# LifecycleEventObserver

Artifact: [androidx.lifecycle:lifecycle-common](https://developer.android.com/jetpack/androidx/releases/lifecycle) [View Source](https://cs.android.com/search?q=file:androidx/lifecycle/LifecycleEventObserver.kt+class:androidx.lifecycle.LifecycleEventObserver) Added in [2.1.0](https://developer.android.com/jetpack/androidx/releases/lifecycle#2.1.0)

*** ** * ** ***


```
public fun interface LifecycleEventObserver extends LifecycleObserver
```

<br />

*** ** * ** ***

Interface for receiving any `https://developer.android.com/reference/androidx/lifecycle/Lifecycle.Event` state changes.

If a class implements both this interface and `https://developer.android.com/reference/androidx/lifecycle/DefaultLifecycleObserver`, the methods of `https://developer.android.com/reference/androidx/lifecycle/DefaultLifecycleObserver` are called first, followed by `https://developer.android.com/reference/androidx/lifecycle/LifecycleEventObserver#onStateChanged(androidx.lifecycle.LifecycleOwner,androidx.lifecycle.Lifecycle.Event)`.

**Note:** If a class implements this interface and also uses the deprecated `androidx.lifecycle.OnLifecycleEvent` annotations, those annotations are ignored.

## Summary

| ### Public methods |
|---|---|
| `abstract void` | `https://developer.android.com/reference/androidx/lifecycle/LifecycleEventObserver#onStateChanged(androidx.lifecycle.LifecycleOwner,androidx.lifecycle.Lifecycle.Event)( @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/lifecycle/LifecycleOwner source, @https://developer.android.com/reference/androidx/annotation/NonNull https://developer.android.com/reference/androidx/lifecycle/Lifecycle.Event event )` Called when a state transition `https://developer.android.com/reference/androidx/lifecycle/LifecycleEventObserver#onStateChanged(androidx.lifecycle.LifecycleOwner,androidx.lifecycle.Lifecycle.Event)` occurs. |

## Public methods

### onStateChanged

Added in [2.1.0](https://developer.android.com/jetpack/androidx/releases/lifecycle#2.1.0)

```
abstract void onStateChanged(
    @NonNull LifecycleOwner source,
    @NonNull Lifecycle.Event event
)
```

Called when a state transition `https://developer.android.com/reference/androidx/lifecycle/LifecycleEventObserver#onStateChanged(androidx.lifecycle.LifecycleOwner,androidx.lifecycle.Lifecycle.Event)` occurs.