About Scroll View Programming

At a Glance

The UIScrollView class provides the following functionality:

Scrolling content that will not fit entirely on the screen

Zooming content, allowing your application to support the standard pinch gestures to zoom in and out

Restricting scrolling to a single screen of content at a time (paging mode)

The UIScrollView class contains no specially defined view for the content that it displays; instead it simply scrolls its subviews. This simple model is possible because scroll views on iOS have no additional controls for initiating scrolling.

Basic View Scrolling Is the Easiest to Implement

Scrolling via drag or flick gestures requires no subclassing or delegation. With the exception of setting the content size of the UIScrollView instance programmatically, the entire interface can be created and designed in Interface Builder.

Related Chapters:: Creating and Configuring Scroll Views

To Support Pinch Zoom Gestures, You Use Delegation

Adding basic pinch-in and pinch-out zoom support requires that the scroll view use delegation. The delegate class must conform to the UIScrollViewDelegate protocol and implement a delegate method that specifies which of the scroll view’s subviews should be zoomed. You must also specify one, or both, of the minimum and maximum magnification factors.

If your application needs to support double-tap to zoom, two-finger touch to zoom out, and simple single touch scrolling and panning (in addition to the standard pinch gestures) you’ll need to implement code in your content view to handle this functionality.

Related Chapters:: Basic Zooming Using the Pinch Gestures .

To Support Pinch to Zoom and Tap to Zoom, You Implement Code in the Content View

If your application needs to support double-tap to zoom, two-finger touch to zoom out, and simple single-touch scrolling and panning (in addition to the standard pinch gestures), you implement code in your content view.

Related Chapters:: Zooming by Tapping .

To Support Paging Mode, You Need Only Three Subviews

To support paging mode, no subclassing or delegation is required. You simply specify the content size and enable paging mode. You can implement most paging applications using only three subviews, thereby saving memory space and increasing performance.

Related Notes:: Scrolling Using Paging Mode

Prerequisites

Before reading this guide, read App Programming Guide for iOS to understand the basic process for developing iOS applications. Also consider reading View Controller Programming Guide for iOS for general information about view controllers, which are frequently used in conjunction with scroll views.

How to Use This Document

The remaining chapters in this guide take you through increasingly complex tasks such as handling tap-to-zoom techniques, understanding the role of the delegate and its messaging sequence, and nesting scroll views in your application.

See Also

You will find the following sample-code projects to be instructive models for your own table view implementations:

Scrolling demonstrates basic scrolling.

PageControl: Using a Paginated UIScrollView demonstrates using scroll views in paging mode.

ScrollViewSuite of sample projects. These are advanced examples that demonstrate the tap-to-scroll techniques as well as other significantly advanced projects, including tiling to allow large, detailed images, to be displayed in a memory efficient manner.

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