CODEWITHSUNDEEP
android
PaulG
PaulG

Reputation: 7102

Java exceptions when trying to modify ArrayList

I'm working on an Android game which fires an onDraw() method 30 times per second.

In this method I am iterating through an ArrayList of objects and drawing them with an object.Draw() method I created.

My problem is, I want to add objects to this ArrayList in the game's onTouchEvent(), but I sometimes get the following error:

java.util.ConcurrentModificationException

I know what's happening here, the onTouchEvent() fires when I touch the screen, so objects are being added to my ArrayList, but sometimes this happens as my onDraw() method is firing, which iterates through my ArrayList, and this causes the exception. Makes sense.

My question is, how can I add objects to my ArrayList when I touch the screen if it's being iterated through in my onDraw() method? Can I try to detect touch events in my onDraw() method? This way there will never be a problem. This is my first time programming games for Android, how is this kind of thing usually handled?

Upvotes: 0

Views: 57

Answers (1)

Konstantin Burov
Konstantin Burov

Reputation: 69228

It looks like you're accessing and modifying the list from different threads. Try synchronizing access to the list (so only one thread will have access to it at a time).

Another option might be to use CopyOnWriteArrayList.

Upvotes: 1

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