Service vs IntentService in the Android platform

Question

I am seeking an example of something that can be done with an IntentService that cannot be done with a Service  and vice-versa    I also believe that an IntentService runs in a different thread and a Service does not   So  as far as I can see  starting a service within its own thread is like starting an IntentService   Is that correct

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The Major Difference between a Service and an IntentService is described as follows   Service    1 A Service by default  runs on the application s main thread  here no default worker thread is available  So the user needs to create a separate thread and do the required work in that thread   2 Allows Multiple requests at a time  Multi Threading   IntentService    1 Now  coming to IntentService  here a default worker thread is available to perform any operation  Note that - You need to implement onHandleIntent   method  which receives the intent for each start request  where you can do the background work   2 But it allows only one request at a time

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If someone can show me an example of something that can be done with an IntentService and can not be done with a Service and the other way around    By definition  that is impossible  IntentService is a subclass of Service  written in Java  Hence  anything an IntentService does  a Service could do  by including the relevant bits of code that IntentService uses      Starting a service with its own thread is like starting an IntentService  Is it not    The three primary features of an IntentService are    the background thread the automatic queuing of Intents delivered to onStartCommand    so if one Intent is being processed by onHandleIntent   on the background thread  other commands queue up waiting their turn the automatic shutdown of the IntentService  via a call to stopSelf    once the queue is empty   Any and all of that could be implemented by a Service without extending IntentService

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I m sure you can find an extensive list of differences by simply googling something such as  Android IntentService vs Service    One of the more important differences per example is that IntentService ends itself once it s done    Some examples  quickly made up  could be    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

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An IntentService is an extension of a Service that is made to ease the execution of a task that needs to be executed in background and in a seperated thread   IntentService starts  create a thread and runs its task in the thread  once done  it cleans everything  Only one instance of a IntentService can run at the same time  several calls are enqueued   It is very simple to use and very convenient for a lot of uses  for instance downloading stuff  But it has limitations that can make you want to use instead the more basic  not simple  Service   For example  a service connected to a xmpp server and bound by activities cannot be simply done using an IntentService  You ll end up ignoring or overriding IntentService stuffs

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IntentService  IntentService runs on its own thread   It will stop itself when it s done  More like fire and forget  Subsequent calls will be queued  Good for queuing calls  You can also spin multiple threads within IntentServiceif you need to- You can achieve this using ThreadPoolExecutor   I say this because many people asked me  why use IntentService since it doesn t support parallel execution   IntentService is just a thread  You can do whatever you need inside it- Even spinning multiple threads  The only caveat is that IntentService finishes as soon as you spin those multiple threads  It doesn t wait for those threads to come back  You need to take care of this  So I recommend using ThreadPoolExecutor in those scenarios    Good for Syncing  uploading etc       Service  By Default Service runs on the main thread  You need to spin a worker thread to do your job   You need to stop service explicitly  I used it for a situation when you need to run stuff in the background even when you move away from your app and come back more for a Headless service    Again you can run multiple threads if you need to   Can be used for apps like music players    You can always communicate back to your activity using  BroadcastReceivers if you need to

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Don t reinvent the wheel  IntentService extends Service class which clearly means that IntentService is intentionally made for same purpose    So what is the purpose     IntentService s purpose is to make our job easier to run background tasks without even worrying about   Creation of worker thread Queuing the processing multiple-request one by one  Threading  Destroying the Service   So NO  Service can do any task which an IntentService would do  If your requirements fall under the above-mentioned criteria  then you don t have to write those logics in the Service class  So don t reinvent the wheel because IntentService is the invented wheel   The  Main  difference     The Service runs on the UI thread while an IntentService runs on a   separate thread   When do you use IntentService   When you want to perform multiple background tasks one by one which exists beyond the scope of an Activity then the IntentService is perfect   How IntentService is made from Service  A normal service runs on the UI Thread Any Android Component type runs on UI thread by default eg Activity  BroadcastReceiver  ContentProvider and Service   If you have to do some work that may take a while to complete then you have to create a thread  In the case of multiple requests  you will have to deal with synchronization  IntentService is given some default implementation which does those tasks for you  According to developer page   IntentService creates a Worker Thread IntentService creates a Work Queue which sends request to onHandleIntent   method one by one  When there is no work then IntentService calls stopSelf   method Provides default implementation for onBind   method which is null Default implementation for onStartCommand   which sends Intent request to WorkQueue and eventually to onHandleIntent

