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In my game, there is an game object class that need to use Handler to post a delay Runnable. However, everything I try to create an Handler in the object class, I receive error message:

Can't create handler inside thread that has not called Looper.prepare()

I've Googled some solution, but all of them use another solution, not Handler. Is there any solution to use Handler in a normal class? Or any solution to run a Runnable after a determined delay?

I can't use sleep, because it paused all my game!

Thank you.

Luke Vo
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  • You might want to check out http://stackoverflow.com/questions/5193913/handlers-messagequeue-looper-do-they-all-run-on-the-ui-thread as well. The answer discusses Handlers, the looper etc. a bit in-depth. It sure gave me some insights, maybe it can help you too. :) – rogerkk Mar 10 '11 at 12:02

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You are probably creating the Handler from a non-UI thread. Either (1) you attach your handler explicitly to the UI thread by passing the UI thread's looper to Handlers constructor, which means that messages posted to the Handler are also executed on the UI thread, or (2) you create a new Looper for the non-UI-thread: see here.

edit regarding (1): you would have to somehow pass the UI thread's looper to the "game object", for example when it is created. You can get a reference to UI's looper by calling getMainLooper() on a context (e.g. from an activity).

An alternative would be to create the handler in the activity and just pass the handler to your game object.

user634618
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  • @user634618 Thank you for your advice! Creating a Handler in Activity and pass it to the object is the best and simplest solution! – Luke Vo Mar 11 '11 at 05:10