how to completely get rid of an activity's GUI (avoid a black screen)

Question

I\'m trying to write a very simple app that will do just one very simple non-GUI action, then display a short message (using toast, on top of what was already on the screen, e.g

Answer 1

Sounds like a job for an IntentService. You send it an intent, and if it isn't running it starts, then it treats all received intents, then it stops. Short and simple.