Service VS Intentservice in the Android Platform

Service vs IntentService in the Android platform

Tejas Lagvankar wrote a nice post about this subject.
Below are some key differences between Service and IntentService.

When to use?

• The Service can be used in tasks with no UI, but shouldn't be too long. If you need to perform long tasks, you must use threads within Service.

• The IntentService can be used in long tasks usually with no communication to Main Thread. If communication is required, can use Main Thread handler or broadcast intents. Another case of use is when callbacks are needed (Intent triggered tasks).

How to trigger?

• The Service is triggered by calling method startService().

• The IntentService is triggered using an Intent, it spawns a new worker thread and the method onHandleIntent() is called on this thread.

Triggered From

• The Service and IntentService may be triggered from any thread, activity or other application component.

Runs On

• The Service runs in background but it runs on the Main Thread of the application.

• The IntentService runs on a separate worker thread.

Limitations / Drawbacks

• The Service may block the Main Thread of the application.

• The IntentService cannot run tasks in parallel. Hence all the consecutive intents will go into the message queue for the worker thread and will execute sequentially.

When to stop?

• If you implement a Service, it is your responsibility to stop the service when its work is done, by calling stopSelf() or stopService(). (If you only want to provide binding, you don't need to implement this method).

• The IntentService stops the service after all start requests have been handled, so you never have to call stopSelf().

What is the difference between an IntentService and a Service?

In short, a Service is a broader implementation for the developer to set up background operations, while an IntentService is useful for "fire and forget" operations, taking care of background Thread creation and cleanup.

From the docs:

Service
A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use.

IntentService
Service is a base class for IntentService Services that handle asynchronous requests (expressed as Intents) on demand. Clients send requests through startService(Intent) calls; the service is started as needed, handles each Intent in turn using a worker thread, and stops itself when it runs out of work.

Refer this doc - http://developer.android.com/reference/android/app/IntentService.html

Differences in the use of IntentService and Service

Service

This is the base class for all services. When you extend this class, it’s important that you create a new thread in which to do all the service’s work, because the service uses your application’s main thread, by default, which could slow the performance of any activity your application is running.

IntentService

This is a subclass of Service that uses a worker thread to handle all start requests, one at a time. This is the best option if you don’t require that your service handle multiple requests simultaneously. All you need to do is implement onHandleIntent(), which receives the intent for each start request so you can do the background work.

Differences

Service class uses the application's main thread, while IntentService creates a worker thread and uses that thread to run the service. 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 there is no intent in queue. IntentService implements onBind() that returns null. This means that the IntentService can not be bound by default. IntentService implements onStartCommand() that sends Intent to queue and to onHandleIntent().

Service vs IntentService in a case of location tracking service

An IntentService is meant to be a fire and forget service, for relatively short tasks that may be repeated. Another important distinction is that an IntentService stops itself when onHandleIntent() returns. A regular Service doesn't stop unless you (or the android os) explicitly stop it.It sounds like you are planning on a long-running task that also runs when your app is not in the foreground.

In this scenario you definitely want to use a regular Service. You can still choose to perform the work in a separate thread by creating one inside the service and doing the work in there, but you don't necessarily have to. Remember that by default, a Service runs on the main thead.

Which one should we use between Service, intentservice, runnable and thread?

Check out the following post

When to use?

The Service can be used in tasks with no UI, but shouldn't be too long. If you need to perform long tasks, you must use threads within Service.

The IntentService can be used in long tasks usually with no communication to Main Thread. If communication is required, can use Main Thread handler or broadcast intents. Another case of use is when callbacks are needed (Intent triggered tasks).

How to trigger?

The Service is triggered by calling method startService().

The IntentService is triggered using an Intent, it spawns a new worker thread and the method onHandleIntent() is called on this thread.

Triggered From

The Service and IntentService may be triggered from any thread, activity or other application component.

Runs On

The Service runs in background but it runs on the Main Thread of the application.

The IntentService runs on a separate worker thread.

Limitations / Drawbacks

The Service may block the Main Thread of the application.

The IntentService cannot run tasks in parallel. Hence all the consecutive intents will go into the message queue for the worker thread and will execute sequentially.

When to stop?

If you implement a Service, it is your responsibility to stop the service when its work is done, by calling stopSelf() or stopService(). (If you only want to provide binding, you don't need to implement this method).

The IntentService stops the service after all start requests have been handled, so you never have to call stopSelf().

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