非同期処理には必ず絡んでくるのがライフサイクル。

RxJava のようにまとめたいですよね。

private CompositeDisposable compositeDisposable =
    new CompositeDisposable();

@Override public void onCreate() {
  compositeDisposable.add(backendApi.loadUser()
      .subscribe(this::displayUser, this::handleError));
}

@Override public void onDestroy() {
  compositeDisposable.clear();
}

SendChannel を使って同様にこのような。

interface JobHolder {
  val job: Job
}

class MainActivity : AppCompatActivity(), JobHolder {

  override val job: Job = Job()

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

    addJob {
      while (true) {
        delay(500)
        println("A")
      }
    }

    addJob {
      while (true) {
        delay(1000)
        println("B")
      }
    }

  }

  // Job の actor として action を登録する
  private fun addJob(action: suspend () -> Unit) {

    val actor = actor<Unit>(job + UI, capacity = Channel.CONFLATED) {
      for (event in channel) action()
    }
    actor.offer(Unit)
  }


  override fun onDestroy() {
    super.onDestroy()
    job.cancel()
  }

}

まとめてキャンセルできましたね!

どうせなら作って置いたらどうだろう。

class JobHolder {

  private val job = Job()

  fun add(action: suspend () -> Unit) {
    val actor = actor<Unit>(job + UI, capacity = Channel.CONFLATED) {
      for (event in channel) action()
    }
    actor.offer(Unit)
  }

  fun cancel() {
    job.cancel()
  }
}

Lifecycle and coroutine parent-child hierarchy
Children of a coroutine

 

こうでもいけるってよ: 2018-04-27追記

val rootParent = Job()

fun foo() {
  launch(UI, parent = rootParent) {
    // ...
  }
}

fun bar() {
  launch(CommonPool, parent = rootParent) {
    // ...
  }
}

fun destroy() { rootParent.cancel() }

Kotlin Coroutines on Android: Things I Wish I Knew at the Beginning

関連ワード:  Android・AndroidStudio・Kotlin・開発・SendChannel