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This article mainly explains "what is the concept of state in android", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let Xiaobian take you to learn "what is the concept of state in android"!

1. Status

A state models a situation in the execution of state machine behavior where certain conditions remain unchanged. In most cases, this condition is not explicitly defined, but implicitly defined by the name associated with the state. For example, in Figure 14.36, which models the telephone unit, the states idel and Active represent the telephone not in use and in use, respectively. This example also illustrates the fact that the state does not necessarily represent a completely static situation, because obviously some detail activity occurs in the context of the "Activie" state. But the phone remains in use (i.e.:Active) for the entire period that includes all activity.

2. Type of state

The states are classified as follows:

· simple State (isSimple = true)

Simple state (isSimple is true)

· composite State (isComposite = true)

Composite state (isComposite is true)

· submachine State (isSubmachineState = true)

SubmachineState (isSubmachineState is true)

Simple states have no internal vertices and transitions. The composite state contains at least one region, whereas the sub-state machine states refer to a complete state machine, which can conceptually be seen as embedded in the state. Combinatorial states are either simple combinational states with only one region or orthogonal states with multiple regions (isOrgonal is true). For example, in Figure 14.9,"CourseAttempt" is an example of a simple state containing a separate region. The "Studying" state is a composite state with three regions.

The states encapsulated inside the combined state region are made sub-states of the combined state. If it is not contained by another state, it is called a direct child state; otherwise, it is referenced as an indirect child state.

3. Status Configuration

In general, a state machine can have multiple regions, each region can contain its own state, some regions can consist of multiple regions they own, and so on. Thus, a certain "state" of an executing state machine instance can appear as one or more levels of state. Start at the top of the state machine and work your way down through the composition hierarchy to simple, or leaf, states. Similarly, we can discuss a hierarchy of child states within a composite state. This complex hierarchy of states is constructed as a state (state or state machine). For example, a valid state construct executed by the state machine depicted in Figure 14.9 is. An executing state machine instance can have only one state component at a time, which is called an active state component. The execution of the state machine is represented as a transition from one state configuration to another, and the transition occurs when an event matching the state machine transition condition occurs.

A state is said to be active if it is part of an active state.

The state composition can be said to be stable if:

There is no valid further migration from this state, and

All existing entry behaviors for this state have ended (but the doActivity behavior for this state does not have to end; it may be defined as persistent).

When a state machine is created and the initial migration is complete, it is always in some state configuration. However, because states are hierarchical and because there can be behaviors associated with transitions and states,"entering" a hierarchical state composition involves a dynamic process that ends only when a stable state composition (defined above) is reached. A state machine is in a specific state of a state composition, and there are some potential ambiguities. The rules for when a state machine can be considered to be in a state and when it can be considered to be 'out of' a state are discussed later in the "Entering a State" and "Leaving a State" sections, respectively.

Even if there are delays, completions, or other types of events waiting to be processed in the event pool of the state machine, the state composition can still be considered stable.

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