This causes a findBugs warning. https://jenkins.catrob.at/job/Catroid-pullrequest-test/4213/findbugsResult/package.-411531754/HIGH/
You might be able to make this method static.
http://stackoverflow.com/questions/4869004/writing-to-a-static-variable-in-an-instance-method-why-is-this-a-bad-practice