QStateMachine ¶

概要 ¶

详细描述 ¶

QStateMachine is based on the concepts and notation of Statecharts . QStateMachine is part of 状态机框架 .

A state machine manages a set of states (classes that inherit from QAbstractState ) and transitions (descendants of QAbstractTransition ) between those states; these states and transitions define a state graph. Once a state graph has been built, the state machine can execute it. QStateMachine ‘s execution algorithm is based on the SCXML (状态图表 XML) algorithm. The framework’s 概述 gives several state graphs and the code to build them.

使用 addState() function to add a top-level state to the state machine. States are removed with the removeState() function. Removing states while the machine is running is discouraged.

Before the machine can be started, the initial state must be set. The initial state is the state that the machine enters when started. You can then start() the state machine. The started() signal is emitted when the initial state is entered.

The machine is event driven and keeps its own event loop. Events are posted to the machine through postEvent() . Note that this means that it executes asynchronously, and that it will not progress without a running event loop. You will normally not have to post events to the machine directly as Qt’s transitions, e.g., QEventTransition and its subclasses, handle this. But for custom transitions triggered by events, postEvent() is useful.

The state machine processes events and takes transitions until a top-level final state is entered; the state machine then emits the finished() signal. You can also stop() the state machine explicitly. The stopped() signal is emitted in this case.

The following snippet shows a state machine that will finish when a button is clicked:

button = QPushButton()
machine = QStateMachine()
s1 = QState()
s1.assignProperty(button, "text", "Click me")
s2 = QFinalState()
s1.addTransition(button, SIGNAL('clicked()'), s2)
machine.addState(s1)
machine.addState(s2)
machine.setInitialState(s1)
machine.start()
											

This code example uses QState , which inherits QAbstractState 。 QState class provides a state that you can use to set properties and invoke methods on QObject s when the state is entered or exited. It also contains convenience functions for adding transitions, e.g., QSignalTransition s as in this example. See the QState class description for further details.

If an error is encountered, the machine will look for an error state , and if one is available, it will enter this state. The types of errors possible are described by the Error enum. After the error state is entered, the type of the error can be retrieved with error() . The execution of the state graph will not stop when the error state is entered. If no error state applies to the erroneous state, the machine will stop executing and an error message will be printed to the console.

注意

Important: setting the ChildMode of a state machine to parallel ( ParallelStates ) results in an invalid state machine. It can only be set to (or kept as) ExclusiveStates .

另请参阅

QAbstractState QAbstractTransition QState 状态机框架

class QStateMachine ( [ parent=None ] ) ¶

QStateMachine(childMode[, parent=None])

param parent

QObject

param childMode

ChildMode

Constructs a new state machine with the given parent .

Constructs a new state machine with the given childMode and parent .

警告

Do not set the childMode to anything else than ExclusiveStates , otherwise the state machine is invalid, and might work incorrectly.

PySide2.QtCore.QStateMachine. EventPriority ¶

This enum type specifies the priority of an event posted to the state machine using postEvent() .

Events of high priority are processed before events of normal priority.

常量	描述
QStateMachine.NormalPriority	事件拥有正常优先级。
QStateMachine.HighPriority	事件拥有高优先级。

PySide2.QtCore.QStateMachine. Error ¶

This enum type defines errors that can occur in the state machine at run time. When the state machine encounters an unrecoverable error at run time, it will set the error code returned by error() , the error message returned by errorString() , and enter an error state based on the context of the error.

常量	描述
QStateMachine.NoError	没有发生错误。
QStateMachine.NoInitialStateError	The machine has entered a QState with children which does not have an initial state set. The context of this error is the state which is missing an initial state.
QStateMachine.NoDefaultStateInHistoryStateError	The machine has entered a QHistoryState which does not have a default state set. The context of this error is the QHistoryState which is missing a default state.
QStateMachine.NoCommonAncestorForTransitionError	The machine has selected a transition whose source and targets are not part of the same tree of states, and thus are not part of the same state machine. Commonly, this could mean that one of the states has not been given any parent or added to any machine. The context of this error is the source state of the transition.
QStateMachine.StateMachineChildModeSetToParallelError	The machine’s childMode property was set to ParallelStates . This is illegal. Only states may be declared as parallel, not the state machine itself. This enum value was added in Qt 5.14.

另请参阅

setErrorState()

PySide2.QtCore.QStateMachine. addDefaultAnimation ( animation ) ¶

参数

animation – QAbstractAnimation

Adds a default animation to be considered for any transition.

PySide2.QtCore.QStateMachine. addState ( state ) ¶

参数

state – QAbstractState

添加给定 state to this state machine. The state becomes a top-level state and the state machine takes ownership of the state.

If the state is already in a different machine, it will first be removed from its old machine, and then added to this machine.

