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I am looking for what service should be used in android applicaton.
Docs says
A Service is an application component that can perform long-running operations in the background and does not provide a user interface.
I have read this thread Application threads vs Service threads that saying same services are for running operation in background.
But here this can be done using Thread also. Any difference between them and where you should use them
UPDATE based on latest documentation:
Android has included in its documentation on when you should use Service vs Thread. Here is what it says:
If you need to perform work outside your main thread, but only while
the user is interacting with your application, then you should
probably instead create a new thread and not a service. For example,
if you want to play some music, but only while your activity is
running, you might create a thread in onCreate(), start running it in
onStart(), then stop it in onStop(). Also consider using AsyncTask or
HandlerThread, instead of the traditional Thread class. See the
Processes and Threading document for more information about threads.
Remember that if you do use a service, it still runs in your
application's main thread by default, so you should still create a new
thread within the service if it performs intensive or blocking
operations.
Another notable difference between these two approaches is that Thread will sleep if your device sleeps. Whereas, Service can perform operation even if the device goes to sleep. Let's take for example playing music using both approaches.
Thread Approach: the music will only play if your app is active or screen display is on.
Service Approach: the music can still play even if you minimized your app or screen is off.
Note: Starting API Level 23, you should Test your app with Doze.
Android Documentation - Services
A Service is meant to run your task independently of the Activity, it allows you to run any task in background. This run on the main UI thread so when you want to perform any network or heavy load operation then you have to use the Thread there.
Example : Suppose you want to take backup of your instant messages daily in the background then here you would use the Service.
Threads is for run your task in its own thread instead of main UI thread. You would use when you want to do some heavy network operation like sending bytes to the server continuously, and it is associated with the Android components. When your component destroy who started this then you should have stop it also.
Example : You are using the Thread in the Activity for some purpose, it is good practice to stop it when your activity destroy.
This is the principle i largely follow
Use a Thread when
app is required to be visible when the operation occurs.
background operation is relatively short running (less than a minute or two)
the activity/screen/app is highly coupled with the background operation, the user usually 'waits' for this operation to finish before doing anything else in the app.
Using a thread in these cases leads to cleaner, more readable & maintainable code. That being said its possible to use a Service( or IntentService).
Use a Service when
app could be invisible when the operation occurs (Features like Foreground service could help with operations being interrupted)
User is not required to 'wait' for the operation to finish to do other things in the app.
app is visible and the operation is independent of the app/screen context.
Reference from https://developer.android.com/guide/components/services.html
A service is simply a component that can run in the background even when the user is not interacting with your application. Thus, you should create a service only if that is what you need.
If you need to perform work outside your main thread, but only while the user is interacting with your application, then you should probably instead create a new thread and not a service.
For example, if you want to play some music, but only while your activity is running, you might create a thread in onCreate(), start running it in onStart(), then stop it in onStop().
Remember that if you do use a service, it still runs in your application's main thread by default, so you should still create a new thread within the service if it performs intensive or blocking operations.
My Approach for explanation is simple:
Create a thread when you are in the activity and want to do some background operation with frequent communication with the main thread.
Alert- Don't create too many threads as 1 thread is equal to 1 processor thread. If you want to do parallel processing with threads(multiple) try your hands on Executors
Now you want long running operations with less interaction with UI then go for Service. Keep in mind service runs on UI thread. But now you want the processing should be done in background thread, then go for Intent Service.Intent service maintains their Thread Pools and do not create new threads and runs your tasks serially.
I have been reading around on internet connectivity with Android and noticed there are different ways to handle this i.e. AsyncTask and IntentService. However, I'm still not sure which one to use. My application is basically a location/trails finder with Google Maps. My internet connectivity will be used to find the nearest trails within a certain radius of the map. So, every time a user moves or swipes the map to a new location then it will update with the nearest trails. It will also add a new trail, and allow the user to rate a trail.
Will AsyncTask suffice for this or should I use IntentService?
They can be used very differently for different purposes.
