState(widget->greenLight(), 3000);
             greenGoingYellow->setObjectName("greenGoingYellow");
             yellowGoingGreen->addTransition(yellowGoingGreen, SIGNAL(finished()), greenGoingYellow);
             QState *yellowGoingRed = createLightState(widget->yellowLight(), 1000);
             yellowGoingRed->setObjectName("yellowGoingRed");
             greenGoingYellow->addTransition(greenGoingYellow, SIGNAL(finished()), yellowGoingRed);
             yellowGoingRed->addTransition(yellowGoingRed, SIGNAL(finished()), redGoingYellow);

             machine->addState(redGoingYellow);
             machine->addState(yellowGoingGreen);
             machine->addState(greenGoingYellow);
             machine->addState(yellowGoingRed);
             machine->setInitialState(redGoingYellow);
             machine->start();
         }
     };

     int main(int argc, char **argv)
     {
         QApplication app(argc, argv);

         TrafficLight widget;
         widget.resize(110, 300);
         widget.show();

         return app.exec();
     }

     #include "main.moc"