Coroutine Lifecycle Handler

This library is a glue between the lifecycle of androidx.lifecycle:lifecycle-extensions and Flow class of org.jetbrains.kotlinx:kotlinx-coroutines-core library. The assumption is that we want the emitted values between start and stop of LifecycleOwner, so on other moments this library would unsubscribe from the upstream of Flow. Also, we support a more general assumption that we want the emitted values after start and before stop or saveState of SavedStateRegistryOwner, depends which one gets called sooner.

Also you can find its twin library for RxJava in https://github.com/hadilq/RxLifecycleHandler/.

Usage

This source has a sample app, which doesn't do anything, where you can find the usage in MainActivity, MainViewModelActivity and ScopeMainActivity. However, in MVVM or MVI architectural patterns, you can use it based on the data you want to save in onSaveInstanceState or not. For now let's restrict ourselves to MVVM. If the data you want to propagate is an action, then you probably don't want to save it so in ViewModel you have.

class MainViewModel : ViewModel() {

    private val publisher = BroadcastChannel<String>(CONFLATED)
    val stringEmitter = publisher.toLifecycleAware()
}

And in the Activity or Fragment you have.

class MyViewModelActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main_activity)

        val viewModel = ViewModelProvider(this).get(MainViewModel::class.java)

        (viewModel.stringEmitter.observe()) { testString ->
            /* use it here */
        }
    }
}

But if you want to save the propagated data in onSaveInstanceState method, then you may want to use it as follows.

class MainViewModel : ViewModel() {

    private val extendedPublisher = BroadcastChannel<String>(CONFLATED)

    val extendedStringEmitter = extendedPublisher.toELifeAware(KEY)

    companion object {
        private const val KEY = "key_to_save_string_emitter"
    }
}

And in the Activity or Fragment you have.

class MyViewModelActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main_activity)

        val viewModel = ViewModelProvider(this).get(MainViewModel::class.java)

        (viewModel.extendedStringEmitter.observe()) { testString ->
            /* use it here */
        }
    }
}

Here, you may noticed the extra parentheses above, or you may noticed that we didn't passe the Activity or Fragment to the observe method. In both cases, read the last sentence again! Because they're related to each other, which means in this library we preferred to avoid writing this to pass the Activity or Fragment directly in trade off of having odd position of parentheses.

Any way, in case you want to use this library out of MVVM architectural pattern, you can use it as follows.

class MainActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        ...

        val flow: Flow<String> = ...
        
        // Flow usage
        flow
            .onEach { }
            .catch { }
            .onCompletion { }
            .observeIn()()

        // OR
        flow
            .onEach { }
            .catch { }
            .onCompletion { }
            .observeIn(life, KEY)()
    }

    companion object {
        private const val KEY = "key_to_save_the_data"
    }
}

Enjoy!

Download

Since version 0.4.0 this library is a Kotlin Multiplatform library, so depend on what kind of module you use it in, you can use different artifact IDs. Download via gradle

implementation "com.github.hadilq:coroutines-lifecycle-handler-android:$libVersion"

where the libVersion is . Use the above one if you already using this library or you need it in an android module. Use

implementation "com.github.hadilq:coroutines-lifecycle-handler-jvm:$libVersion"

if you need only the interfaces in a Java module. And finally, in a common module of multiplatform project you would use those interfaces as

implementation "com.github.hadilq:coroutines-lifecycle-handler-metadata:$libVersion"

Contribution

Just create your branch from the master branch, change it, write additional tests, satisfy all tests, create your pull request, thank you, you're awesome.