Kotlin: lag in coroutine runBlocking

Question

I am using kotlin Coroutines to perform async network operations to avoid NetworkOnMainThreadException . The problem is the lag that happens when i use runBlocking ,that take sometime to complete current thread.

How can i prevent this delay or lag,and allow the async operation to be done without delay

    runBlocking {
        val job = async (Dispatchers.IO) {
        try{
        //Network operations are here
        }catch(){

        }

     }

 }

Answer 1

By using runBlocking you are blocking the main thread until the coroutine finishes.

The NetworkOnMainThread exception is not thrown because technically the request is done on a background thread, but by making the main thread wait until the background thread is done, this is just as bad!

To fix this you could launch a coroutine, and any code that depends on the network request can be done inside the coroutine. This way code may still be executed on the main thread, but it never blocks.

// put this scope in your activity or fragment so you can cancel it in onDestroy()      
val scope = MainScope() 

// launch coroutine within scope
scope.launch(Dispachers.Main) {
    try {
        val result = withContext(Dispachters.IO) {
            // do blocking networking on IO thread
            ""
        }
        // now back on the main thread and we can use 'result'. But it never blocked!
    } catch(e: Exception) {
    }
}

---

If you don't care about the result and just want to run some code on a different thread, this can be simplified to:

GlobalScope.launch(Dispatchers.IO) {
    try {
        // code on io thread
    } catch(e: Exception) {
    }
}

Note: if you are using variables or methods from the enclosing class you should still use your own scope so it can be cancelled in time.