Erittäin yksinkertaiset liikennevalot Qt-tilakoneena

Tee käyttöliittymä, jossa on painike nimeltä  switchState ja kolme QLabel-elementtiä nimiltään red, yellow ja green. mainwindow.cpp näyttää seuraavalta:

#include "mainwindow.h"

#include "ui_mainwindow.h"

#include <QStateMachine>

#include <QFinalState>

MainWindow::MainWindow(QWidget *parent) :

 QMainWindow(parent),

 ui(new Ui::MainWindow)

{

 ui->setupUi(this);

 QStateMachine *trafficLights=new QStateMachine(this);

 QState *red=new QState(trafficLights);

 QState *yellow=new QState(trafficLights);

 QState *green=new QState(trafficLights);

 trafficLights->addState(red);

 trafficLights->addState(yellow);

 trafficLights->addState(green);

 trafficLights->setInitialState(red);

 trafficLights->start();

 QString grey="background-color:grey";

 red->assignProperty(ui->red,"styleSheet","background-color:red");

 yellow->assignProperty(ui->yellow,"styleSheet","background-color:yellow");

 green->assignProperty(ui->green,"styleSheet","background-color:green");

 // set all other lights to grey

 yellow->assignProperty(ui->red,"styleSheet",grey);

 green->assignProperty(ui->red,"styleSheet",grey);

 red->assignProperty(ui->green,"styleSheet",grey);

 yellow->assignProperty(ui->green,"styleSheet",grey);

 red->assignProperty(ui->yellow,"styleSheet",grey);

 green->assignProperty(ui->yellow,"styleSheet",grey);

 red->addTransition(ui->switchState,SIGNAL(clicked()),yellow);

 yellow->addTransition(ui->switchState,SIGNAL(clicked()),green);

 green->addTransition(ui->switchState,SIGNAL(clicked()),red);

}

MainWindow::~MainWindow()

{

 delete ui;

}