class Foo {
    private val scope = CoroutineScope(SupervisedJob() + Dispatchers.Main.immediate)

    fun init() {
        println("a")

        scope.launch {
            println("b")

            flowOf("hello")
                .collect {
                    println("c")
                }
        }

        println("d")
    }
}

a, b, c, d

a, d, b, c

Dispatchers.Main

Dispatchers.Main.immediate

Dispatchers.main

Dispatchers.Main.immediate

withContext(Dispatchers.Main) {
    println("a") // may be in next event loop
}
withContext(DIspatchers.Main.immediate) {
    println("b") // in the same event loop, if current thread is main UI thread
}

launch()

Returns dispatcher that executes coroutines immediately

launch

b

d

c

2021-09-28 15:36:20.409 27971-27971/I/System.out: Coroutines: a
2021-09-28 15:36:20.413 27971-27971/I/System.out: Coroutines: b
2021-09-28 15:36:20.414 27971-27971/I/System.out: Coroutines: c
2021-09-28 15:36:20.414 27971-27971/I/System.out: Coroutines: d

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)
        scope.launch {
            fetchUri()
            init()
        }
    }

    suspend fun fetchUri() = withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
        delay(100)
    }

    private fun init() {
        val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)
        println("Coroutines: ${Thread.currentThread()}: a")
        scope.launch {
            println("Coroutines: ${Thread.currentThread()}: b")
            flowOf("hello")
                .collect {
                    println("Coroutines: ${Thread.currentThread()}: c")
                }
        }
        println("Coroutines: ${Thread.currentThread()}: d")
    }
}

2021-09-28 22:30:56.895 16765-16765/I/System.out: Coroutines: Thread[main,5,main]: a
2021-09-28 22:30:56.897 16765-16765/I/System.out: Coroutines: Thread[main,5,main]: b
2021-09-28 22:30:56.905 16765-16765/I/System.out: Coroutines: Thread[main,5,main]: c
2021-09-28 22:30:56.906 16765-16765/I/System.out: Coroutines: Thread[main,5,main]: d

class Activity {
    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)

    fun onCreate() {
        scope.launch {
        	delay(1000)
            val viewModel = FooViewModel(..)
            viewModel.init()
        }
    }
}

fetchUri()

launch(start = UNDISPATCHED)

launch()

drop(1)