AsyncTask is a handy threading utility that can be used if you need to constantly tell the user something or periodically perform operations on the main thread. It offers a lot of fine-grain control, and because of it's nature is very easy to work with in the Activity whereas an IntentService generally requires using the BroadcastReceiver or IBinder framework.
IntentService can be used very much like an AsyncTask, but it's purpose is meant for background downloading, uploading, or other blocking operations that don't need user interaction or main thread. For example, if you want to download and cache maps, you may want to call an IntentService so the user doesn't have to be looking at the app for it to download. Likewise, if you're sending data to your server, an IntentService is extremely helpful in this regard because you can start and forget. The user can, say, type a comment in your app then press "send". "Send" will launch the IntentService which gets the comment and send it off in to your server on a background thread. The user could press "send" and leave the app immediately and the comment will, eventually, still reach your servers (assuming no errors of course). If you did this with an AsyncTask in your Activity on the other hand, the system could kill off your process in the middle of your exchange and it may-or-may not go through.
Generally speaking, neither are meant for long running applications. They're meant for short, one-off operations. They could be used for permanent, or long-running actions but it's not recommended.
You should use an AsyncTask for short repetitive tasks that are tightly bound to an activity, like what you're currently trying to do. IntentService are more geared towards scheduled tasks (repetitive or not) that should run on the background, independent of your activity.
AsyncTask doesn't play well with configuration changes or other things that restart the Activity.
IntentService is good for a something that should always be available, regardless of how long it takes to do its work. I prefer IntentService in most cases because AsyncTask is so much more dependent on Activity state.
Some notes:
AsyncTask is best for quick tasks that should go right back to the UI, but it can be used in a variety of situations.
The statement "periodically perform operations on the main thread" is vague. AsyncTask spawns a new background thread that is different from the main thread, and does its work on the new thread. Thus the name AsyncTask.
An IntentService doesn't require "manipulating" the BroadcastReceiver framework. All you need to do is send a local broadcast Intent, and detect it in your Activity. Whether this is harder to do than an AsyncTask, I don't know.
IntentService is meant to do long-running tasks, which it does in the background.
AsyncTaskLoader is OK to use, but it's meant to be the base class for CursorLoader, etc.
If you want to refresh "nearby" trails when users move to a new location, an IntentService is probably better.
Don't forget to check for connectivity before trying to update location.
AsyncTasks are very tightly bound to Activitys and can often cause leaked window errors if you navigate away from the Activity that created the AsyncTask. But they are great for showing a ProgressBar because you can quickly update the progress percentage.
IntentServices are cleaner and safer. They are more difficult to implement when you are a beginner Android developer, but once you learn how to start them and handle them you will probably never go back to AsyncTasks!
IntentServices also allow for a more modular design in your app. I typically create a separate class for all my IntentServices, but for AsyncTasks I create them as an Activity inner class. If I were to separate out an AsyncTask from an Activity, I would have to pass in the Activity Context and View objects in the AsyncTask constructor which can be messy.
As mentioned above AsyncTask will solve your problem.
But Keep in mind that AsyncTask has an important weakness: it doesn't handle well Activity
"refresh" (eg during rotation). It may be a problem if, e.g., user rotate the phone while your AsyncTask is still loading stuff. If this is indeed a problem for you I recommend AsyncTaskLoader:
http://developer.android.com/reference/android/content/AsyncTaskLoader.html
AsyncTask and IntentService have many same
Can execute task in worker thread
Can run in background
Keep running till task finished event the activity which started it is destroyed
Can notify to update UI during task running or after task finish
For AsyncTask we often use onProgressUpdate, onPostExecute or if you want you can use BroadcastReceiver
For IntentService we use BroadcastReceiver
Different
1) Send task while running or after running finish
Example we have a task is: download file from server base on fileName.
Using AsyncTask
If we one instance of AsyncTask, during execute downloading file A we cannot execute download file B AsyncTask (since we get java.lang.IllegalStateException: Cannot execute task: the task is already running.). Also after downloading file A finished, we can not execute download file B (since we get java.lang.IllegalStateException: Cannot execute task: the task has already been executed (a task can be executed only once).
