Image Gallery 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 Gallery Screenlet shows a list of images from a Documents and Media folder in a Liferay instance. You can also use Image Gallery Screenlet to upload images to and delete images from the same folder. The Screenlet implements fluent pagination with configurable page size, and supports i18n in asset values.

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
DLAppService	getFileEntries	Load
DLAppService	getFileEntriesCount
DLAppService	addFileEntry	Upload
DLAppService	deleteFileEntry	Delete

Module

• None

Views

The included Views use a standard Android RecyclerView to show the scrollable list. Other custom Views may use a different component, such as ViewPager or others, to show the items.

This Screenlet has three different Views:

1. Grid (default)
2. Slideshow
3. List

Figure 1: Image Gallery Screenlet using the Grid, Slideshow, and List Views.

Offline

This Screenlet supports offline mode so it can function without a network connection when loading or uploading images (deleting images while offline is unsupported). For more information on how offline mode works, see the tutorial on its architecture. This Screenlet supports the REMOTE_ONLY, CACHE_ONLY, REMOTE_FIRST, and CACHE_FIRST offline mode policies.

These policies take the following actions when loading images from a Liferay instance:

Policy	What happens	When to use
REMOTE_ONLY	The Screenlet loads the list 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 list, it stores the data 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 list from the local cache. If the list 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 list from the Liferay instance. If this succeeds, the Screenlet shows the list to the user and stores it in the local cache for later use. If a connection issue occurs, the Screenlet retrieves the list from the local cache. If the list 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 list from the local cache. If the list 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.

These policies take the following actions when uploading an image to a Liferay instance:

Policy	What happens	When to use
REMOTE_ONLY	The Screenlet sends the image to the Liferay instance. If a connection issue occurs, the Screenlet uses the delegate to notify the developer about the error, but it also discards the image.	Use this policy to make sure the Liferay instance always has the most recent version of the image.
CACHE_ONLY	The Screenlet stores the image in the local cache.	Use this policy when you need to save the image locally, but don’t want to update the image in the Liferay instance (delete or add image).
REMOTE_FIRST	The Screenlet sends the image to the Liferay instance. If this succeeds, it also stores the image in the local cache for later use. If a connection issue occurs, the Screenlet stores the image in the local cache and sends it to the Liferay instance when the connection is re-established.	Use this policy when you need to make sure the Screenlet sends the image to the Liferay instance as soon as the connection is restored.
CACHE_FIRST	The Screenlet stores the image in the local cache and then attempts to send it to the Liferay instance. If a connection issue occurs, the Screenlet sends the image to the Liferay instance when the connection is re-established.	Use this policy when you need to make sure the Screenlet sends the image to the Liferay instance as soon as the connection is restored. Compared to REMOTE_FIRST, this policy always stores the image in the cache. The REMOTE_FIRST policy only stores the image in the event of a network error.

Required Attributes

• folderId
• repositoryId

Attributes

Attribute	Data type	Explanation
repositoryId	number	The ID of the Liferay instance’s Documents and Media repository that contains the image gallery. If you’re using a site’s default Documents and Media repository, then the repositoryId matches the site ID (groupId).
folderId	number	The ID of the Documents and Media repository folder that contains the image gallery. When accessing the folder in your browser, the folderId is at the end of the URL.
cachePolicy	string	The offline mode setting. See the Offline section for details.
firstPageSize	number	The number of items to display on the first page. The default value is 50.
pageSize	number	The number of items to display on second and subsequent pages. The default value is 25.
mimeTypes	string	The comma-separated list of MIME types for the Screenlet to support.
autoLoad	boolean	Whether the list automatically loads when the Screenlet appears in the app’s UI. The default value is true.
layoutId	@layout	The layout to use to show the View.
obcClassName	string	The name of the OrderByComparator class to use to sort the results. Omit this property if you don’t want to sort the results. Note that you can only use comparator classes that extend OrderByComparator<DLFileEntry>. Liferay contains no such comparator classes. You must therefore create your own by extending OrderByComparator<DLFileEntry>. To see examples of some comparator classes that extend other Document Library classes, click here.

Methods

Method	Return	Explanation
loadPage(pageNumber)	void	Starts the request to load the specified page of images. The page is shown when the response is received.

Listener

Image Gallery Screenlet delegates some events to an object or class that implements its ImageGalleryListener interface. This interface extends the BaseListListener interface. Therefore, Image Gallery Screenlet’s listener methods are as follows:

• onListPageFailed(int startRow, Exception e): Called when the server call to retrieve a page of items fails. This method’s arguments include the Exception generated when the server call fails.

• onListPageReceived(int startRow, int endRow, List<Record> records, int rowCount): Called when the server call to retrieve a page of items succeeds. Note that this method may be called more than once; once for each page received. Because startRow and endRow change for each page, a startRow of 0 corresponds to the first item on the first page.

• onListItemSelected(Record records, View view): Called when an item is selected in the list. This method’s arguments include the selected list item (Record).

• onImageEntryDeleted(long imageEntryId): Called when an item in the list is deleted.

• onImageUploadStarted(String picturePath, String title, String description, String changelog): Called when an item is prepared for upload.

• onImageUploadProgress(int totalBytes, int totalBytesSent): Called when an item is uploading.

• onImageUploadEnd(ImageEntry entry): Called when an item finishes uploading.

• showUploadImageView(String actionName, String picturePath, int screenletId): Called when the View for uploading an image is instantiated. The default behavior is to show the default View in a dialog. To retain this behavior, all this method needs to do is return false. To change the default behavior, use the initializeUploadView method to initialize a custom View that extends BaseDetailUploadView. Then return true to prevent the Screenlet from executing the default behavior. For example, the following sample implementation uses initializeUploadView to initialize the custom View instance uploadDetailView. It then performs a custom UI action (uploadImageCard.goRight()) and returns true:

    @Override
    public boolean showUploadImageView(String actionName, String picturePath, int screenletId) {
        uploadDetailView.initializeUploadView(actionName, picturePath, screenletId);
        uploadImageCard.goRight();
  
        return true;
    }
  

• provideImageUploadDetailView(): Called when the Screenlet provides the image upload View. To inflate the default View, return 0 in this method. Alternatively, display this View with a custom layout by returning its layout ID. Such a layout must have DefaultUploadDetailView as its root class.

• 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.