Develop Reference

Why use Service if it runs in the same thread in android

I was going through Bound Service in Android Developer website. I thought I understood the service enough but I just found another way of connecting service through Using a Messenger class especially for local service. There I got confused. Maybe I got the concept wrong.
Here is my understanding of Android Service. You create a service when
You want to do separate jobs in the background.
You want to make it a separate process.
You want to make it run in a lifecycle that's independent of the component that started it.
Confusion is the first item in the list, the definition of the background. Isn't the background a thread or process? I never thought that it can run on the main thread.
Here is the caution of service in the dev pages about.
Caution: A service runs in the main thread of its hosting process—the service does not create its own thread and does not run in a separate process (unless you specify otherwise). This means that, if your service is going to do any CPU intensive work or blocking operations (such as MP3 playback or networking), you should create a new thread within the service to do that work. By using a separate thread, you will reduce the risk of Application Not Responding (ANR) errors and the application's main thread can remain dedicated to user interaction with your activities.
Questions
Why does one choose to use service if the service function will anyway run on the main thread?
Do we have to write a service only to block ANR even if the time-consuming job is done in the main thread? Assume the service is only for my application.
Are there any practical cases or reasons to use a service as private and running in the same thread?

Application main thread is not always the UI thread. For example, when Activity is stopped, the onStop() is invoked, hence the UI thread is taken away from that Activity and moved to another Activity within the same or a different application. However it doesn't mean the application is no longer active, it can continue working in the background until it is closed either by OS or by user. Then who keeps it running in the background? It is the main thread and not the UI thread.
What are services
In Android, a Service is an application component that can perform
long-running operations in the background on the UI thread. By
background, it means that it doesn’t have a user interface. A Service
runs on the main thread of the calling Component’s process by default
(and hence can degrade responsiveness and cause ANRs), hence you
should create a new Thread to perform long running operations. A
Service can also be made to run in a completely different process.
Unlike Activity components, Services do not have any graphical
interfaces. Also Broadcast Receivers are for receiving broadcast
messages (broadcast, multicast, unicast) and perform short tasks
whereas Services are meant to do lengthy processing like streaming
music, network transactions, file I/O, interact with databases, etc.
When a Service is started by an application component like an Activity
it runs in the background and keeps running even if the user switches
to another application or the starting component is itself destroyed
Why use service
Services are given higher priority than other Background processes and
hence it’s less likely that Android will terminate it. Although it can
be configured to restart once there is ample resources available
again. You should go through the different processes and their
priority/important level in the documentation on processes and
threads. Assigning them the same priority as foreground activities is
definitely possible in which case it’ll need to have a visible
notification active (generally used for Services playing music).
Use IntentService if you don't want to fiddle with managing threads on your own. Otherwise, use AsyncTasks.
Please read this excellent article to understand more in detail and also read this answer.

Service basically runs in UI thread or main thread.But,if we are going to perform long running operations in service,we need to create a background thread and perform that task.
But why we have to use service?
Now let's think of Music Application.We need songs to be played continuously even if we leave music app.If we use activities,we can't achieve above requirement.So,service helps in these kind of scenarios.Even if the app is not in foreground, service keeps on running and we are able to listen to songs.This is why we use service even though it runs on main thread.

In short, Services runs on the background of the UI thread.
You can perform tasks like client-server authentication or write to a database where the tasks are done in the background with no graphical interface.
But if you're doing a really long processing tasks that could freeze the interface, you use a service on a separate thread.
eg of a Service on a separate thread is IntentService

Where to create own thread, Inside service class or Inside the activity form where we give call to the service

In android A service runs in the main thread of its hosting process, I want to know that if I want to create my own thread, then where to create it, Inside service class or Inside the activity form where we give call to the service ..?
thanks in advance

Generally, if you need your thread to persist after your activity is gone, then you need to run it in a service. The point of a service is to persist beyond the life of an activity.
Passing data across activities, services and threads may complicate the answer, and so you may end up running a thread in a service even if the thread does not persist after the activity, but that is a rare case.

Your activity should start your service, then start your thread inside the service. If you put your service launching code in a thread, all that would do is start the thread in the background but the service (and consequently the code you want to run in the background) would still run on the Main thread
If your aren't trying do some continuously running task, I would suggest using an IntentService. With an IntentService all most of the thread handling and the service cleanup is done for you.

Service vs Thread in Android

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.

Android NonUI Thread making application "not respond"

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

Thread started by an application in android

If I raise a thread in via an Application in Android, how long does the thread life and is active?
Does a thread continue to live when the user leaves the application. If so for how long?

Until the Thread completes. You should look into AsyncTask class instead of regular Threads though.

Yeah in Android threads are like the old-fashion Java thread. They do not have a predefined lifecylvce like Services, Activities etc. If you start a new thread you must also be responsible of its lifecycle (i.e. terminate it when you do not need it anymore and keep it alive untill you need it).
EDIT: see here and this other question. As I was saying, the thread remains alive untill it has work to do. Regard that if the process of your application is destroied by the O.S. then also the thread you have created will be destroyed as well.