另请参阅

removeState() setInitialState()

PySide2.QtCore.QStateMachine. beginMicrostep ( event ) ¶

参数

event – QEvent

This function is called when the state machine is about to do a microstep.

The default implementation does nothing.

PySide2.QtCore.QStateMachine. beginSelectTransitions ( event ) ¶

参数

event – QEvent

This function is called when the state machine is about to select transitions based on the given event .

The default implementation does nothing.

PySide2.QtCore.QStateMachine. cancelDelayedEvent ( id ) ¶

参数

id – int

返回类型

bool

Cancels the delayed event identified by the given id . The id should be a value returned by a call to postDelayedEvent() 。返回 true if the event was successfully cancelled, otherwise returns false .

另请参阅

postDelayedEvent()

PySide2.QtCore.QStateMachine. clearError ( ) ¶

Clears the error string and error code of the state machine.

PySide2.QtCore.QStateMachine. configuration ( ) ¶

返回类型

Returns the maximal consistent set of states (including parallel and final states) that this state machine is currently in. If a state s is in the configuration, it is always the case that the parent of s is also in c. Note, however, that the machine itself is not an explicit member of the configuration.

PySide2.QtCore.QStateMachine. endMicrostep ( event ) ¶

参数

event – QEvent

This function is called when the state machine has finished doing a microstep.

The default implementation does nothing.

PySide2.QtCore.QStateMachine. endSelectTransitions ( event ) ¶

参数

event – QEvent

This function is called when the state machine has finished selecting transitions based on the given event .

The default implementation does nothing.

PySide2.QtCore.QStateMachine. error ( ) ¶

返回类型

Error

Returns the error code of the last error that occurred in the state machine.

PySide2.QtCore.QStateMachine. errorString ( ) ¶

返回类型

unicode

Returns the error string of the last error that occurred in the state machine.

PySide2.QtCore.QStateMachine. globalRestorePolicy ( ) ¶

返回类型

RestorePolicy

Returns the restore policy of the state machine.

另请参阅

setGlobalRestorePolicy()

PySide2.QtCore.QStateMachine. isAnimated ( ) ¶

返回类型

bool

Returns whether animations are enabled for this state machine.

PySide2.QtCore.QStateMachine. isRunning ( ) ¶

返回类型

bool

PySide2.QtCore.QStateMachine. postDelayedEvent ( event , delay ) ¶

参数

• event – QEvent

• delay – int

返回类型

int

Posts the given event for processing by this state machine, with the given delay in milliseconds. Returns an identifier associated with the delayed event, or -1 if the event could not be posted.

This function returns immediately. When the delay has expired, the event will be added to the state machine’s event queue for processing. The state machine takes ownership of the event and deletes it once it has been processed.

You can only post events when the state machine is running.

另请参阅

cancelDelayedEvent() postEvent()

PySide2.QtCore.QStateMachine. postEvent ( event [ , priority=NormalPriority ] ) ¶

参数

• event – QEvent

• priority – EventPriority

Posts the given event 为给定 priority for processing by this state machine.

This function returns immediately. The event is added to the state machine’s event queue. Events are processed in the order posted. The state machine takes ownership of the event and deletes it once it has been processed.

You can only post events when the state machine is running or when it is starting up.

另请参阅

postDelayedEvent()

PySide2.QtCore.QStateMachine. removeDefaultAnimation ( animation ) ¶

参数

animation – QAbstractAnimation

移除 animation from the list of default animations.

PySide2.QtCore.QStateMachine. removeState ( state ) ¶

参数

state – QAbstractState

移除给定 state from this state machine. The state machine releases ownership of the state.

另请参阅

addState()

PySide2.QtCore.QStateMachine. runningChanged ( running ) ¶

参数

running – bool

PySide2.QtCore.QStateMachine. setAnimated ( enabled ) ¶

参数

enabled – bool

Sets whether animations are enabled for this state machine.

另请参阅

isAnimated()

PySide2.QtCore.QStateMachine. setGlobalRestorePolicy ( restorePolicy ) ¶

参数

restorePolicy – RestorePolicy

Sets the restore policy of the state machine to restorePolicy . The default restore policy is DontRestoreProperties .

另请参阅

globalRestorePolicy()

PySide2.QtCore.QStateMachine. setRunning ( running ) ¶

参数

running – bool

另请参阅

isRunning()

PySide2.QtCore.QStateMachine. start ( ) ¶

Starts this state machine. The machine will reset its configuration and transition to the initial state. When a final top-level state ( QFinalState ) is entered, the machine will emit the finished() 信号。

注意

A state machine will not run without a running event loop, such as the main application event loop started with exec() or exec() .

另请参阅

started() finished() stop() initialState() setRunning()

PySide2.QtCore.QStateMachine. stop ( ) ¶

Stops this state machine. The state machine will stop processing events and then emit the stopped() 信号。

另请参阅

stopped() start() setRunning()