Integrate Lifecycle with Compose

The Lifecycle library offers built-in APIs that let you integrate with Jetpack Compose. Key APIs include the following:

• Flows for the current Lifecycle.State.
• LifecycleEffects that lets you run a block based on a specific Lifecycle.Event.

These integrations provide convenient hooks to manage Lifecycles within the Compose hierarchy. This document outlines how you can use them in your app.

Collect lifecycle state with flows

Lifecycle exposes a currentStateFlow property that provides the current Lifecycle.State as a Kotlin StateFlow. You can collect this Flow as State. This allows your app to read changes in the Lifecycle during composition.

val lifecycleOwner = LocalLifecycleOwner.current
val stateFlow = lifecycleOwner.lifecycle.currentStateFlow
…
val currentLifecycleState by stateFlow.collectAsState()

The preceding example is accessible using the lifecycle-common module. The currentStateAsState() method is available in the lifecycle-runtime-compose module, which lets you conveniently read the current Lifecycle state with a single line. The following example demonstrates this:

val lifecycleOwner = LocalLifecycleOwner.current
val currentLifecycleState = lifecycleOwner.lifecycle.currentStateAsState()

Run code on lifecycle events

There are also LifecycleEffects that let you run a block when a particular Lifecycle.Event occurs.

LifecycleEventEffect(Lifecycle.Event.ON_START) {
  // do something here
}

In addition to the LifecycleEventEffect, you can also use LifecycleStartEffect and LifecycleResumeEffect. These APIs are tied to specific events. They also offer an additional block within their primary block that helps clean up any code that the event might have kicked off.

LifecycleStartEffect

The LifecycleStartEffect is similar to the LifecycleEffect, but it runs only on Lifecycle.Event.ON_START events. It also accepts keys that work like other Compose keys. When the key changes, it triggers the block to run again.

When there is a Lifecycle.Event.ON_STOP event or the effect exits composition, it executes a onStopOrDispose block. This allows for the clean up of any work that was part of the starting block.

LifecycleStartEffect {
  // ON_START code is executed here

  onStopOrDispose {
    // do any needed clean up here
  }
}

LifecycleResumeEffect

The LifecycleResumeEffect works in the same way as the LifecycleStartedEffect, but it executes on the Lifecycle.Event.ON_RESUME event instead. It also provides an onPauseOrDispose block that performs the clean up.

LifecycleResumeEffect {
  // ON_RESUME code is executed here

  onPauseOrDispose {
    // do any needed clean up here
  }
}