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Diffstat (limited to 'doc/src/statemachine.qdoc')
| -rw-r--r-- | doc/src/statemachine.qdoc | 315 |
1 files changed, 103 insertions, 212 deletions
diff --git a/doc/src/statemachine.qdoc b/doc/src/statemachine.qdoc index 5a89f4d..d2b508d 100644 --- a/doc/src/statemachine.qdoc +++ b/doc/src/statemachine.qdoc @@ -1,7 +1,7 @@ /**************************************************************************** ** ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). -** Contact: Qt Software Information (qt-info@nokia.com) +** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation of the Qt Toolkit. ** @@ -34,7 +34,7 @@ ** met: http://www.gnu.org/copyleft/gpl.html. ** ** If you are unsure which license is appropriate for your use, please -** contact the sales department at qt-sales@nokia.com. +** contact the sales department at http://www.qtsoftware.com/contact. ** $QT_END_LICENSE$ ** ****************************************************************************/ @@ -85,36 +85,20 @@ The following snippet shows the code needed to create such a state machine. First, we create the state machine and states: - \code - QStateMachine machine; - QState *s1 = new QState(); - QState *s2 = new QState(); - QState *s3 = new QState(); - \endcode + \snippet doc/src/snippets/statemachine/main.cpp 0 Then, we create the transitions by using the QState::addTransition() function: - \code - s1->addTransition(button, SIGNAL(clicked()), s2); - s2->addTransition(button, SIGNAL(clicked()), s3); - s3->addTransition(button, SIGNAL(clicked()), s1); - \endcode + \snippet doc/src/snippets/statemachine/main.cpp 1 Next, we add the states to the machine and set the machine's initial state: - \code - machine.addState(s1); - machine.addState(s2); - machine.addState(s3); - machine.setInitialState(s1); - \endcode + \snippet doc/src/snippets/statemachine/main.cpp 2 Finally, we start the state machine: - \code - machine.start(); - \endcode + \snippet doc/src/snippets/statemachine/main.cpp 3 The state machine executes asynchronously, i.e. it becomes part of your application's event loop. @@ -127,11 +111,7 @@ entered. In the following snippet, the value that should be assigned to a QLabel's text property is specified for each state: - \code - s1->assignProperty(label, "text", "In state s1"); - s2->assignProperty(label, "text", "In state s2"); - s3->assignProperty(label, "text", "In state s3"); - \endcode + \snippet doc/src/snippets/statemachine/main.cpp 4 When any of the states is entered, the label's text will be changed accordingly. @@ -142,10 +122,7 @@ state \c s3 is entered, and the button's showMinimized() slot will be called when \c s3 is exited: - \code - QObject::connect(s3, SIGNAL(entered()), button, SLOT(showMaximized())); - QObject::connect(s3, SIGNAL(exited()), button, SLOT(showMinimized())); - \endcode + \snippet doc/src/snippets/statemachine/main.cpp 5 Custom states can reimplement QAbstractState::onEntry() and QAbstractState::onExit(). @@ -194,22 +171,9 @@ initial one (i.e. which child state the state machine should enter when the parent state is the target of a transition). - \code - QState *s1 = new QState(); - QState *s11 = new QState(s1); - QState *s12 = new QState(s1); - QState *s13 = new QState(s1); - s1->setInitialState(s11); - machine.addState(s1); - \endcode + \snippet doc/src/snippets/statemachine/main2.cpp 0 - \code - QFinalState *s2 = new QFinalState(); - s1->addTransition(quitButton, SIGNAL(clicked()), s2); - machine.addState(s2); - - QObject::connect(&machine, SIGNAL(finished()), QApplication::instance(), SLOT(quit())); - \endcode + \snippet doc/src/snippets/statemachine/main2.cpp 1 In this case we want the application to quit when the state machine is finished, so the machine's finished() signal is connected to the @@ -219,9 +183,7 @@ following code adds a transition that effectively causes the Quit button to be ignored when the state machine is in state \c s12. - \code - s12>addTransition(quitButton, SIGNAL(clicked()), s12); - \endcode + \snippet doc/src/snippets/statemachine/main2.cpp 2 A transition can have any state as its target, i.e. the target state does not have to be on the same level in the state hierarchy as the source state. @@ -259,21 +221,7 @@ simply display a message box when \c s3 is entered, then immediately return to the previous child state of \c s1 via the history state. - \code - QHistoryState *s1h = s1->addHistoryState(); - - QState *s3 = new QState(); - s3->assignProperty(label, "text", "In s3"); - QMessageBox mbox; - mbox.addButton(QMessageBox::Ok); - mbox.setText("Interrupted!"); - mbox.setIcon(QMessageBox::Information); - QObject::connect(s3, SIGNAL(entered()), &mbox, SLOT(exec())); - s3->addTransition(s1h); - machine.addState(s3); - - s1->addTransition(interruptButton, SIGNAL(clicked()), s3); - \endcode + \snippet doc/src/snippets/statemachine/main2.cpp 3 \section1 Using Parallel States to Avoid a Combinatorial Explosion of States @@ -305,12 +253,7 @@ To create a parallel state group, pass QState::ParallelStates to the QState constructor. - \code - QState *s1 = new QState(QState::ParallelStates); - // s11 and s12 will be entered in parallel - QState *s11 = new QState(s1); - QState *s12 = new QState(s1); - \endcode + \snippet doc/src/snippets/statemachine/main3.cpp 0 When a parallel state group is entered, all its child states will be simultaneously entered. Transitions within the individual child states @@ -334,9 +277,7 @@ finished(). We use a signal transition to cause this event to trigger a state change: - \code - s1->addTransition(s1, SIGNAL(finished()), s2); - \endcode + \snippet doc/src/snippets/statemachine/main3.cpp 1 Using final states in composite states is useful when you want to hide the internal details of a composite state; i.e. the only thing the outside world @@ -372,42 +313,12 @@ Here we define our own custom event type, \c StringEvent, for posting strings to the state machine: - \code - struct StringEvent : public QEvent - { - StringEvent(const QString &val) - : QEvent(QEvent::Type(QEvent::User+1)), - value(val) {} - - QString value; - }; - \endcode + \snippet doc/src/snippets/statemachine/main4.cpp 0 Next, we define a transition that only triggers when the event's string matches a particular string (a \e guarded transition): - \code - class StringTransition : public QAbstractTransition - { - public: - StringTransition(const QString &value) - : m_value(value) {} - - protected: - virtual bool eventTest(QEvent *e) const - { - if (e->type() != QEvent::Type(QEvent::User+1)) // StringEvent - return false; - StringEvent *se = static_cast<StringEvent*>(e); - return (m_value == se->value); - } - - virtual void onTransition(QEvent *) {} - - private: - QString m_value; - }; - \endcode + \snippet doc/src/snippets/statemachine/main4.cpp 1 In the eventTest() reimplementation, we first check if the event type is the desired one; if so, we cast the event to a StringEvent and perform the @@ -422,31 +333,11 @@ Here's what the implementation of the statechart looks like: - \code - QStateMachine machine; - QState *s1 = new QState(); - QState *s2 = new QState(); - QFinalState *done = new QFinalState(); - - StringTransition *t1 = new StringTransition("Hello"); - t1->setTargetState(s2); - s1->addTransition(t1); - StringTransition *t2 = new StringTransition("world"); - t2->setTargetState(done); - s2->addTransition(t2); - - machine.addState(s1); - machine.addState(s2); - machine.addState(done); - machine.setInitialState(s1); - \endcode + \snippet doc/src/snippets/statemachine/main4.cpp 2 Once the machine is started, we can post events to it. - \code - machine.postEvent(new StringEvent("Hello")); - machine.postEvent(new StringEvent("world")); - \endcode + \snippet doc/src/snippets/statemachine/main4.cpp 3 An event that is not handled by any relevant transition will be silently consumed by the state machine. It can be useful to group states and provide @@ -462,184 +353,184 @@ the level of granularity that's most appropriate. \section1 Using Restore Policy To Automatically Restore Properties - + In some state machines it can be useful to focus the attention on assigning properties in states, not on restoring them when the state is no longer active. If you know that a property should - always be restored to its initial value when the machine enters a state that does not explicitly - give the property a value, you can set the global restore policy to - QStateMachine::RestoreProperties. - + always be restored to its initial value when the machine enters a state that does not explicitly + give the property a value, you can set the global restore policy to + QStateMachine::RestoreProperties. + \code QStateMachine machine; machine.setGlobalRestorePolicy(QStateMachine::RestoreProperties); \endcode - + When this restore policy is set, the machine will automatically restore all properties. If it enters a state where a given property is not set, it will first search the hierarchy of ancestors to see if the property is defined there. If it is, the property will be restored to the value - defined by the closest ancestor. If not, it will be restored to its initial value (i.e. the + defined by the closest ancestor. If not, it will be restored to its initial value (i.e. the value of the property before any property assignments in states were executed.) - + Take the following code: \code QStateMachine machine; machine.setGlobalRestorePolicy(QStateMachine::RestoreProperties); - + QState *s1 = new QState(); s1->assignProperty(object, "fooBar", 1.0); machine.addState(s1); machine.setInitialState(s1); - - QState *s2 = new QState(); + + QState *s2 = new QState(); machine.addState(s2); \endcode - - Lets say the property \c fooBar is 0.0 when the machine starts. When the machine is in state + + Lets say the property \c fooBar is 0.0 when the machine starts. When the machine is in state \c s1, the property will be 1.0, since the state explicitly assigns this value to it. When the machine is in state \c s2, no value is explicitly defined for the property, so it will implicitly be restored to 0.0. - - If we are using nested states, the parent defines a value for the property which is inherited by + + If we are using nested states, the parent defines a value for the property which is inherited by all descendants that do not explicitly assign a value to the property. \code QStateMachine machine; machine.setGlobalRestorePolicy(QStateMachine::RestoreProperties); - + QState *s1 = new QState(); s1->assignProperty(object, "fooBar", 1.0); machine.addState(s1); machine.setInitialState(s1); - - QState *s2 = new QState(s1); + + QState *s2 = new QState(s1); s2->assignProperty(object, "fooBar", 2.0); s1->setInitialState(s2); - + QState *s3 = new QState(s1); \endcode - - Here \c s1 has two children: \c s2 and \c s3. When \c s2 is entered, the property \c fooBar + + Here \c s1 has two children: \c s2 and \c s3. When \c s2 is entered, the property \c fooBar will have the value 2.0, since this is explicitly defined for the state. When the machine is in state \c s3, no value is defined for the state, but \c s1 defines the property to be 1.0, so this - is the value that will be assigned to \c fooBar. - + is the value that will be assigned to \c fooBar. + \section1 Animating Property Assignments - - The State Machine API connects with the Animation API in Qt to allow automatically animating - properties as they are assigned in states. - + + The State Machine API connects with the Animation API in Qt to allow automatically animating + properties as they are assigned in states. + Say we have the following code: - \code + \code QState *s1 = new QState(); - QState *s2 = new QState(); - + QState *s2 = new QState(); + s1->assignProperty(button, "geometry", QRectF(0, 0, 50, 50)); s2->assignProperty(button, "geometry", QRectF(0, 0, 100, 100)); - + s1->addTransition(button, SIGNAL(clicked()), s2); \endcode - + Here we define two states of a user interface. In \c s1 the \c button is small, and in \c s2 - it is bigger. If we click the button to transition from \c s1 to \c s2, the geometry of the button - will be set immediately when a given state has been entered. If we want the transition to be + it is bigger. If we click the button to transition from \c s1 to \c s2, the geometry of the button + will be set immediately when a given state has been entered. If we want the transition to be smooth, however, all we need to do is make a QPropertyAnimation and add this to the transition object. - - \code + + \code QState *s1 = new QState(); - QState *s2 = new QState(); - + QState *s2 = new QState(); + s1->assignProperty(button, "geometry", QRectF(0, 0, 50, 50)); s2->assignProperty(button, "geometry", QRectF(0, 0, 100, 100)); - + QSignalTransition *transition = s1->addTransition(button, SIGNAL(clicked()), s2); transition->addAnimation(new QPropertyAnimation(button, "geometry")); \endcode - + Adding an animation for the property in question means that the property assignment will no longer take immediate effect when the state has been entered. Instead, the animation will start playing when the state has been entered and smoothly animate the property assignment. Since we - do not set the start value or end value of the animation, these will be set implicitly. The + do not set the start value or end value of the animation, these will be set implicitly. The start value of the animation will be the property's current value when the animation starts, and the end value will be set based on the property assignments defined for the state. - + If the global restore policy of the state machine is set to QStateMachine::RestoreProperties, it is possible to also add animations for the property restorations. - + \section1 Detecting That All Properties Have Been Set In A State - - When animations are used to assign properties, a state no longer defines the exact values that a + + When animations are used to assign properties, a state no longer defines the exact values that a property will have when the machine is in the given state. While the animation is running, the - property can potentially have any value, depending on the animation. - + property can potentially have any value, depending on the animation. + In some cases, it can be useful to be able to detect when the property has actually been assigned the value defined by a state. For this, we can use the state's polished() signal. \code