Does the apple warranty cover a cracked screen for an ipod itouch 4G? How

NOPE - NOT covered under an Apple warranty.
Called "physical damage because YOU dropped it.
Water damage - NOPE - not covered - you left it in the rain.
Run over by a truck - NOPE - physical damage.

Warranty is for a battery that went bad or caught fire. I software glitch that locked it up.

A warranty is for something that goes wrong due to the manufacturer being at fault that was out of your control and you did not cause.