Event Transitions ExampleFiles: The Event Transitions example shows how to use event transitions, a feature of The State Machine Framework. class Window : public QWidget { public: Window(QWidget *parent = 0) : QWidget(parent) { QPushButton *button = new QPushButton(this); button->setGeometry(QRect(100, 100, 100, 100)); The Window class's constructors begins by creating a button. QStateMachine *machine = new QStateMachine(this); QState *s1 = new QState(); s1->assignProperty(button, "text", "Outside"); QState *s2 = new QState(); s2->assignProperty(button, "text", "Inside"); Two states, s1 and s2, are created; upon entry they will assign "Outside" and "Inside" to the button's text, respectively. QEventTransition *enterTransition = new QEventTransition(button, QEvent::Enter); enterTransition->setTargetState(s2); s1->addTransition(enterTransition); When the button receives an event of type QEvent::Enter and the state machine is in state s1, the machine will transition to state s2. QEventTransition *leaveTransition = new QEventTransition(button, QEvent::Leave); leaveTransition->setTargetState(s1); s2->addTransition(leaveTransition); When the button receives an event of type QEvent::Leave and the state machine is in state s2, the machine will transition back to state s1. QState *s3 = new QState(); s3->assignProperty(button, "text", "Pressing..."); QEventTransition *pressTransition = new QEventTransition(button, QEvent::MouseButtonPress); pressTransition->setTargetState(s3); s2->addTransition(pressTransition); QEventTransition *releaseTransition = new QEventTransition(button, QEvent::MouseButtonRelease); releaseTransition->setTargetState(s2); s3->addTransition(releaseTransition); Next, the state s3 is created. s3 will be entered when the button receives an event of type QEvent::MouseButtonPress and the state machine is in state s2. When the button receives an event of type QEvent::MouseButtonRelease and the state machine is in state s3, the machine will transition back to state s2. machine->addState(s1); machine->addState(s2); machine->addState(s3); machine->setInitialState(s1); machine->start(); } }; Finally, the states are added to the machine as top-level states, the initial state is set to be s1 ("Outside"), and the machine is started. int main(int argc, char **argv) { QApplication app(argc, argv); Window window; window.resize(300, 300); window.show(); return app.exec(); } The main() function constructs a Window object and shows it. © 2008-2011 Nokia Corporation and/or its subsidiaries. Nokia, Qt and their respective logos are trademarks of Nokia Corporation in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. Privacy Policy Licensees holding valid Qt Commercial licenses may use this document in accordance with the Qt Commercial License Agreement provided with the Software or, alternatively, in accordance with the terms contained in a written agreement between you and Nokia. Alternatively, this document may be used under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. |