Is an android service guaranteed to call onDestroy()?

Question

The life cycle diagram of an Activity on an android does not guarantee that onDestroy() would be called, but that the process may be killed and the Activity is removed abruptly. The life cycle diagram of a Service on an android does guarantee that onDestroy() would be called. So I have two questions relating to this difference.

Firstly, if the Service is part of the same process as the Activity, is the Service onDestroy() called, though the Activity onDestroy() is not called? I would think not, as "killing a process" suggest that the operating system is stopping its threads and releasing its resources.

And if that is the case, can a Service-only-process be abruptly killed by the OS?

Answer 1

I'm not sure where you're seeing that a Service is guaranteed to have onDestroy() called. As far as I know, this isn't the case. If you read this page of the docs, it describes the conditions in which a service could be killed. So if you're asking if a process which hosts both an activity and service is being killed, will onDestroy() be called on the service (but not on the activity) then the answer is no; a service's onDestroy() will not necessarily be called. As to whether a service-only process can be abruptly killed by the OS: yes, it can. This is especially true when you have a lot of work to do, and your onStartCommand call only queues up the work to do asynchronously. Then the service will be spending the majority of its time not in the protected onCreate, onStartCommand or onDestroy methods.