Android Game Development - Level progression methods

I am currently developing an Android game that is similar to a classic arcade space shooter. Thus far I have almost everything finished, but my code is not quite to my liking and I am trying to find out how to improve it.

The problem I am having is with enemies and other objects entering the screen.

Currently I am using a Runnable object that I pass to a thread, and in this Runnable is an array of all of the distances that will trigger new enemies to come in from the top or sides of the screen. In the run() method, I check the time and if the System.uptimeMillis() is greater than or equal to an element in my array, I fire another method that uses a switch statement to determine the event to run.

This is all becoming quite a hassle to manage and that is why I was wondering if anybody know of a more efficient and neater way to manager the queued enemies.

Also, my array I create is of 200-some objects and once they are off the screen I was nulling them. Obviously this was firing of the GC too often开发者_Python百科 for a well-performing game. Is it best just to reuse enemies that are destroyed or go off screen? Or is there a better way for this as well? (I am just ensuring that my program is the best it can be before it ventures into the wilds of the Market)

Thank you in advance,

-Roflha

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I suggest you look at this code for reference. It has a good way of dealing with objects, collisions and stuff.

And its written by a google employee which always sounds cool for some reason.