Xcode’s iOS-app simulator helpfully provides four sets of GPS data for development of apps using CLLocationManager: Apple campus, city bike ride, city run, and highway drive. Josh Adams developed an app that uses GPS and found this data deficient in two ways. First, the data contain no altitudes other than “0”. Altitude tracking is important for his app, and this inability to test his app’s altitude tracking was unacceptable. Second, the simulator provides data only at 1X speed. During his develop/run/debug/run cycle, he became impatient waiting for the simulator to provide GPS data to his app, even using the relatively fast-moving highway-drive mode.
In an epic bout of yak shaving, Adams remedied these deficiencies by developing GpxLocationManager. This class can replace CLLocationManager at compile- or runtime, allowing clients to access GPS data from two sources: GPX files and arrays of CLLocations. In particular, GpxLocationManager invokes its clients’ didUpdateLocation() method with GPS data from either of these two sources. GpxLocationManager can provide this data at the same speed it was recorded or sped up by an arbitrary amount. Thanks to the hard work of Nehal Kanetkar, GpxLocationManager supports simulating course and speed.
The maintainers welcome pull requests for GpxLocationManager.
Adams demonstrated GpxLocationManager to the Swift Language User Group in San Francisco. Realm was kind enough to record, transcribe, and host his talk.
To get the project up and running, please install SwiftLint by running brew install swiftlint.
Here are the steps to use GpxLocationManager in your app.
1. Obtain the framework via CocoaPods or by copying the files GpxLocationManager.swift, LocationManager.swift, and GpxParser.swift to your project. If you go the CocoaPods route, you will need to import GpxLocationManager in any file using classes from that framework.
2. If you want GpxLocationManager to use data from the GPX file gpxFile.gpx, initialize as follows:
let locationManager = LocationManager(type: .gpxFile("gpxFile"))If you want GpxLocationManager to use an array of CLLocations called locations, initialize as follows:
let locationManager = LocationManager(type: .locations(locations))If you want data to come from a real CLLocationManager, initialize as follows:
let locationManager = LocationManager(type: .coreLocation)3. Set the LocationManager’s delegate to something that implements CLLocationManagerDelegate.
4. Optionally set the LocationManager’s secondLength property to something other than 1.0. A lower value speeds up the underlying GpxLocationManager. If the LocationManager wraps a CLLocationManager, this property has no effect.
5. Invoke the LocationManager’s startUpdatingLocation() method. The LocationManager will start calling the delegate’s didUpdateLocations() method using data from the device’s GPS, the simulator’s GPS, the GPX file you specified, or the CLLocation array you specified.
6. Invoke the LocationManager’s stopUpdatingLocation() method to pause the location updates.
7. If you are running a GpxLocationManager and want to stop the NSTimer causing it to invoke didUpdateLocations(), invoke the LocationManager’s kill() method. This method has no effect if there is an underlying CLLocationManager.
Because LocationManager can wrap either a GpxLocationManager or CLLocationManager, swapping those two at runtime is easy. If you will never need the data from a CLLocationManager, just use GpxLocationManager.
Run the Demo scheme. DemoViewController.swift shows the three ways to instantiate LocationManager.
Click here to watch an older version of the demo in action. In this run, GpxLocationManager gets GPS data from a GPX file, and the demo plays the data back sped up ten times. Note that a 40-minute run takes four minutes to watch.
If you use or are intrigued by GpxLocationManager, please consider starring the repo.
GpxLocationManager is not a functionally complete replacement for CLLocationManager. The former lacks much of the latter’s functionality. GpxLocationManager’s primary function is to invoke didUpdateLocations() with arbitrary location data. That said, GpxLocationManager could certainly serve as a starting point for a functionally complete replacement for CLLocationManager.
GpxLocationManager correctly parses GPX files created by iSmoothRun, Runmeter, and Runkeeper. Adams has not tested GPX files from other sources.
Some apps currently using GpxLocationManager include RaceRunner and Touchdown.
Josh Adams (Twitter | GitHub | Website) created GpxLocationManager. He and Nehal Kanetkar (Twitter | GitHub | Website) maintain it.
The MIT License (MIT)
Copyright (c) 2015 Josh Adams
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