Android drawing app
https://code.tutsplus.com/tutorials/android-sdk-create-a-drawing-app-touch-interaction--mobile-19202
Progressbar / Task-Thread-Example https://www.mkyong.com/android/android-progress-bar-example/
https://www.tutlane.com/tutorial/android/android-progressbar-with-examples
(draw short strokes in one paint) stop painting < 1/2 second => can continue painting
stop painting > 1 second => post stroke max points painted => post stroke