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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

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Service   Invoke by startService   Triggered from any Thread Runs on Main Thread May block main  UI  thread  Always use thread within service for long task Once task has done  it is our responsibility to stop service by calling stopSelf   or stopService     IntentService   It performs long task usually no communication with main thread if communication is needed then it is done by Handler or BroadcastReceiver Invoke via Intent Triggered from Main Thread Runs on the separate thread Can t run the task in parallel and multiple intents are Queued on the same worker thread

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Adding points to the accepted answer   See the usage of IntentService within Android API  eg   public class SimpleWakefulService extends IntentService       public SimpleWakefulService             super  SimpleWakefulService                Override     protected void onHandleIntent Intent intent            To create an IntentService component for your app  define a class that extends IntentService  and within it  define a method that overrides onHandleIntent      Also  see the source code of the IntentService  it s constructor and life cycle methods like onStartCommand        Override     public int More    onStartCommand Intent intent  int flags  int startId           onStart intent  startId           return mRedelivery   START REDELIVER INTENT   START NOT STICKY             Service together an AsyncTask is one of best approaches for many   use cases where the payload is not huge    or just create a class   extending IntentSerivce  From Android version 4 0 all network   operations should be in background process otherwise the application compile build fails    separate thread from the UI  The AsyncTask class provides one of the simplest ways to fire off a new task from the UI thread  For more discussion of this topic  see the blog post   from Android developers guide   IntentService is a base class for 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      Design pattern used in IntentService     This  work queue processor  pattern is commonly used to offload tasks from an application s main thread  The IntentService class exists to simplify this pattern and take care of the mechanics  To use it  extend IntentService and implement onHandleIntent Intent   IntentService will receive the Intents  launch a worker thread  and stop the service as appropriate   All requests are handled on a single worker thread -- they may take as long as necessary  and will not block the application s main loop   but only one request will be processed at a time   The IntentService class provides a straightforward structure for running an operation on a single background thread  This allows it to handle long-running operations without affecting your user interface s responsiveness  Also  an IntentService isn t affected by most user interface lifecycle events  so it continues to run in circumstances that would shut down an AsyncTask   An IntentService has a few limitations   It can t interact directly with your user interface  To put its results in the UI  you have to send them to an Activity  Work requests run sequentially  If an operation is running in an IntentService  and you send it another request  the request waits until the first operation is finished  An operation running on an IntentService can t be interrupted  However  in most cases     IntentService is the preferred way to simple background operations          Volley Library   There is the library called volley-library for developing android networking applications The source code is available for the public in GitHub   The android official documentation for  Best practices for Background jobs  helps better understand on intent service  thread  handler  service  and also Performing Network Operations

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Android IntentService vs Service  1 Service    A Service is invoked using startService    A Service can be invoked from any thread  A Service runs background operations on the Main Thread of the Application by default  Hence it can block your Application   s UI  A Service invoked multiple times would create multiple instances  A service needs to be stopped using stopSelf   or stopService    Android service can run parallel operations    2  IntentService    An IntentService is invoked using Intent  An IntentService can in invoked from the Main thread only  An IntentService creates a separate worker thread to run background operations  An IntentService invoked multiple times won   t create multiple instances  An IntentService automatically stops after the queue is completed  No need to trigger stopService   or stopSelf    In an IntentService  multiple intent calls are automatically Queued and they would be executed sequentially  An IntentService cannot run parallel operation like a Service    Refer from Here

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If someone can show me an example of something that you can be done with an IntentService and can not be done with a service and the other way around    IntentService can not be used for Long Time Listening  Like for XMPP Listeners  its a single time operator  do the job and wave goodbye   Also it has just one threadworker  but with a trick  you can use it as unlimited

[android] Service vs IntentService in the Android platform

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