Qt 状态机 事件迁移

class Window : public QWidget
{
public:
Window(QWidget *parent = 0)
: QWidget(parent)
{
QPushButton *button = new QPushButton(this);
button->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);

QVBoxLayout *layout = new QVBoxLayout;
layout->addWidget(button);
layout->setContentsMargins(80, 80, 80, 80);
setLayout(layout);
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();
}