Android Joystick for 2D Movement

I'm trying to put together a 2D shooting game for the android and I'm completely stuck here on what to do (I've searched for hours already and I don't think I'm heading towards the right direction). I want to have a joy stick on the button left of my android device that controls the player's movement to either go up, down, left, or right. Any clue where or how I can possibly go about this?