Develop Reference

How to have a service to run eternally on Android?

Search engines and Android developer website didn't help and I guess you can help with my problem.
I want to make an app for personal use, which is supposed to run all the time on my old tablet (powered all the time). The app will have several features requiring user interaction but independent of those, it should run a background job to check something continuously (real time!) for instance sound detection. It should also always try to connect another device on the network.
That means that job needs to run almost eternally without being killed. Some comments I have found suggested AlarmManager or BroadcastReceiver. But those are triggered by very defined triggers (either time or broadcast). I don't want that, because it should perform its task continuously all the time. This background job should also be able to communicate with the main Activity of my app to report what it is doing and allow user to interact with it (change settings of the job for instance).
Do you know any way how to accomplish this? Is IntentService correct choice for this (hoping that it won't get killed or maybe I should let the Activity to restart it?)
Thanks!

Do you know any way how to accomplish this?
Build your own custom ROM, with a modified version of Android that contains your code as a native Linux daemon.
Otherwise, what you want is technically impossible.
You can come fairly close by using a foreground Service (not an IntentService) and returning START_STICKY or START_REDELIVER_INTENT from onStartCommand(). Android may terminate your process from time to time, but it should restart your service automatically after a short while. That service can use its own background threads to do whatever it is that you are trying to do.

Phonegap app on Android platform - keep app running

I have a Phonegap app that functions as a communication service for a specific group of people. Using the local notification plugin found on the phonegap-plugins GitHub page, I have implemented notifications into the app, so that whenever someone receives a new message, a notification will appear if the app is in the background.
After about an hour, though, no more notifications will occur, and it appears the process was killed. When I go back into the app, it starts completely over instead of resuming from where I last left off. I'm assuming that after a certain amount of time, Android stopped running the app in the background.
Does anyone know how to keep the app running in the background until it is told by the user to stop, and prevent Android from killing the process?

As CommonsWare suggests, you could write a dummy service to keep your app alive, but also as he rightly suggests, if you're going to go to the effort of writing a native dummy service, you may as well write the actual service natively and have done with it.
As a bit of a quick and dirty solution, you could maybe use a partial wakelock (see here) to keep the CPU running your app while it's in the background.
I successfully used this approach to keep my Phonegap-based walk navigation apps alive in the background so they can continue to receive and process position updates.
In your case, staying alive to receive notifications isn't exactly what a partial wakelock was intended for and so I'm unsure whether android will kill your app anyway after a while since it's not doing anything (unlike mine which is constantly receiving and processing position updates) but it might do the job without needing to write a service, so may be worth a try.
Have a look at my answer to this question which contains my code for an updated version of the PowerManagement plugin for Android. I updated the plugin for use with Cordova 2.8.0 but also extended it to be able to acquire a partial wakelock.

Good Practices for running Android App in the Background

I have a VOIP app that I would like to always run in the background to make it responsive to incoming calls. Reading through some forums I found running the app in the background would cause a battery drain.
Are there good practices that I should follow so as to run the app in the background?

Reading through some forums I found running the app in the background would cause a battery drain.
It is more that having something run all the time increases your opportunity to drain the battery.
Are there good practices that I should follow so as to run the app in the background?
Being a VOIP app already violates some of the "good practices". For example, you will need to (try to) have a service that runs forever, to maintain your open socket connection to the VOIP server. And, depending upon how your networking is set up, you might need to try maintaining a WifiLock, which will drain the battery.
Generally speaking, then, you just want to make sure that your service is doing as little as possible except when a call is in progress. For example, while you may need to send packets over to the VOIP server periodically to keep your connection alive, try to do that as infrequently as you can.

There are many smart VoIP applications that use Push Notification feature. That will not eat up as much battery, but you must have a consistent internet connection. One such option is Axvoice. Check out their apps at: http://www.axvoice.com/support/mobile-voip-applications.html
They will also run in the background like other apps, but the difference between Axvoice and other apps is you can reduce battery consumption because it will not be communicating with live servers all the time. Please have a look at this: http://www.wikihow.com/Save-Battery-Power-on-an-Android

Use a Broadcast Reciever. It is documented here
http://developer.android.com/reference/android/content/BroadcastReceiver.html
A BroadcastReciever will execute it's code when the specified broadcast is broadcasted through the system. In other words when you receive a call the system sends out a broadcast saying that there is an incoming call. If your receiver is made to pick up on that broadcast than it will react. Think of it like the Android system is broadcasting a lot of different radio stations and a BroadcastReciever is like a radio. You can set it to pick up whatever broadcast you want and execute some code when it does.

How to poll for current time in a Service?

I did a search before asking so please don't tell me to do that.
I'm relatively new to Android so I get confused easily.
I'm making a simple app that changes the ringer volume according to time. For this purpose, I know I need a service that keeps running in the bg and monitor time. However, I really don't know how to approach this. I have the Professional Android Application Development book but haven't found anything that helps in there.
My question:
How to constantly check time without destroying the battery
If my code is needed (as proof of me actually working on this), I'll post.

You don't need a service. Use the AlarmManager class. Its like an alarm clock and it exactly what you need for this type of app.

need a service that keeps running in the bg and monitor time
No. Actually that's not how to do it. Services on android are different than your normal windows service/unix daemon. They should do their job and then stop themself until they get started again - to save battery.
You should start your service at a certain point in time by using the AlarmManager, it sends the launch intent to run the service. When the service is finished doing what it's supposed to do (change the rintone volume here), use Service.stopSelf() to kill it.

Can I keep Android App alive in background?

I currently have programmed a normal Andorid-App (no Service). It contains a timer for periodic checks. To avoid hassle with a service and communication between Service and App I ask myself whether there is a way to keep an App that is no longer in foreground alive.
Currently when I "close" the App, it is still alive until Android OS decides to kill it. Is there a way to avoid this kill - e.g. by a certain command in "onDestroy" or a certain App-flag?
My App is quite complex and I do not want to implement a Service as this -especially the communication/binding- increases the complexity. Is there an "easy way" or am I really forced to use Service+App? Maybe there is a trick to register the App for sth. special that has the side-effect that Android OS does not kill it when it is in the background.
Edit for better understanding: It is ok that the GUI can go into the background (vanish) when the user wants it, so my question is not how to let the GUI of my App permanently in the foreground. All I want is that the timer stays intact without the need for an additional Service.
Thank you all for ideas in advance!

Android is very unpredictable by the nature of the OS's killing selection and by the market fragmentation. I would not count 100% on anything being kept alive if it is crucial. However you can gamble and be pretty successful. This is what would help you:
Use very good "Best Practices" to keep your string pool and heap at a minimum as Android looks to kill memory hogs first off (and because you love what you do).
Add the persistent attribute to your application manifest tag.
To really help yourself out, run as a, or run a service because they are long running processes, are very light (if implemented well), and Android looks to kill these off lastly.
Give your service priority by running it as a foreground service.
Doing these things will increase the likely-hood that Android will not kill your application.

I don't think there is anything like that available. I suggest looking at AlarmManager for periodic tasks - this may mean you won't need to use a service.

The apps being available in the background is simply a caching measure by the android OS to avoid having to relaunch a frequenly used app from scratch. If you want to be able to count on your app running in the background, a Service is the correct solution. Its not the answer you are looking for, but I am not aware of any tricks to staying alive in the cache, and if there were any, I would not feel good about recommending them.