Vignesh Prabhu
Vignesh Prabhu

Vignesh Prabhu

Coroutines Scopes

Coroutines Scopes

Vignesh Prabhu's photo
Vignesh Prabhu
·May 30, 2021·

2 min read

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What is Coroutine scope ?

  • Coroutine scope is a constraint in which coroutines are executed
  • In Android , these scopes also define the lifespan of the coroutines they embrace.

There are 3 types of Coroutine scopes

  • GlobalScope
  • LifeCycleScope
  • ViewModelScope

GlobalScope

  • The coroutines launched in this scope live long as the application does
  • If the coroutines finishes the job , then it is destroyed and will not kept alive as long as application does

Code

/**
* globalscope
*/
// print Main thread name
Log.d("Coroutines", "Main  ${Thread.currentThread().name.toString()}")
GlobalScope.launch {
   // run this coroutine till application is killed .
   while (true){
   // delay for 2 seonds
   delay(2000)
   // print thread name
   Log.d("Coroutines", "GlobalScope  ${Thread.currentThread().name.toString()}")
   }
}
Log.d("Coroutines", "End of GlobalScope ")

Output

17:03:32.552 D/Coroutines: Main  main
17:03:32.596 D/Coroutines: End of GlobalScope 
17:03:34.607 D/Coroutines: GlobalScope  DefaultDispatcher-worker-1
17:03:36.609 D/Coroutines: GlobalScope  DefaultDispatcher-worker-1
17:03:38.610 D/Coroutines: GlobalScope  DefaultDispatcher-worker-1
17:03:39.716 D/Coroutines: onStop
17:03:39.720 D/Coroutines: onDestroy
17:03:40.615 D/Coroutines: GlobalScope  DefaultDispatcher-worker-1

LifecycleScope

  • The coroutines launched in this scope live long as the activity or fragment in which the lifeCycleScope is launched

Code

/**
* lifecyclescope
*/
// print Main thread name
Log.d("Coroutines", "Main  ${Thread.currentThread().name.toString()}")
lifecycleScope.launch(Dispatchers.IO){
  // run this coroutine till activity is killed .
  while (true){
      // delay for 2 seconds
      delay(2000)
      // print thread name
     Log.d("Coroutines", "lifecycleScope  ${Thread.currentThread().name.toString()}")
   }
}
Log.d("Coroutines", "End of lifecycleScope )

Output

17:10:24.446 D/Coroutines: Main  main
17:10:24.499 D/Coroutines: End of lifecycleScope 
17:10:26.517 D/Coroutines: lifecycleScope  DefaultDispatcher-worker-1
17:10:28.519 D/Coroutines: lifecycleScope  DefaultDispatcher-worker-1
17:10:30.488 D/Coroutines: onStop
17:10:30.504 D/Coroutines: onDestroy

ViewModelScope

  • The coroutine launched in this cope live long as the viewmodel is alive

Please leave your comments to improve.

Happy Coding

 
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