Thanks for the confirmation.

 

I did try keyPressed() and keyTyped() etc.

 

I will rework the logic of the draw loop to allow for key strokes outside of the waiting period and then just process the keystrokes as necessary. 

1. void setup() {
2.   ...
3. }
4. 
   
5. void draw() {
6.   ...
7. }
8. 
   
9. void keyPressed() {
10.   println("key ["+key+"] (character code "+keyCode+") is being pressed!");
11. }
12. 
    
13. void keyReleased() {
14.   println("key ["+key+"] (character code "+keyCode+") was released!");
15. }

1. int x, y;
2. 
   
3. void setup() {
4.   size(300,300);
5.   x = width/2;
6.   y = height/2;
7.   ellipseMode(CENTER);
8.   noLoop(); 
9. }
10. 
    
11. void draw() {
12.   background(0,0,100);
13.   ellipse(x, y, 20, 20);
14. }
15. 
    
16. // keycodes for the cursor keys. mighty handy to have lying around.
17. // they have VK_ in front, because we don't want to overwrite LEFT and RIGHT
18. final int VK_UP=38, VK_LEFT=37, VK_DOWN=40, VK_RIGHT=39;
19. 
    
20. void keyPressed() {
21.   // up/down cursor handling
22.   if(keyCode==VK_UP) { y--; }
23.   else if(keyCode==VK_DOWN) { y++; }
24. 
    
25.   // left/right cursor handling
26.   else if(keyCode==VK_LEFT) { x--; }
27.   else if(keyCode==VK_RIGHT) { x++; }
28. 
    
29.   // draw a frame, and only one frame, with the updated information
30.   redraw();
31. }

(This does not do persistent key states, that's more work, so it will only let you press one key at a time. If you press both left and up, whichever key you pressed last "wins" the argument of who gets to update the x/y values)

- Pomax

Thanks Pomax, but as phi.lho confirmed, keypresses will not be processsed during a while loop.  I've tried the keyPressed function as well. It would not get called during a while loop. So essentially, any key press was ignored during a while loop.

 

I just had to rework the logic of the of my key handling so it would register outside of the waiting-for-serial-data-while-loop, and now that part is working ok.

The draw method is effectively your while loop. It gets called many times per second, so what you do instead is you make draw "do nothing" unless something has happened (like a key press or serial input) that warrants it to do something. Using an "if" is a good solution in terms of handling the event, but reading event states like keyPressed in draw() is a bad idea. Dealing with them in their own handlers, and then setting a flag that indicates that something should happen, named accordingly, is a much better approach. (like setting a boolean user_input_received to "true" if the input was the right input).