Image Display Screenlet for iOS

Requirements

• Xcode 9.0
• iOS 11 SDK
• Liferay Portal 6.2 (CE or EE), Liferay 7.0 CE, Liferay DXP
• Liferay Screens Compatibility plugin (for Liferay Portal CE or Liferay Portal EE).

Compatibility

• iOS 9 and above

Xamarin Requirements

• Visual Studio 7.2
• Mono .NET framework 5.4.1.6

Features

Image Display Screenlet displays an image file from a Liferay instance’s Documents and Media Library.

JSON Services Used

Screenlets in Liferay Screens call JSON web services in the portal. This Screenlet calls the following services and methods.

Service	Method	Notes
ScreensassetentryService (Screens compatibility plugin)	getAssetEntry	With entryId
ScreensassetentryService (Screens compatibility plugin)	getAssetEntry	With classPK and className
ScreensassetentryService (Screens compatibility plugin)	getAssetEntries	With entryQuery
ScreensassetentryService (Screens compatibility plugin)	getAssetEntries	With companyId, groupId, and portletItemName

Module

• None

Themes

• Default

The Default Theme uses an iOS UIImageView for displaying the image.

Figure 1: Image Display Screenlet using the Default Theme.

Offline

This Screenlet supports offline mode so it can function without a network connection. For more information on how offline mode works, see the tutorial on its architecture. Here are the offline mode policies that you can use with this Screenlet:

Policy	What happens	When to use
remote-only	The Screenlet loads the data from the Liferay instance. If a connection issue occurs, the Screenlet uses the listener to notify the developer about the error. If the Screenlet successfully loads the data, it stores it in the local cache for later use.	Use this policy when you always need to show updated data, and show nothing when there’s no connection.
cache-only	The Screenlet loads the data from the local cache. If the data isn’t there, the Screenlet uses the listener to notify the developer about the error.	Use this policy when you always need to show local data, without retrieving remote information under any circumstance.
remote-first	The Screenlet loads the data from the Liferay instance. If this succeeds, the Screenlet shows the data to the user and stores it in the local cache for later use. If a connection issue occurs, the Screenlet retrieves the data from the local cache. If the data doesn’t exist there, the Screenlet uses the listener to notify the developer about the error.	Use this policy to show the most recent version of the data when connected, but show an outdated version when there’s no connection.
cache-first	The Screenlet loads the data from the local cache. If the data isn’t there, the Screenlet requests it from the Liferay instance and notifies the developer about any errors that occur (including connectivity errors).	Use this policy to save bandwidth and loading time in case you have local (but probably outdated) data.

Required Attributes

• assetEntryId

If you don’t use assetEntryId, you must use these attributes:

• className
• classPK

Attributes

Attribute	Data type	Explanation
assetEntryId	number	The primary key of the image.
className	string	The image’s fully qualified class name. Since files in a Documents and Media Library are DLFileEntry objects, their className is com.liferay.portlet.documentlibrary.model.DLFileEntry. The className and classPK attributes are required to instantiate the Screenlet.
classPK	number	The image’s unique identifier. The className and classPK attributes are required to instantiate the Screenlet.
autoLoad	boolean	Whether the image automatically loads when the Screenlet appears in the app’s UI. The default value is true.
offlinePolicy	string	The offline mode setting. The default value is remote-first. See the Offline section for details.

Delegate

Because images are files, Image Display Screenlet delegates its events to an object that conforms to the FileDisplayScreenletDelegate protocol. This protocol lets you implement the following methods:

• - screenlet:onFileAssetResponse:: Called when the Screenlet receives the image file.

• - screenlet:onFileAssetError:: Called when an error occurs in the process. The NSError object describes the error.