Java: Reading GPX data from Endomondo

I’ve started using Endomondo as my primary workout application for a couple of weeks now and although it is a great app I want to have more control over my data. Luckily for us endomondo users they offer a export function that exports the workouts in GPX format.

Today I’ve been playing around with this library: https://sourceforge.net/projects/gpxparser/ and get the GPX file from Endomondo to be parsed succesfully..

So first of all I created a new project in my Eclipse and imported the GPX parser from the website into another project. I downloaded a file from my endomondo account and wrote a little code:

As you can see. Nothing to fancy. So now what? If we take a sneak peek at the file http://www.jeroensomhorst.eu/wp-content/uploads/20140816_100357.gpx you will see there is no information whatsoever about distance, speed, average heartrate and so on. We have to add that ourselves. Luckily its GNU license so I can edit the source as I please (or atleast that’s what I make out of the license..).

Let start by refactor the GPXParser class. I want to generate a custom GPX class that implements my interface EndomondoGPX. First create the interface

Nice, isn’t? Next create a new class called EndomondoGPX

The code is pretty simple. There are some util functions there for retrieving all the trackpoints. This method also sorts them by time.

To make this happen I had to make  change to class that is base for all classes in the default GPX parser. The extension class. I had to make it abstract, implement a interface (comparable !) and make a abstract method public int compareTo(Object o1, Object o2).

All other classes such as waypoint should implement the compareTo. For this patch I only need to add the compareTo to the Waypoint class.

After some testing I found out there is a little bug in the GPX parser. When there is more then 1 trkseg node it will overide that node all the time. So you will end up with only the last trkseg node. In this case (see file) it will only contain one trkseg with one trkpt node. Not what we want!

The fix for this is the following method in Track.java

It won’t overwrite all trackpoints for the current track it will add them. For now that is correct but I wont recommend it for all GPX files out there.

So, when that is done. We can start changing our Parser class.

Open up the GPXParser class and add the following method:

and refactor the method signature of parseGPX to

Now add the following method for backwards compatability:

What we have done is pretty simple. First we created a new method to parse given GPX file (using inputstream) to a object of our own. We tell the GPXParser to parse the xml to our own instance of the GPX class. (in our case EndomondoGPX ).

Next, because we added that method we had to change the default method. We made it private, so that nobody can use it behind our back and we added a new parameter an instance of the GPX class. Inside this method we had to remove the  the GPX gpx = new GPX() because we now send it in as a parameter;

Last of but least we had to add a new method for backwards compatability. All this does is creating a new default GPX object and pass it into the changed method. We can now change our first code snippet to :

As you can see we have now full control what type of GPX object we get.

To get this all working by the way you also need to create a new HeartRateExtensionParser class. This class is used to parse extensions that comes with Endomondo.

If you want to code.. let me know. It is still little buggy (the distance calculations seems to be a bit odd compared to endomondo ) but it works.

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