That’s a long time ago that I played with these and 555 as well, I remember.
The best way to solve this is by using native android views. In the beginning, it seems complicated, but soon you will be used to it. I actually expected that you would be able to adapt the receiver code because very few changes were necessary. Just change the code in the plot(), draw(), and mouse() functions.
All the other code you can place in another tab, and don’t need to bother about it. I posted the code here because this topic is too big for others to search in.