What exactly are contentOffset, ContentInset and ContentSize of a UIScrollView?

Photo by Nick de Partee on Unsplash

UIScrollView is one of the most versatile and useful controls in iOS, and has been around since iOS 2.0. It’s the basis for the very popular UITableView and it’s a great way to present content that’s larger to fit in a single screen view.

UIScrollView has a lot of instance properties, but contentInset, contentOffset, and contentSize are probably the most frequently used. One can do wonders with a complete understanding of these properties—starting with a stretchable toolbar to pinch in pinch out of images and a lot of other cool stuff.

contentOffset

contentOffset is the point at which the origin of the content view is offset from the origin of the scroll view. In other words, it is where the user has currently scrolled within the scroll view. This obviously changes as the user scrolls.

contentOffset indicates the current position of the scroll view content, relative to the origin coordinates on the top-left corner. The content size remains the same, but the content offset changes to respond to user interaction.

contentInset

The contentInset is how much the content is visually inset inside the scroll view. It is the custom distance that the content view is inset from the safe area or scroll view edges.

contentInset allows you to specify margins or padding around the content in the scrollview. You can specify the margin programmatically as follows:

contentSize

contentSize defines how big the scrollable content is. It is the size of the content within the UIScrollView and how long it can be within the UIScrollView.

The scroll view must know the size of the content-view so it knows when to stop scrolling. its default value is zero, and it must be set to use any scroll view, even if the content-size is smaller than the scroll view’s own size.

Putting it all together

This is how properties are placed over scrollView

Some of the popular UIComponents in iOS i.e. UITextView, UITableView & UICollectionView are inherited from the UIScrollView class, so all of these properties are applicable to UITextView, UITableView & UICollectionView as well.

Thanks for reading!