To download file B during or after download file A, we need to create new instance of AsyncTask.
=> To download file A and file B, we need 2 instance of AsyncTask => 2 worker thread created
Using IntentService
During download file A, we can sent intent to download file B => after download file A finished it will auto start download file B => don't need new instance, don't need new worker thread.
If we sent intent to download file B after download file A finished? After download file A finished, IntentSevice will destroyed (because there is no more task). Therefore, when start download file B, new instance of Service is created however no new thread created (service keep using only 1 worker thread which name is defined in IntentSevice constructor
2) Implement AsyncTask is easier than IntentService
USING
We will see that AsyncTask and IntentService have many same so in most case we can use AsyncTask or IntentService. However
I often use AsyncTask for some task that start, finish, interact with UI in 1 Activity
I often use IntentService for some task that can start/finish and interact or don't interact with UI from any Activity
This answer is base on my test. Please correct me if I am wrong. Hope it help.
In short, AsyncTask is meant for short tasks that have to communicate with main thread. IntentService is meant for long tasks that don't have to communicate with main thread.
For more info, check these links
http://www.onsandroid.com/2011/12/difference-between-android.html
https://medium.com/#skidanolegs/asynctask-vs-intentservice-1-example-without-code-5250bea6bdae
https://android.jlelse.eu/using-intentservice-vs-asynctask-in-android-2fec1b853ff4
I agree with #DeeV and #ebarrenechea about Intent service in part that you should use it for task that are not tight bound with Activity like uploading some data to server or storing data from server to database.
But starting from Android 3.0 there were introduced Loaders API Which should replace AsyncTask. So for example for loading list which you should display in Activity is better to use Loader which is designed to handle well all the configuration changes and Activity Life-cycle.
Vogella loader tutorial
I am editing the code of an android app that is making GPS calls in a service. LocationListener. It also uses ServiceConnection
In some views the device decides that my application is taking too long to respond, and that the user can either "Force Close" or "Wait". Before this popup appears, the application is still usable by the user, they can scroll, slide, press buttons etc.
I am only assuming this is related to the GPS service as it is running whenever this problem happens.
I heard that this problem has to do with a thread running on the UIthread, instead of a background thread. But I was sure that services run asynchronously in the background thread.
Insight appreciated
Using a service does not necessarily spawn a new thread, the service call runs on it's caller thread. From the android API Service doc at:
"Note that services, like other application objects, run in the main thread of their hosting process..".
You can specify the service to run on a different process but best practice is to spawn a new thread in the service.
More on android service at:
http://developer.android.com/reference/android/app/Service.html
I fully recommend you to extend AsyncTask,it enables proper and easy use of the UI thread. Allows you to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers. You may want to do all the computing in doInBackground method.BTW Force Close or Wait is a classic behavior for this kind of issues.
Good Luck!!!
Processing in a service can still cause your application to hang.
The solution you should be looking at implementing is to run any logic that may bog down your activity in a separate thread. This includes things like: Database updates/insertions, Network communication, and any other pieces of long running code.
The AsyncTask is a convenient method for this as you can manipulate the UI in the onPreExecute and the onPostExecute functions.
You can implement an AsyncTask directly in your service as a subclass.
Hoepfully this helps!
Cheers
Why do I read in the answer to most questions here a lot about AsyncTask and Loaders but nothing about Services? Are Services just not known very well or are they deprecated or have some bad attributes or something? What are the differences?
(By the way, I know that there are other threads about it, but none really states clear differences that help a developer to easily decide if he is better off using the one or the other for an actual problem.)
In some cases it is possible to accomplish the same task with either an AsyncTask or a Service however usually one is better suited to a task than the other.
AsyncTasks are designed for once-off time-consuming tasks that cannot be run of the UI thread. A common example is fetching/processing data when a button is pressed.
Services are designed to be continually running in the background. In the example above of fetching data when a button is pressed, you could start a service, let it fetch the data, and then stop it, but this is inefficient. It is far faster to use an AsyncTask that will run once, return the data, and be done.
