Kotlin Flow

Activity

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding
    private val viewModel : MainViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        CoroutineScope(Dispatchers.Main).launch {
            viewModel.countDownTimerFlow.collect {
                binding.textViewCounter.text = it.toString()

            }
        }
    }
}

ViewModel

class MainViewModel : ViewModel() {

    init {
        collectInViewModel()
    }
    val countDownTimerFlow = flow<Int> {
        val countDownFrom = 10
        emit(countDownFrom)

        var counter = countDownFrom
        while (counter > 0) {
            delay(1000)
            counter--
            emit(counter)
        }
    }

    private fun collectInViewModel() {
        CoroutineScope(Dispatchers.Main).launch {
            countDownTimerFlow
                .filter { it % 3 == 0 }
                .map { it * it }
                .collect { println("Counter is $it") }

            /*
            countDownTimerFlow.collectLatest {
                // delay(2000)
                println("Counter is $it")
            }
            */
        }
    }
}