Serial Event null pointer exception

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@l-arc-en-ciel

coordinates.remove(0);

You’re invoking method remove() inside serialEvent() callback, which is run by the Serial’s Thread btW!

That is a big no, no! You’re better off just using readString() inside serialEvent() to grab the received String.

However, parse that as JSONObject within draw() instead.

You can use the noLoop()/redraw() approach for a much easier event management:

redraw() / Reference

Map function worked in Processing 2 and early 3.. But broke in 3.5.3. Need guidance

Mutating the sketch’s main canvas outside the “Animation Thread” crashes the program! Callback serialEvent() is run by the Serial’s Thread btW. So even calling something like background() can be fatal! Actually, due to a bad design, any Processing function which depends on color() will get wrong results when they’re multithreading invoked! So any canvas mutating operations should be moved to draw() or called by it. Here’s a post link for…