iphone: location manager + adwhirl = battery drain :(

Question

In my app I am using CLLocationManager and AdWhirl. I have made no specific development regarding background mode: I don't want my app to be working when it is in background, i.e. when the user press the "home button", GPS location should no be updated.

Yesterday evening I pressed "home button", and this morning the iPhone was out of battery. It's an iPhone 4 with iOS 4.1, not jailbreaked, and there is no background app running.

The battery was about 35% yesterday evening, and 0% this morning (iPhone was shutdown).

I have set breakpoint in my delegate, which is called each time GPS location is updated. When app is in background mode, delegate is not called. So I'm thinking GPS is really disabled in background mode: ok.

This morning, I am following battery drain: it's about 1% drop each 15 min. I think it a bit too much.

Should I do something specific when the app goes to background mode? Do you think this 1% drop is normal?

Answer 1

Yes, internet access and GPS are two big drains on battery. I don't know at all what you mean with normal, since no other apps are running you've concluded that that is in fact what happens :) Assuming you've tested with NO apps running and didn't get 1% per 15 minutes...

For adwhirl, it's unknown whether it already stops accessing the internet when the app goes into the background, but you can add this to your App Delegate:

- (void)applicationDidEnterBackground:(UIApplication *)application {
    /*
     Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
     If your application supports background execution, called instead of applicationWillTerminate: when the user quits.
     */
    [lm stopUpdatingLocation];
    [adView ignoreAutoRefreshTimer]
}


- (void)applicationWillEnterForeground:(UIApplication *)application {
    /*
     Called as part of  transition from the background to the active state: here you can undo many of the changes made on entering the background.
     */
    [adView doNotIgnoreAutoRefreshTimer]
    [lm startUpdatingLocation];
}

(lm and adView are the Location Manager object and the adWhirlView, both declared in the App Delegate. I've found it more useful to do all location managing via methods I make in the App Delegate.)