Every time my app starts, I need to call 2-3 URL endpoints to get the latest data from the API. Every app encounters this scenario one way or another. I need to know when each API call finishes so that I can prompt the user a Snackbar or dialog to indicate that I already got the latest data. And more importantly, I made sure that calling the function 2-3 times won’t block the main thread.

Here’s how I implemented it using Kotlin’s Coroutines.

My function structure looks like the one below. This function performs an HTTP GET from the API and saves it into a local database.

private suspend fun getDataFromAPI(url: String) = coroutineScope {
    // More code
}

And this is how I called it using Coroutines.

CoroutineScope(Dispatchers.IO).launch {
    val asyncData1 = async {
        getDataFromAPI("https://someurl.com/api/data1")
    }
    val asyncData2 = async {
        getDataFromAPI("https://someurl.com/api/data2")
    }
    val asyncData3 = async {
        getDataFromAPI("https://someurl.com/api/data3")
    }
    if (asyncData1.await().join().responseMessage.isNotEmpty() &&
        asyncData2.await().join().responseMessage.isNotEmpty() &&
        asyncData3.await().join().responseMessage.isNotEmpty()
                    ) {
        // Display Snabackbar or dialog here
    }
}

Important to take note here is the join() function which will wait for the completion of our async call.