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In this article, the editor introduces in detail "what is the use of the state of Android", the content is detailed, the steps are clear, and the details are handled properly. I hope this article "what is the use of the state of Android" can help you solve your doubts.

A state can have an entry behavior. If this behavior is defined, it will be executed whenever it enters the state through an external migration. In addition, a state can have an associated exit behavior, and if this behavior is defined, it will be executed whenever the state exits.

A state can also have a doActivity behavior. This behavior starts when the state enters (but only after the state entry behavior ends) and is executed at the same time as any other behavior associated with the state. Until:

It completes (in which case a completion event is generated) or

It ends itself (in this case a finished event is generated)

The State is exited, in which case execution of the doActivity Behavior is aborted.

The state exits, in which case the execution of the doActivity behavior is interrupted.

The execution of a doActivity Behavior of a State is not affected by the firing of an internal Transition of that State.

The execution of the doActivity behavior of the state is not triggered by the internal migration of the state.

Historical state

The concept of historical state is introduced into the original state diagram system by DavidHarel. This is a concept of convenience related to a region in a combined state, through which an area can maintain the trace of its previous exit state. If you prefer, you can restore to the same state composition in an easy way when the next state is activated, or if there is a local migration that returns the historical state (for example, from interrupt handling). This can be done simply by terminating the migration in a historical pseudo-state of the desired type in an area. The advantage of this approach is that there is no need to accurately maintain the traces of the state composition when the user has a need. The result is a simpler state machine model.

There are two types of historical pseudo-states. Deep history (deepHistory) represents the complete state composition of the region that contains it. The effect equates the effect of a migration terminated with the deepHistory history pseudo state as if the migration terminated with a substate in the innermost layer of the saved state, including the execution of all entry behaviors encountered along the way. Shallow history (shallowHistory) represents the uppermost state of returning the most recent state, which applies to the default entry rules when entering.

There is a situation in which the state has not been entered (that is, there is no previous history) or has reached the terminated state, and if the migration exists and terminates on the historical pseudo state, you can use the default history mechanism to force it to migrate to a specific substate. This is a migration that starts in a historical pseudo-state and ends at a specific vertex (the default historical state) in the area that contains the historical pseudo-state. This migration occurs only if the state is executed to a historical pseudo state and the state has never been activated. Otherwise, the appropriate historical entrance to the area will be performed (see above). If no default historical migration is defined, the standard regional default entry behavior is executed as explained later.

Postponement event

A state can define a set of time types that are delayed in that state. This means that as long as the state remains active, those types of events do not occur until:

A state composition reaches a location where these event types are not delayed.

If a delay event is explicitly used in the trigger condition of a migration with the delay state (an override option) as the source.

An event can be delayed by a combined state or a sub-state machine state, and it continues to be delayed as long as the combined state is still in the active state composition.

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