QHistoryState Class
The QHistoryState class provides a means of returning to a previously active substate. More...
Header: | #include <QHistoryState> |
qmake: | QT += core |
Since: | Qt 4.6 |
Inherits: | QAbstractState |
Public Types
enum | HistoryType { ShallowHistory, DeepHistory } |
Properties
- defaultState : QAbstractState *
- defaultTransition : QAbstractTransition *
- historyType : HistoryType
- 1 property inherited from QAbstractState
- 1 property inherited from QObject
Public Functions
QHistoryState(QState * parent = Q_NULLPTR) | |
QHistoryState(HistoryType type, QState * parent = Q_NULLPTR) | |
~QHistoryState() | |
QAbstractState * | defaultState() const |
QAbstractTransition * | defaultTransition() const |
HistoryType | historyType() const |
void | setDefaultState(QAbstractState * state) |
void | setDefaultTransition(QAbstractTransition * transition) |
void | setHistoryType(HistoryType type) |
- 3 public functions inherited from QAbstractState
- 31 public functions inherited from QObject
Signals
void | defaultStateChanged() |
void | defaultTransitionChanged() |
void | historyTypeChanged() |
- 3 signals inherited from QAbstractState
- 2 signals inherited from QObject
Reimplemented Protected Functions
virtual bool | event(QEvent * e) |
virtual void | onEntry(QEvent * event) |
virtual void | onExit(QEvent * event) |
- 3 protected functions inherited from QAbstractState
- 9 protected functions inherited from QObject
Additional Inherited Members
- 1 public slot inherited from QObject
- 11 static public members inherited from QObject
- 3 protected functions inherited from QAbstractState
- 9 protected functions inherited from QObject
Detailed Description
The QHistoryState class provides a means of returning to a previously active substate.
A history state is a pseudo-state that represents the child state that the parent state was in the last time the parent state was exited. A transition with a history state as its target is in fact a transition to one or more other child states of the parent state. QHistoryState is part of The State Machine Framework.
Use the setDefaultState() function to set the state that should be entered if the parent state has never been entered. Example:
QStateMachine machine; QState *s1 = new QState(); QState *s11 = new QState(s1); QState *s12 = new QState(s1); QHistoryState *s1h = new QHistoryState(s1); s1h->setDefaultState(s11); machine.addState(s1); QState *s2 = new QState(); machine.addState(s2); QPushButton *button = new QPushButton(); // Clicking the button will cause the state machine to enter the child state // that s1 was in the last time s1 was exited, or the history state's default // state if s1 has never been entered. s1->addTransition(button, SIGNAL(clicked()), s1h);
If more than one default state has to be entered, or if the transition to the default state(s) has to be acted upon, the defaultTransition should be set instead. Note that the eventTest() method of that transition will never be called: the selection and execution of the transition is done automatically when entering the history state.
By default a history state is shallow, meaning that it won't remember nested states. This can be configured through the historyType property.
Member Type Documentation
enum QHistoryState::HistoryType
This enum specifies the type of history that a QHistoryState records.
Constant | Value | Description |
---|---|---|
QHistoryState::ShallowHistory | 0 | Only the immediate child states of the parent state are recorded. In this case a transition with the history state as its target will end up in the immediate child state that the parent was in the last time it was exited. This is the default. |
QHistoryState::DeepHistory | 1 | Nested states are recorded. In this case a transition with the history state as its target will end up in the most deeply nested descendant state the parent was in the last time it was exited. |
Property Documentation
defaultState : QAbstractState *
This property holds the default state of this history state.
Access functions:
QAbstractState * | defaultState() const |
void | setDefaultState(QAbstractState * state) |
Notifier signal:
void | defaultStateChanged() | [see note below] |
Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
defaultTransition : QAbstractTransition *
This property holds the default transition of this history state.
Access functions:
QAbstractTransition * | defaultTransition() const |
void | setDefaultTransition(QAbstractTransition * transition) |
Notifier signal:
void | defaultTransitionChanged() | [see note below] |
Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
historyType : HistoryType
This property holds the type of history that this history state records.
The default value of this property is QHistoryState::ShallowHistory.
Access functions:
HistoryType | historyType() const |
void | setHistoryType(HistoryType type) |
Notifier signal:
void | historyTypeChanged() | [see note below] |
Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
Member Function Documentation
QHistoryState::QHistoryState(QState * parent = Q_NULLPTR)
Constructs a new shallow history state with the given parent state.
QHistoryState::QHistoryState(HistoryType type, QState * parent = Q_NULLPTR)
Constructs a new history state of the given type, with the given parent state.
QHistoryState::~QHistoryState()
Destroys this history state.
[virtual protected]
bool QHistoryState::event(QEvent * e)
Reimplemented from QObject::event().
[virtual protected]
void QHistoryState::onEntry(QEvent * event)
Reimplemented from QAbstractState::onEntry().
[virtual protected]
void QHistoryState::onExit(QEvent * event)
Reimplemented from QAbstractState::onExit().