A picker includes one or more scrollable lists of distinct values, each of which has a single selected value—appearing in darker text in the center of the view. A picker is often displayed at the bottom of the screen or in a popover when the user is editing a field or tapping a menu. Pickers can also appear inline, such as while editing a date in a Calendar event. The height of a picker is roughly the height of five rows of list values. The width of a picker is either the width of the screen or its enclosing view, depending on the device and context.
Use predictable and logically ordered values. Many values in a picker may be hidden when the scrollable lists are stationary. It's best when people can predict what these values are, such as with a list of alphabetized countries, so they can move through the lists quickly.
Avoid switching screens to show a picker. A picker works well when displayed in context, below or in close proximity to the field being edited.
Use a table instead of a picker for large value lists. Long lists can be tedious to navigate in a picker. A table has adjustable height and can include an index, making scrolling much faster.
For developer guidance, see UIPickerView.
A date picker is an efficient interface for selecting a specific date, time, or both. It also provides an interface for displaying a countdown timer.
A date picker has four modes, each of which presents a different set of selectable values.
- Date. Displays months, days of the month, and years.
- Time. Displays hours, minutes, and (optionally) an AM/PM designation.
- Date and time. Displays dates, hours, minutes, and (optionally) an AM/PM designation.
- Countdown timer. Displays hours and minutes, up to a maximum of 23 hours and 59 minutes.
The exact values shown in a date picker and their order depend upon the user’s locale.
Consider providing less granularity when specifying minutes. By default, a minute list includes 60 values (0 to 59). You can optionally increase the minute interval as long as it divides evenly into 60. For example, you might want quarter-hour intervals (0, 15, 30, and 45).
For developer guidance, see UIDatePicker.