NetworkStateObserver

```
public interface NetworkStateObserver

                    
```
Contract for observing device network connectivity state. Implementations track online/offline transitions and notify registered listeners.
Typical lifecycle: obtain via ServiceLocator -> start -> add/remove listeners -> stop. isOnline may be called at any time; before start it reflects a one-time system query.

Method Summary

Modifier and Type	Method	Description
`abstract Boolean`	`isOnline()`	Returns the current connectivity state.
`abstract Unit`	`start()`	Begins observing connectivity changes.
`abstract Unit`	`stop()`	Stops observing and releases all system callbacks/receivers.
`abstract Unit`	`addListener(NetworkStateListener listener)`
`abstract Unit`	`removeListener(NetworkStateListener listener)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - isOnline
```
 abstract Boolean isOnline()
```
    Returns the current connectivity state. After start is called, this value is kept up-to-date reactively.
  - start
```
 abstract Unit start()
```
    Begins observing connectivity changes. Idempotent — subsequent calls are no-ops. Must be paired with stop to prevent resource leaks.
  - stop
```
 abstract Unit stop()
```
    Stops observing and releases all system callbacks/receivers. Idempotent — safe to call even if not started.
  - addListener
```
 abstract Unit addListener(NetworkStateListener listener)
```
  - removeListener
```
 abstract Unit removeListener(NetworkStateListener listener)
```