how can i animate image that moves up automatically

hi i am new to iphone. what i need is i want to display an image for example balloon. when ever i click the button the balloon automatically start moveing up vertically from bottom of the simulator to top of the simulator.While it reaches top of the simulator automatically it moves towards开发者_运维知识库 down.How can i done this.please post any relevant code or link.Thank you in Advance.

Have a look at this example from Apple you just need to recognize the first touch on the balloon and then make it move wherever you want (by using an animation or manually redrawing the UIImageView representing the balloon each time using a NSTimer)