If you need to be continually doing something in the background, though, a Service is your best bet. Examples of this include playing music, continually checking for new data, etc.
Also, as Sherif already said, services do not necessarily run off of the UI thread.
For the most part, Services are for when you want to run code even when your application's Activity isn't open. AsyncTasks are designed to make executing code off of the UI thread incredibly simple.
Services are completely different: Services are not threads!
Your Activity binds to a service and the service contains some functions that when called, blocks the calling thread. Your service might be used to change temperature from Celsius to Degrees. Any activity that binds can get this service.
However AsyncTask is a Thread that does some work in the background and at the same time has the ability to report results back to the calling thread.
Just a thought: A service may have a AsyncTask object!
Service is one of the components of the Android framework, which does not require UI to execute, which mean even when the app is not actively used by the user, you can perform some operation with service. That doesn't mean service will run in a separate thread, but it runs in main thread and operation can be performed in a separate thread when needed.
Examples usages are playing music in background, syncing data with server in backgroud without user interaction etc
AsyncTask on other hand is used for UI blocking tasks to be performed on a separate thread. It is same like creating a new thread and doing the task when all the tasks of creating and maintaining the threads and send back result to main thread are taken care by the AsyncTask
Example usage are fetching data from server, CRUD operations on content resolver etc
Service and asynctasks are almost doing the same thing,almost.using service or a asynctask depends on what is your requirement is.
as a example if you want to load data to a listview from a server after hitting some button or changing screen you better go with a asynctask.it runs parallel with main ui thread (runs in background).for run asynctack activity or your app should on main UI thread.after exit from the app there is no asynctask.
But services are not like that, once you start a service it can run after you exit from the app, unless you are stop the service.like i said it depends on your requirement.if you want to keep checking data receiving or check network state continuously you better go with service.
happy coding.
In few cases, you can achieve same functionality using both. Unlike Async Task, service has it's own life cycle and inherits Context (Service is more robust than an Async Task). Service can run even if you have exited the app. If you want to do something even after app closing and also need the context variable, you will go for Service.
Example: If you want to play a music and you don't want to pause if user leaves the app, you will definitely go for Service.
Comparison of a local, in-process, base class Service✱ to an AsyncTask:
✱ (This answer does not address exported services, or any service that runs in a process different from that of the client, since the expected use cases differ substantially from those of an AsyncTask. Also, in the interest of brevity, the nature of certain specialized Service subclasses (e.g., IntentService, JobService) will be ignored here.)
Process Lifetime
A Service represents, to the OS, "an application's desire to perform a longer-running operation while not interacting with the user" [ref].
While you have a Service running, Android understands that you don't want your process to be killed. This is also true whenever you have an Activity onscreen, and it is especially true when you are running a foreground service. (When all your application components go away, Android thinks, "Oh, now is a good time to kill this app, so I can free up resources".)
Also, depending on the last return value from Service.onCreate(), Android can attempt to "revive" apps/services that were killed due to resource pressure [ref].
AsyncTasks don't do any of that. It doesn't matter how many background threads you have running, or how hard they are working: Android will not keep your app alive just because your app is using the CPU. It has to have some way of knowing that your app still has work to do; that's why Services are registered with the OS, and AsyncTasks aren't.
Multithreading
AsyncTasks are all about creating a background thread on which to do work, and then presenting the result of that work to the UI thread in a threadsafe manner.
Each new AsyncTask execution generally results in more concurrency (more threads), subject to the limitations of the AsyncTasks's thread-pool [ref].
Service methods, on the other hand, are always invoked on the UI thread [ref]. This applies to onCreate(), onStartCommand(), onDestroy(), onServiceConnected(), etc. So, in some sense, Services don't "run" in the background. Once they start up (onCreate()), they just kinda "sit" there -- until it's time to clean up, execute an onStartCommand(), etc.
In other words, adding additional Services does not result in more concurrency. Service methods are not a good place to do large amounts of work, because they run on the UI thread.
Of course, you can extend Service, add your own methods, and call them from any thread you want. But if you do that, the responsibility for thread safety lies with you -- not the framework.
