Can I keep Android App alive in background?

Question

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!

Answer 1

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:

1. 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).
2. Add the persistent attribute to your application manifest tag.
3. 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.
4. 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.

Answer 2

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.

Answer 3

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.