QLPreviewController
A specialized view controller for previewing an item.
Declaration
class QLPreviewControllerOverview
A QLPreviewController can display previews for many common file types, including the following:
iWork documents
Microsoft Office documents
Rich text format, or RTF, documents
PDF files
Images
Text files with a uniform type identifier that conforms to the
public.texttype. To learn more, see Uniform Type Identifiers.Comma-separated values, or CSV, files
3D models in the USDZ format with both standalone and AR views for viewing the model
Providing data to a preview controller
To use a preview controller, you need to provide a data source object. The data source provides preview items to the controller and tells it how many items to include in a preview navigation list. If there’s more than one item in the list, a controller displays navigation arrows to let the user switch among the items. If you push a preview controller into view using a navigation controller, you can provide buttons in the navigation bar for moving through the navigation list.
For details on providing items to a preview controller, see QLPreviewControllerDataSource and QLPreviewItem.
Presenting a preview controller
You can present a QLPreviewController modally by calling present(_:animated:completion:) from a presenting UIViewController, or you can push it into view using a UINavigationController. The preview includes a title that the system derives from the last path component of the item URL. You can override it by implementing a previewItemTitle accessor for the preview item.
Previewing items in Mac apps built with Mac Catalyst
For Mac apps built with Mac Catalyst, presenting a QLPreviewController displays the preview in a QLPreviewPanel and dims the previously active window. However, unlike on iOS devices, where displaying a preview hides the presenting view controller, the previously visible window’s content remains visible in Mac apps built with Mac Catalyst. Be sure the content is appropriate to display while the QLPreviewPanel is visible.
In addition, the system doesn’t display a live preview if you embed the QLPreviewController in another view controller. Instead, it displays a thumbnail that matches the size of the preview controller’s view.