I've made a game using libgdx. On m'y HTC One X, the game works good, even if there are some lags but only at the beginning. I wanted to try it on an older phone (well a less powerfull phone), a Samsung Galaxy Y, and on it my game is always very slow. How could I know how to fix it?
How could I fix it?
Well, first off, I would look "what" is actually making the game lag. For example, are you using sprites that are like 2048 pixels in y and x pixel then you should look forward to break it down.
Also, maybe it's an certain miss conception of code. Maybe there are some unnecessary function calls in your game loop?
You'd be better with using an profiler, in order to see where your programm starts to fall off in FPS.
I don't know the Samsung Galaxy Y, it's possible that it has not enough power to run a game.