---
title: "ComposeNodeLifecycleCallback"
description: "Observes lifecycle of the node emitted with [ReusableComposeNode] or [ComposeNode] inside
[ReusableContentHost] and [ReusableContent].

The [ReusableContentHost] introduces the concept of reusing (or recycling) nodes, as well as
deactivating parts of composition, while keeping the nodes around to reuse common structures in
the next iteration. In this state, [RememberObserver] is not sufficient to track lifetime of data
associated with reused node, as deactivated or reused parts of composition is disposed.

These callbacks track intermediate states of the node in reusable groups for managing data
contained inside reusable nodes or associated with them (e.g. subcomposition).

Important: the runtime only supports node implementation of this interface."
type: "interface"
---

<div class='type'>Interface</div>


<a id='references'></a>

<div class='sourceset sourceset-common'>Common</div>



```kotlin
public interface ComposeNodeLifecycleCallback
```


Observes lifecycle of the node emitted with `ReusableComposeNode` or `ComposeNode` inside
`ReusableContentHost` and `ReusableContent`.

The `ReusableContentHost` introduces the concept of reusing (or recycling) nodes, as well as
deactivating parts of composition, while keeping the nodes around to reuse common structures in
the next iteration. In this state, `RememberObserver` is not sufficient to track lifetime of data
associated with reused node, as deactivated or reused parts of composition is disposed.

These callbacks track intermediate states of the node in reusable groups for managing data
contained inside reusable nodes or associated with them (e.g. subcomposition).

Important: the runtime only supports node implementation of this interface.


## Functions

```kotlin
public fun onReuse()
```


Invoked when the node was reused in the composition. Consumers might use this callback to
reset data associated with the previous content, as it is no longer valid.


```kotlin
public fun onDeactivate()
```


Invoked when the group containing the node was deactivated. This happens when the content of
`ReusableContentHost` is deactivated.

The node will not be reused in this recompose cycle, but might be reused or released in the
future. Consumers might use this callback to release expensive resources or stop continuous
process that was dependent on the node being used in composition.

If the node is reused, `onReuse` will be called again to prepare the node for reuse.
Similarly, `onRelease` will indicate that deactivated node will never be reused again.


```kotlin
public fun onRelease()
```


Invoked when the node exits the composition entirely and won't be reused again. All
intermediate data related to the node can be safely disposed.