A stepper is a two-segment control used to increase or decrease an incremental value. By default, one segment of a stepper displays a plus symbol and the other displays a minus symbol. These symbols can be replaced with custom images, if desired.
Make the value affected by the stepper obvious. A stepper itself doesn’t display any values, so make sure people know which value they’re changing when they use a stepper.
Don’t use a stepper when large value changes are likely. Steppers work well for making small changes that require a few taps. On a printing screen, for example, it makes sense to use a stepper to set the number of copies because people rarely change this setting by much. On the other hand, it doesn’t make sense to use a stepper to choose a page range because even a reasonable page range would require lots of taps.
For developer guidance, see UIStepper.