{"id":37511,"date":"2018-07-25T14:21:06","date_gmt":"2018-07-25T21:21:06","guid":{"rendered":"https:\/\/blog.xamarin.com\/?p=37511"},"modified":"2019-09-23T08:15:11","modified_gmt":"2019-09-23T15:15:11","slug":"previewing-files-with-xamarin-ios","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/xamarin\/previewing-files-with-xamarin-ios\/","title":{"rendered":"Previewing Files Inside Your Xamarin.iOS App"},"content":{"rendered":"

\t\t\t\tIf your app interacts with files, such as email attachments or photos, allowing users to preview those files without leaving your app is a great way to enhance the user’s experience. Fortunately, iOS makes adding this feature simple by providing the document interaction controller and the Quick Look preview controller. In this post, you will learn the differences between the two options and how you can implement them in your app.<\/p>\n

All the code below is available as a sample app on GitHub<\/a>.<\/p>\n

Document Interaction Controller<\/h2>\n

The document interaction controller<\/a> is the more straightforward option to implement. As the name suggests, not only can it be used for previewing, it can also enable other file interactions, such as opening with another app, copying, or printing.<\/p>\n

To use the document interaction controller, start by creating a class that inherits from UIDocumentInteractionControllerDelegate<\/code><\/a>. While most of the delegate methods are optional, in order to enable previewing you must override the ViewControllerForPreview<\/code> method. This method must return a view controller that the document interaction controller can use as its parent. You can define a constructor with a UIViewController<\/code> parameter so you can pass in the parent view controller:<\/p>\n

public class MyInteractionDelegate : UIDocumentInteractionControllerDelegate\r\n{\r\n    UIViewController parent;\r\n\r\n    public MyInteractionDelegate(UIViewController controller)\r\n    {\r\n        parent = controller;\r\n    }\r\n\r\n    public override UIViewController ViewControllerForPreview(UIDocumentInteractionController controller)\r\n    {\r\n        return parent;\r\n    }\r\n}\r\n<\/pre>\n
When you are ready to present the preview, create a new document interaction controller by using the UIDocumentInteractionController.FromUrl<\/code> method and passing it the path to the file. Then set its Delegate<\/code> property to a new instance of the class above and call PresentPreview<\/code>:<\/p>\n
var previewController = UIDocumentInteractionController.FromUrl(\r\n    NSUrl.FromFilename(\"sampledocs\/gettingstarted.pdf\"));\r\n\r\npreviewController.Delegate = new MyInteractionDelegate(this);\r\npreviewController.PresentPreview(true);\r\n<\/pre>\n
\"Gif<\/a><\/p>\n
Other Interaction Options<\/h3>\n
As mentioned earlier, the document interaction controller offers more than just previews. Calling PresentOptionsMenu<\/code> instead will present a menu with apps installed that can open the file and other options such as copying or printing the file. PresentOpenInMenu<\/code> is similar except it will only show the list of apps that can open the file.<\/p>\n
\"Screenshot<\/a>
Menu options for PresentOptionsMenu (left) and PresentOpenInMenu (right)<\/figcaption><\/figure><\/p>\n
Quick Look Preview Controller<\/h2>\n
Unlike the document interaction controller, the Quick Look preview controller<\/a> can only preview files. It also requires a data source, however, the benefit of this is that it can preview multiple files at the same time.<\/p>\n
To begin, create a class that inherits from QLPreviewControllerDataSource<\/code><\/a>. You will need to override the following methods:<\/p>\n