QState *s1 = new QState(); s1->assignProperty(button, "geometry", QRectF(0, 0, 50, 50)); - + QState *s2 = new QState(); - + s1->addTransition(s1, SIGNAL(polished()), s2); \endcode - - The machine will be in state \c s1 until the \c geometry property has been set. Then it will + + The machine will be in state \c s1 until the \c geometry property has been set. Then it will immediately transition into \c s2. If the transition into \c s1 has an animation for the \c geometry property, then the machine will stay in \c s1 until the animation has finished. If there is no animation, it will simply set the property and immediately enter state \c s2. - - Either way, when the machine is in state \c s2, the property \c geometry has been assigned the + + Either way, when the machine is in state \c s2, the property \c geometry has been assigned the defined value. - + If the global restore policy is set to QStateMachine::RestoreProperties, the state will not emit the polished() signal until these have been executed as well. - + \section1 What happens if a state is exited before the animation has finished - - If a state has property assignments, and the transition into the state has animations for the - properties, the state can potentially be exited before the properties have been assigned to the - values defines by the state. This is true in particular when there are transitions out from the + + If a state has property assignments, and the transition into the state has animations for the + properties, the state can potentially be exited before the properties have been assigned to the + values defines by the state. This is true in particular when there are transitions out from the state that do not depend on the state being polished, as described in the previous section. - - The State Machine API guarantees that a property assigned by the state machine either: + + The State Machine API guarantees that a property assigned by the state machine either: \list \o Has a value explicitly assigned to the property. \o Is currently being animated into a value explicitly assigned to the property. \endlist - + When a state is exited prior to the animation finishing, the behavior of the state machine depends - on the target state of the transition. If the target state explicitly assigns a value to the + on the target state of the transition. If the target state explicitly assigns a value to the property, no additional action will be taken. The property will be assigned the value defined by - the target state. - + the target state. + If the target state does not assign any value to the property, there are two options: By default, the property will be assigned the value defined by the state it is leaving - (the value it would have been assigned if the animation had been permitted to finish playing.) If - a global restore policy is set, however, this will take precedence, and the property will be + (the value it would have been assigned if the animation had been permitted to finish playing.) If + a global restore policy is set, however, this will take precedence, and the property will be restored as usual. - + \section1 Default Animations - + As described earlier, you can add animations to transitions to make sure property assignments in the target state are animated. If you want a specific animation to be used for a given property - regardless of which transition is taken, you can add it as a default animation to the state - machine. This is in particular useful when the properties assigned (or restored) by specific - states is not known when the machine is constructed. - - \code + regardless of which transition is taken, you can add it as a default animation to the state + machine. This is in particular useful when the properties assigned (or restored) by specific + states is not known when the machine is constructed. + + \code QState *s1 = new QState(); QState *s2 = new QState(); - + s2->assignProperty(object, "fooBar", 2.0); - s1->addTransition(s2); - + s1->addTransition(s2); + QStateMachine machine; machine.setInitialState(s1); - machine.addDefaultAnimation(new QPropertyAnimation(object, "fooBar")); - \endcode - - When the machine is in state \c s2, the machine will play the default animation for the - property \c fooBar since this property is assigned by \c s2. - - Note that animations explicitly set on transitions will take precedence over any default - animation for the given property. + machine.addDefaultAnimation(new QPropertyAnimation(object, "fooBar")); + \endcode + + When the machine is in state \c s2, the machine will play the default animation for the + property \c fooBar since this property is assigned by \c s2. + + Note that animations explicitly set on transitions will take precedence over any default + animation for the given property. */ |