Where to stop a service during device rotation

Issue

When my activity starts, I start a service that fetches data then sends it back to the activity so it can update the UI.

If a config change occurs:

1. If I already have the fetched data, I save it in the onSaveInstanceState method.
2. If I haven't received the fetched data, I want to cancel the running service and relaunch it using the new activity.

So my onSaveInstanceState currently looks like this:

@Override
public void onSaveInstanceState (Bundle outState) {

    if (data != null) {
        outState.putSerializable(DATA_IN_BUNDLE, data);
    }

    // Stop any data fetching that may be going on.
    stopService(new Intent(this, FetchService.class));
}

However, I've noticed that this method is called during the normal starting of the activity, which I didn't know happened, so when it's run the service is always cancelled.

So my questions are:

1. Is this documented somewhere? Couldn't find anywhere that said onSaveInstanceState is called during activity start.
2. What would a better place to stop the service be? onConfigurationChanged?

Thanks!

Solution

You have a few choices:

1. Don't allow Android to kill and restart your Activity. Manage the config changes yourself. Usually this is pretty simple to do and prevents you from having to deal with stopping and restarting background stuff.

2. Pass the ServiceConnection (or whatever you are using as a communication channel to the Service) from the old Activity instance to the new Activity instance by using onRetainNonConfigurationInstance() and getLastNonConfigurationInstance()

3. Use a service-bus architecture, so that one Activity can start something and another Activity can register for the callback.

4. Send the response from the Service to the Activity using a broadcast Intent, which can be seen by the new Activity after a config change.

Answered By - David Wasser