# ObserverCallback

Artifact: [androidx.appsearch:appsearch](https://developer.android.com/jetpack/androidx/releases/appsearch) [View Source](https://cs.android.com/search?q=file:androidx/appsearch/observer/ObserverCallback.java+class:androidx.appsearch.observer.ObserverCallback) Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/appsearch#1.1.0)

*** ** * ** ***


```
interface ObserverCallback
```

<br />

*** ** * ** ***

An interface which apps can implement to subscribe to notifications of changes to AppSearch data.

## Summary

| ### Public functions |
|---|---|
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-unit/index.html` | `https://developer.android.com/reference/kotlin/androidx/appsearch/observer/ObserverCallback#onDocumentChanged(androidx.appsearch.observer.DocumentChangeInfo)(changeInfo: https://developer.android.com/reference/kotlin/androidx/appsearch/observer/DocumentChangeInfo)` Callback to trigger after document changes (documents added, updated or removed). |
| `https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/-unit/index.html` | `https://developer.android.com/reference/kotlin/androidx/appsearch/observer/ObserverCallback#onSchemaChanged(androidx.appsearch.observer.SchemaChangeInfo)(changeInfo: https://developer.android.com/reference/kotlin/androidx/appsearch/observer/SchemaChangeInfo)` Callback to trigger after schema changes (schema type added, updated or removed). |

## Public functions

### onDocumentChanged

Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/appsearch#1.1.0)

```
fun onDocumentChanged(changeInfo: DocumentChangeInfo): Unit
```

Callback to trigger after document changes (documents added, updated or removed).

| Parameters |
|---|---|
| `changeInfo: https://developer.android.com/reference/kotlin/androidx/appsearch/observer/DocumentChangeInfo` | Information about the nature of the change. |

### onSchemaChanged

Added in [1.1.0](https://developer.android.com/jetpack/androidx/releases/appsearch#1.1.0)

```
fun onSchemaChanged(changeInfo: SchemaChangeInfo): Unit
```

Callback to trigger after schema changes (schema type added, updated or removed).

| Parameters |
|---|---|
| `changeInfo: https://developer.android.com/reference/kotlin/androidx/appsearch/observer/SchemaChangeInfo` | Information about the nature of the change. |