Tutorial: How to use QLPreviewController to preview files.

This tutorial will talk about implementation of preview feature of documents, images and files available on iOS 4.0 onwards. Apple reference document says:

A Quick Look preview controller can display previews for the following items:

• iWork documents
• Microsoft Office documents (Office ‘97 and newer)
• Rich Text Format (RTF) documents
• PDF files
• Images
• Text files whose uniform type identifier (UTI) conforms to the public.text type (see Uniform Type Identifiers Reference)
• Comma-separated value (csv) files

You need to add QuickLook.framework in your project. and import QuickLook/QuickLook.h
and add protocols <QLPreviewControllerDataSource,QLPreviewControllerDelegate>

QLPreviewController *previewController=[[QLPreviewController alloc]init];

previewController.delegate=self;

previewController.dataSource=self;

[self presentModalViewController:previewController animated:YES];

[previewController.navigationItem setRightBarButtonItem:nil];

You need to add datasource methods for sure. Return more than 1 for numberOfPreviewItemsInPreviewController if you want user to be able to preview next and previous file while in preview mode. Else return 1 if you want user to exclusively preview only selected file.

- (NSInteger)numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller

- (id <QLPreviewItem>)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index

You may add delegate methods  optionally depending on your requirements. In Sample code, I have used these delegate methods to add the zooming effect where the preview seems to come out of the same button clicked by user.

- (BOOL)previewController:(QLPreviewController *)controller shouldOpenURL:(NSURL *)url forPreviewItem:(id <QLPreviewItem>)item

- (CGRect)previewController:(QLPreviewController *)controller frameForPreviewItem:(id <QLPreviewItem>)item inSourceView:(UIView **)view

For more information, you can view the Apple reference document.

Link of the sample code to download.