I'm trying to draw a bouncing ball on a canvas created using dart and html bu I keep getting the error Uncaught Error: Invalid argument: null. What do I need to change?
I'm pretty new to dart and I'm using this example to learn
The code is here https://dartpad.dartlang.org/23dc04cc02644fce59f1417ec378ebf9
I want to make the ball bounce when the Mouse (Touchpad) is moved on the canvas but the ball is still