fcenesiz / service-types

Service types and usages

1. started-service

• Asynctask is deprecated!
• works on main thread

use this instead of asynctask on Java

ExecutorService executor = Executors.newSingleThreadExecutor();
Handler handler = new Handler(Looper.getMainLooper());

executor.execute(() -> { // doInBackground
    //Background work here
        
    handler.post(() -> { // onPostExecute
        //UI Thread work here
        
    });
});

or with kotlin coroutines

GlobalScope.launch {
    coroutineScope {
        // onPreExecute
        
        launch {
            // doInBackground
            delay(5000)
        }
    }
}

// also
GlobalScope.launch(Dispatchers.IO) {
   // doInBackground
   val answer = doNetworkCall()
   withContext(Dispatchers.Main){
        // main
        tvTitle.text = answer
   }
}

or with runOnUIThread()

Thread{
    // background 
    runOnUiThread { 
        // main
    }
}.start()

or with post() method

Thread{
    // background 
    someView.post {
        // main
    }
}.start()

or with handler

Thread{
    // background
    Handler(Looper.getMainLooper()).post {
        // main thread
    }
}.start()

or with handleMessage()

handler = object : Handler(Looper.getMainLooper()){
    override fun handleMessage(msg: Message) {
        checkBox.isChecked = (msg.data.getInt("sleep_time", 0) > 3)
    }
}

...

Thread{
    val message = Message.obtain()
    message.data = Bundle().apply {
        putInt("sleep_time", 5)
    }
    handler.sendMessage(message)
}.start()

2. intent-service (Deprecated!)

• sub-class of started-service
• has own worker thread (asynctask)
• need to override onHandleIntent()
• handles multi-threading details internally, creates a work queue for handle all intents
• automatically stops itself when work is complete (No need to use stopSelf() or stopService())
• running style: onStartCommand() -> work queue -> onHandleIntent()

started-service vs intent-service

• started-service

  • operates in main thread
  • may block the ui
  • used for short duration

• intent-service

  • operates in worker thread
  • does not block the ui
  • used for long process

3. bound-service

A bound service is the server in a client-server interface.

• returns data
• need to override bindService()
• works on main thread
• for long-standing connection
• onBind() returns IBinder
• If the calling component is destroyed then Bound Services too gets destroyed
• usage
  • Generally bindService() in onStart() and unBindService() in onStop()
  • If you want your Activity to bind to the service even when it is not visible, bindService() in onCreate() and unBindService() in onDestroy()