If you want to add a background thread (or some other sort of worker) to your Service, you are free to do so. You could start a background thread/AsyncTask in Service.onCreate(), for example. But not all use cases require this. For example:
You may wish to keep a Service running so you can continue getting location updates in the "background" (meaning, without necessarily having any Activities onscreen).
Or, you may want to keep your app alive just so you can keep an "implicit" BroadcastReceiver registered on a long-term basis (after API 26, you can't always do this via the manifest, so you have to register at runtime instead [ref]).
Neither of these use cases require a great deal of CPU activity; they just require that the app not be killed.
As Workers
Services are not task-oriented. They are not set up to "perform a task" and "deliver a result", like AsyncTasks are. Services do not solve any thread-safety problems (notwithstanding the fact that all methods execute on a single thread). AsyncTasks, on the other hand, handle that complexity for you.
Note that AsyncTask is slated for deprecation. But that doesn't mean your should replace your AsyncTasks with Services! (If you have learned anything from this answer, that much should be clear.)
TL;DR
Services are mostly there to "exist". They are like an off-screen Activity, providing a reason for the app to stay alive, while other components take care of doing the "work". AsyncTasks do "work", but they will not, in and of themselves, keep a process alive.
What is the difference between Service, Async Task & Thread. If i am not wrong all of them are used to do some stuff in background. So, how to decide which to use and when?
Probably you already read the documentation description about them, I won't repeat them, instead I will try to give answer with my own words, hope they will help you.
Service is like an Activity but has no user interface. Probably if you want to fetch the weather for example you won't create a blank activity for it, for this you will use a Service.
A Thread is a Thread, probably you already know it from other part. You need to know that you cannot update UI from a Thread. You need to use a Handler for this, but read further.
An AsyncTask is an intelligent Thread that is advised to be used. Intelligent as it can help with it's methods, and there are three methods that run on UI thread, which is good to update UI components.
I am using Services, AsyncTasks frequently. Thread less, or not at all, as I can do almost everything with AsyncTask.
This is the easiest answer for your question
Thread
is an unit of execution who run "parallel" to the Main Thread is an important point, you can't update a UI component from the any thread here except main thread.
AsyncTask
is a special thread, which gives you helper methods to update UI so basically you can update the UI even AsyncTask will run on a background thread. Interprocess communication handling is not required to be done explicitly.
Service
solve the above problem because it live separate from the activity that invoke it so it can continue running even when the activity is destroyed, it run in the Main Thread(beware of ANR) use a background service (extend IntentService it create the worker thread automatically for you). Service is like an activity without UI,
is good for long task
Few more information I wish someone had told me a few days ago:
You can share global variables - such as threads - between Activities and Services.
Your application together with all its global variables will not be wiped out as long as there is an Activity or a Service still present.
If you have an instance of a Service in your app and the OS needs resources, it first kills your Activities, but as long as there is the Service, the OS won't wipe out your application together with its global variables.
My use case is like this: I have one thread in global space that is connected to a server and an Activity that shows the results. When user presses the home button, the Activity goes to background and a new Service is started. This service then reads results from the thread and displays information in the notification area when needed. I don't worry about the OS destroying my Activity because I know that as long as the Service is running it won'd destroy the thread.
In short, Service for time consuming tasks, AsyncTask for short-lived tasks, Thread is a standard java construction for threads.
From developer's perspective:
Thread: Used to execute the set to codes parallely to the main thread. But you cannot handle the UI inside the thread. For that you need to use Handler. Hadler binds thread Runnable with Looper that makes it a UI thread.
ASyncTask: Used for handling those tasks that you cannot make to work on the main thread. For example, an HTTP request is a very heavy work that cannot be handled on the main thread, so you handle the HTTP request in the ASyncTask It works parallelly with your main thread Asynchronously in the background. It has a few callback methods that are invoked on their corresponding events.
Service: Works in the background under the same Application process. It is implemented when you have to do some processing that doesn't have any UI associated with it.
service is like activity long time consuming task but Async task allows us to perform long/background operations and show its result on the UI thread without having to manipulate threads.