Android : Example That Redraws On A Key Without Using A Thread?

Howdy android experts. I thought I knew something about programming.... lots of experience with microcontrollers and embedded simulations that run in a loop and read inputs, do some calcs, send outputs. After days of trying to write a program that prints out a count that increments with a key, I guess I know nothing of how the windows event driven model operates. I see examples that use another thread/task/program to accomplish what I thought would be a couple of lines. After the onCreate, lets say the screen says 'count 0'. The os is now running. right? Any click or key should get 'delivered' to the activity, so it seems I could have an onClick that says count++ and a setText or something and an invalidate, and Bob's Yer Uncle, but no it ain't that easy. I hereby declare that this task is impossible, and no one can show me how to do it.