LifecycleControlledCountDownTimer a wrapper class around CountDownTimer

LifecycleControlledCountDownTimer.kt

import android.os.CountDownTimer
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleObserver
import androidx.lifecycle.LifecycleOwner
import androidx.lifecycle.OnLifecycleEvent
import timber.log.Timber


interface LifecycleControlledCountDownTimer {
  
  fun start(
    onIntervalTick: (millisUntilFinished: Long) -> Unit,
    onFinished: () -> Unit
  )

  fun cancel(callFinish: Boolean)
  
}

/**
 * A [CountDownTimer] which stop itself if the lifecycle goes to [Lifecycle.State.PAUSE] state.
 * If paused by Lifecycle [onFinished] will not be called automatically, you need to handle this case yourself
 *
 * Can be manually started using [start] and canceled with [cancel]
 */
private class LifecycleControlledCountDownTimerImpl constructor(
  private val lifecycleOwner: LifecycleOwner,
  private val durationMillis: Long,
  private val intervalMillis: Long
): LifecycleControlledCountDownTimer, LifecycleObserver {

  private var countDownTimer: CountDownTimer? = null

  init {
    lifecycleOwner.lifecycle.addObserver(this)
  }

  override fun start(
    onIntervalTick: (millisUntilFinished: Long) -> Unit,
    onFinished: () -> Unit
  ) {
    if (lifecycleOwner.lifecycle.currentState == Lifecycle.State.DESTROYED) {
      // ignore
      Timber.i("lifecycle countdown: lifecycle-state is destroyed")
      return
    }
    if (!lifecycleOwner.lifecycle.currentState.isAtLeast(Lifecycle.State.RESUMED)) {
      Timber.i("lifecycle countdown: lifecycle-state is not resumed yet")
      return
    }
    //cancel already pending timer if present
    cancel(false)
    //create and start timer
    countDownTimer = object : CountDownTimer(durationMillis, intervalMillis) {
      override fun onTick(millisUntilFinished: Long) {
        onIntervalTick(millisUntilFinished)
      }
      override fun onFinish() {
        onFinished()
      }
    }.start()
  }

  override fun cancel(callFinish: Boolean) {
    if (countDownTimer == null) return
    Timber.i("lifecycle countdown: canceled, callFinish: $callFinish")
    if (callFinish) {
      countDownTimer!!.onFinish()
    }
    countDownTimer!!.cancel()
    countDownTimer = null
  }

  @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
  fun pause() {
    lifecycleOwner.lifecycle.removeObserver(this)
    Timber.i("lifecycle countdown: stop called automatically")
    cancel(false)
  }

}