Answer by Santanu Sur for How to fix 'android.os.NetworkOnMainThreadException'?

You can use Kotlin-coroutines

 class YoutActivity : AppCompatActivity, CoroutineScope {

      override fun onCreate(...) {
         launch {  yourHeavyMethod() }
      }

      suspend fun yourHeavyMethod() {
         with(Dispatchers.IO){ yourNetworkCall() }
         ...
         ...
      }
 } 

You can follow this guide.