Can't toast on a thread that has not called Looper.prepare()

[cristmasbox]

I'm working on an app which should download some files, but allways if i try it it gets this Error from the FetchListener:

java.lang.NullPointerException: Can't toast on a thread that has not called Looper.prepare()

I have checked, all inputs aren't null and I can't find a solution.
Can anyone help me?

[tonyofrancis]

@cristmasbox Fetch listener methods are called on a background thread for performance reasons. You would need to run any UI logic on the main thread.