Stop Service in Activity onDestroy

Can I safely stop a Service in my main Activity's onDestroy method? I know that onDestroy is not guaranteed to be called, but I also do want to keep my Service running until the app is destroyed.

I'm thinking that maybe in all situations where the activity is destroyed, the service would also be destroyed?

回答1:

Yes it is safe to do it in onDestroy. Because before killing your activity background service or forground service that is bound to component will get killed by system as priority for service running in background is lesser then component you are interacting with.

回答2:

You can stop a service in the onDestroy of an activity, but to do it successfully requires either:

Running a Service in the Foreground

A foreground service is a service that's considered to be something the user is actively aware of and thus not a candidate for the system to kill when low on memory. A foreground service must provide a notification for the status bar, which is placed under the "Ongoing" heading, which means that the notification cannot be dismissed unless the service is either stopped or removed from the foreground.

For example, a music player that plays music from a service should be set to run in the foreground, because the user is explicitly aware of its operation. The notification in the status bar might indicate the current song and allow the user to launch an activity to interact with the music player.

or Managing Bound Services

A bound service is the server in a client-server interface. A bound service allows components (such as activities) to bind to the service, send requests, receive responses, and even perform interprocess communication (IPC). A bound service typically lives only while it serves another application component and does not run in the background indefinitely

In all your activities, manage any resources you have created within that activity and with a null check, close them down. Like you have in your service class. If you want to override the parent onDestroy, place your custom code before super.onDestroy.

There's more detail about this here.

but I also do want to keep my Service running until the app is destroyed.

The activity can remain on the stack in the stopped state and will not be destroyed until more memory is needed. This means that there is no fixed time that the service will continue to run until the activity is destroyed.

Activity Lifecycle

If an activity is completely obscured by another activity, it is stopped. It still retains all state and member information, however, it is no longer visible to the user so its window is hidden and it will often be killed by the system when memory is needed elsewhere.

The entire lifetime of an activity happens between the first call to onCreate(Bundle) through to a single final call to onDestroy(). An activity will do all setup of "global" state in onCreate(), and release all remaining resources in onDestroy(). For example, if it has a thread running in the background to download data from the network, it may create that thread in onCreate() and then stop the thread in onDestroy().

To ensure that all your resources are cleaned up, you could either call finish() on the activity, or end the service in the onStop() method or use a timer in the onStop(), that will end the service or destroy the activity after x time.

The problem with calling finish() is that if the use navigates back to the activity quickly, it needs to be recreated. The problem with using stop() is if the activity is restarted the service will need to be restarted. So a timer could be a way to keep the activities natural state preserved to allow user navigation, but it would need to be stopped if the activity resumes in onResume().

For protected void onDestroy ()

Perform any final cleanup before an activity is destroyed. This can happen either because the activity is finishing (someone called finish() on it, or because the system is temporarily destroying this instance of the activity to save space. You can distinguish between these two scenarios with the isFinishing() method.