Running Asynchronous Tasks in Android Using Coroutines

AsyncWithCoroutines.kt

/**
This example demonstrates how to perform background work in Android using Coroutines.
**/
class AsyncWithCoroutines {

    private val scope = CoroutineScope(Dispatchers.Default)

    companion object {
        const val TAG = "AsyncWithCoroutines"
    }

    fun runAsyncTask() {
        Log.d(TAG, "usingCoroutines: Coroutine start!")

        scope.launch {
            val result = runBackgroundTask()
            Log.d(TAG, "usingCoroutines: $result")
        }

        Log.d(TAG, "usingCoroutines: Coroutine end!")
    }

    private suspend fun runBackgroundTask(): String {
        delay(5000)  // simulate background work
        return "Task Completed"
    }
}

flow.txt

                     ┌───────────────────────────────┐
                     │     runAsyncTask() (MAIN)     │
                     └───────────────────────────────┘
                                      │
                                      │ launches coroutine
                                      ▼
            ┌──────────────────────────────────────────────────┐
            │   scope.launch { ... } running on                |
            |    Dispatchers.Default                           |
            └──────────────────────────────────────────────────┘
                                      │
                                      │ suspend runBackgroundTask()
                                      ▼
                     ┌───────────────────────────────┐
                     │    delay(5000) suspends       | 
                     |    coroutine                  | 
                     └───────────────────────────────┘
                                      │
                                      │ After delay resumes on same dispatcher
                                      ▼
                     ┌───────────────────────────────┐
                     │ return "Task Completed"       │
                     └───────────────────────────────┘
                                      │
                                      ▼
            ┌──────────────────────────────────────────────────┐
            │  Coroutine resumes and logs result (Background)  │
            └──────────────────────────────────────────────────┘

output.txt

usingCoroutines: Coroutine start!
usingCoroutines: Coroutine end!
-- 5 seconds later --
usingCoroutines: Task Completed