Scroll Views
A scroll view allows users to browse content, such as text in a document or a collection of images, that’s larger than the visible area. As people swipe, flick, drag, tap, and pinch, a scroll view follows the gesture, revealing or zooming content in a way that feels natural. A scroll view itself has no appearance, but does display transient scrolling indicators as people interact with it. A scroll view can also be configured to operate in paging mode, where scrolling reveals an entirely new page of content rather than moving around the current page.
Support zoom behavior appropriately. If it makes sense in your app, let people pinch or double-tap to zoom in and out. When you enable zoom, set maximum and minimum scale values that make sense. For example, zooming in on text until a single character fills the screen probably doesn’t make sense in most apps.
Consider showing a page control element when a scroll view is in paging mode. A page control shows how many pages, screens, or other chunks of content are available and indicates which one is currently visible. If you show a page control with a scroll view, disable the scrolling indicator on the same axis to avoid confusion. For additional guidance, see Page Controls.
Don’t place a scroll view inside of another scroll view. Doing so creates an unpredictable interface that’s difficult to control.
In general, display one scroll view at a time. People often make large swipe gestures when scrolling, and it can be hard to avoid interacting with a neighboring scroll view on the same screen. If you need to put two scroll views on one screen, consider allowing them to scroll in different directions so one gesture is less likely to affect both views. For example, when an iPhone is in portrait orientation, the Stocks app shows stock quotes that scroll vertically above company-specific information that scrolls horizontally.
For implementation details, see UIScrollView.