c++ - Transitioning between menu screens with QStateMachine -

i considering transitioning between menu screens in game using qstatemachine. however, i'm unsure how kick off code (e.g. show() qwidget) upon transition between states occurring. can quite plain old signals (see commented out code), figure fancy animation upon switching screens using transitions.

here's code:

edit: updated per koying's suggestion.

applicationwindow.h:

#include <qtgui> #include <qstatemachine>  #include "mainmenu.h" #include "loadgamemenu.h"  class applicationwindow : public qmainwindow {     q_object public:     applicationwindow(); private slots:     void mainmenubuttonclicked();     void loadgamemenubuttonclicked(); private:     mainmenu* mainmenu;     loadgamemenu* loadgamemenu;      qstatemachine statemachine;      qstackedwidget* stack; }; 

applicationwindow.cpp:

applicationwindow::applicationwindow() {     resize(800, 600);      stack = new qstackedwidget(this);      mainmenu = new mainmenu();     setcentralwidget(mainmenu);     loadgamemenu = new loadgamemenu();      qstate* mainmenustate = new qstate();     qstate* loadgamemenustate = new qstate();      qabstracttransition* loadtransition = mainmenustate->addtransition(         mainmenu, signal(loadgameclicked()), loadgamemenustate);     connect(loadtransition, signal(triggered()), this, slot(loadgamemenubuttonclicked()));      qabstracttransition* mainmenutransition = loadgamemenustate->addtransition(         loadgamemenu, signal(backtomainmenuclicked()), mainmenustate);     connect(mainmenutransition, signal(triggered()), this, slot(mainmenubuttonclicked()));      statemachine.addstate(mainmenustate);     statemachine.addstate(loadgamemenustate);      statemachine.setinitialstate(mainmenustate);     statemachine.start(); }  void applicationwindow::mainmenubuttonclicked() {     setcentralwidget(mainmenu); }  void applicationwindow::loadgamemenubuttonclicked() {     setcentralwidget(loadgamemenu); } 

loadgamemenu.h:

#include <qtgui>  class loadgamemenu : public qwidget {     q_object public:     loadgamemenu(); signals:     void backtomainmenuclicked(); private:     qpushbutton* loadgamebutton;     qpushbutton* backtomainmenubutton; }; 

loadgamemenu.cpp:

#include "loadgamemenu.h"  loadgamemenu::loadgamemenu() {     loadgamebutton = new qpushbutton(tr("load"));     backtomainmenubutton = new qpushbutton(tr("main menu"));      qobject::connect(backtomainmenubutton, signal(clicked()),         this, signal(backtomainmenuclicked()));      qvboxlayout* layout = new qvboxlayout();     layout->addwidget(loadgamebutton);     layout->addwidget(backtomainmenubutton);     layout->setcontentsmargins(300, 400, 300, 200);     setlayout(layout); } 

mainmenu.h:

#include <qtgui>  class mainmenu : public qwidget {     q_object public:     mainmenu(); signals:     void newgameclicked();     void loadgameclicked(); private slots:     void exit(); private:     qpushbutton* newgamebutton;     qpushbutton* loadgamebutton;     qpushbutton* exitgamebutton;      qmenu* filemenu; }; 

mainmenu.cpp:

#include "mainmenu.h"  mainmenu::mainmenu() {     newgamebutton = new qpushbutton(tr("new game"), this);     loadgamebutton = new qpushbutton(tr("load game"));     exitgamebutton = new qpushbutton(tr("exit"));      qobject::connect(newgamebutton, signal(clicked()), this, signal(newgameclicked()));     qobject::connect(loadgamebutton, signal(clicked()), this, signal(loadgameclicked()));     qobject::connect(exitgamebutton, signal(clicked()), qapp, slot(quit()));      qvboxlayout* layout = new qvboxlayout();     layout->addwidget(newgamebutton);     layout->addwidget(loadgamebutton);     layout->addwidget(exitgamebutton);     layout->setcontentsmargins(300, 200, 300, 200);     setlayout(layout); }  void mainmenu::exit() {     if( qmessagebox::question(         this,         tr("exit?"),         tr("do want exit game?"),         qmessagebox::yes | qmessagebox::no,         qmessagebox::no         ) == qmessagebox::yes     )     {         qapp->quit();     } } 

main.cpp:

#include <qtgui>  #include "applicationwindow.h"  int main(int argv, char **args) {     qapplication app(argv, args);      applicationwindow window;     window.show();      return app.exec(); } 

so, how trigger behaviour or action when transition occurs?

cheers.

to on state transition, have connect triggered() signal of transition, e.g.

qabstracttransition* trmainload = mainmenustate->addtransition(mainmenu, signal(loadgameclicked()), loadgamemenustate); connect(trmainload , signal(triggered()), slot(...));