Image Display Screenlet for Android

Requirements

• Android SDK 4.1 (API Level 16) or above
• Liferay Portal 6.2 CE/EE, Liferay CE Portal 7.0/7.1, Liferay DXP
• Liferay Screens Compatibility app (CE or EE/DXP). This app is preinstalled in Liferay CE Portal 7.0/7.1 and Liferay DXP.

Compatibility

• Android SDK 4.1 (API Level 16) or 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

Views

• Default

The Default View uses an Android ImageView to display the image.

Figure 1: Image Display Screenlet using the Default View.

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

• entryId or classPK

Attributes

Attribute	Data type	Explanation
layoutId	@layout	The layout to use to show the View.
autoLoad	boolean	Whether the image automatically loads when the Screenlet appears in the app’s UI. The default value is true.
entryId	number	The primary key of the image.
classPK	number	The image’s unique identifier.
cachePolicy	string	The offline mode setting. See the Offline section for details.
imageScaleType	number	Lets you set a scale image type like CENTER, CENTER_CROP, CENTER_INSIDE, FIT_CENTER, FIT_END, FIT_START, FIT_XY, MATRIX.
placeHolder	@resource	Image to load until the final image loads.
placeHolderScaleType	number	Lets you set a scale image type for the placeholder like CENTER, CENTER_CROP, CENTER_INSIDE, FIT_CENTER, FIT_END, FIT_START, FIT_XY, MATRIX.

Note that the values for imageScaleType and placeHolderScaleType match those described in Android’s ImageView.ScaleType.

Listener

Because images are assets, Image Display Screenlet delegates its events to a class that implements AssetDisplayListener. This interface lets you implement the following methods:

• onRetrieveAssetSuccess(AssetEntry assetEntry): Called when the Screenlet successfully loads the image.

• error(Exception e, String userAction): Called when an error occurs in the process. The userAction argument distinguishes the specific action in which the error occurred.