Testing iOS 4.0 Location APIs on the iPhone

on August 15, 2010, 1:39 am

In the course of investigating the new iOS 4.0 location APIs, I have found that the documentation was not entirely clear when describing the various cases associated with suspended and terminated apps on the device. Combining this lack of clarity with the inability to set location through the iPhone simulator, resulted in a reasonable amount of frustration.

I found the only way to effectively test this stuff is to get on a train and travel around with your app in the debugger.

This is not exactly ideal, so I built a simple test harness to switch between the various location APIs and log all the responses that the app receives. You are welcome to download, use, modify, etc at your own risk. It is pretty straightforward, but might save you some time building something to test this stuff out. If there are any glaring errors, please let me know.

Update 17 August 2010

I have found testing the app that when I am woken up from a terminated state, I get very little time to do anything. My first cut logging code was fairly inefficient so I have updated the app to do the bare minimum to write out log messages.

I also found a bug in my wake up code that instantiated a CLLocation and assigned it to a CLLocationManager, this compiles without no warnings because init returns an id which you can happily assign to anything you like, but fails when the app tries to set a delegate on the object. I have fixed this in the current version so you should get all your wake up log messages.

Update 18 August 2010

With some more testing of the wake from terminate case, I discovered that I was adding the view controller to the window in the wrong place. Adding it in didFinishLaunchingWithOptions is fine if you aren't using background location services, because there isn't a case where you don't want to create the UI. In the background location processing case, you want to be able to start up and not do all the UI overhead. So I have moved that code into applicationDidBecomeActive. That way when the app gets started by the user it adds the subview if the UI has been initialized (by checking if the window has any subviews).

Update 20 August 2010

Thanks to Daniel's suggestion I have added a Github repo for the project.

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