[android] What is the difference between an IntentService and a Service?

Can you please help me understand what the difference between an IntentService and a Service is?

service: It runs in the background on your system. For example,

1. If you went to a hotel and you give your order for a soup to a server
2. The server gets your order and sends to chef
3. You don't know how the soup is made in the kitchen and what processes are required for making the soup
4. Once your order is ready, the server brings you the soup.

background process: chef making soup

IntentService:- it's consecutive service.. (i.e) when you order many food items at a time to server but the server delivers those items one by one and not deliver them all at once.

Intent service is child of Service

IntentService: If you want to download a bunch of images at the start of opening your app. It's a one-time process and can clean itself up once everything is downloaded.

Service: A Service which will constantly be used to communicate between your app and back-end with web API calls. Even if it is finished with its current task, you still want it to be around a few minutes later, for more communication

Service runs actually in the same thread of your app; when you extends Service, you must manually spawn new threads to run CPU blocking operations.

vs

IntentService is a subclass of Service which spawns a thread to do background work from there(No need to create a new thread to do CPU blocking operations).

Service is a base class of service implementation. Service runs on the application's main thread which may reduce the application performance. Thus, IntentService, which is a direct subclass of Service is available to make things easier.

The IntentService is used to perform a certain task in the background. Once done, the instance of IntentService terminates itself automatically. Examples for its usage would be to download a certain resource from the Internet.

Differences

1. Service class uses the application's main thread, while IntentService creates a worker thread and uses that thread to run the service.
2. IntentService creates a queue that passes one intent at a time to onHandleIntent(). Thus, implementing a multi-thread should be made by extending Service class directly. Service class needs a manual stop using stopSelf(). Meanwhile, IntentService automatically stops itself when it finishes execution.
3. IntentService implements onBind() that returns null. This means that the IntentService can not be bound by default.
4. IntentService implements onStartCommand() that sends Intent to queue and to onHandleIntent().

In brief, there are only two things to do to use IntentService. Firstly, to implement the constructor. And secondly, to implement onHandleIntent(). For other callback methods, the super is needed to be called so that it can be tracked properly.

See Tejas Lagvankar's post about this subject. Below are some key differences between Service and IntentService and other components.

Service: Works in the main thread so it will cause an ANR (Android Not Responding) after a few seconds.

IntentService: Service with another background thread working separately to do something without interacting with the main thread.

Service

• Task with no UI,but should not use for long Task. Use Thread within service for long Task
• Invoke by onStartService()
• Triggered from any Thread
• Runs On Main Thread
• May block main(UI) thread

IntentService

• Long task usually no communication with main thread if communication is needed then it is done by Handler or broadcast
• Invoke via Intent
• triggered from Main Thread (Intent is received on main Thread and worker thread is spawned)
• Runs on separate thread
• We can't run task in parallel and multiple intents are Queued on the same worker thread.