Creating the Interactor

A Screenlet’s Interactor makes the service call to retrieve the data you need from a Liferay instance. An Interactor is made up of several components:

  1. The event class. This class lets you handle communication between the Screenlet’s components via event objects that contain the server call’s results. Screens uses the EventBus library for this. Screens supplies the BasicEvent class and BaseListEvent class for communicating JSONObject and JSONArray results within Screenlets, respectively. You can create your own event classes by extending BasicEvent. You should create your own event classes when you must communicate objects other than JSONObject or JSONArray. The example Add Bookmark Screenlet only needs to communicate JSONObject instances, so it uses BasicEvent.

  2. The listener interface. This defines the methods the app developer needs to respond to the Screenlet’s behavior. For example, Login Screenlet’s listener defines the onLoginSuccess and onLoginFailure methods. Screens calls these methods when login succeeds or fails, respectively. By implementing these methods in the activity or fragment class that contains the Screenlet, the app developer can respond to login success and failure. Similarly, the example Add Bookmark Screenlet’s listener interface defines two methods: one for responding to the Screenlet’s failure to add a bookmark and one for responding to its success to add a bookmark:

     public interface AddBookmarkListener {
         void onAddBookmarkFailure(Exception exception);
         void onAddBookmarkSuccess();
  3. The Interactor class. This class must extend Screens’s BaseRemoteInteractor with your listener and event as type arguments. The listener lets the Interactor class send the server call’s results to any classes that implement the listener. In the implementation of the method that makes the server call, the execute method, you must use the Mobile SDK to make an asynchronous service call. This means you must get a session and then make the server call. You make the server call by creating an instance of the Mobile SDK service (e.g., BookmarksEntryService) that can call the Liferay service you need and then making the call. The Interactor class must also process the event object that contains the call’s results and then notify the listener of those results. You do this by implementing the onSuccess and onFailure methods to invoke the corresponding getListener() methods.

    For example, the AddBookmarkInteractor class is Add Bookmark Screenlet’s Interactor class. This class implements the execute method, which adds a bookmark to a folder in a Liferay instance’s Bookmarks portlet. This method first validates the bookmark’s URL and folder. It then calls the getJSONObject method to add the bookmark, and concludes by returning a new BasicEvent object created from the JSONObject. The if statement in the getJSONObject method checks the Liferay version so it can create the appropriate BookmarksEntryService instance needed to make the server call. Regardless of the Liferay version, the getSession() method retrieves the existing session created by Login Screenlet upon successful login. The session’s addEntry method makes the server call. The Screenlet calls the onSuccess or onFailure method to notify the listener of the server call’s success or failure, respectively. In either case, the BasicEvent object contains the server call’s results. Since this Screenlet doesn’t retrieve anything from the server, however, there’s no need to process the BasicEvent object in the onSuccess method; calling the listener’s onAddBookmarkSuccess method is sufficient. Here’s the complete code for AddBookmarkInteractor:

     public class AddBookmarkInteractor extends BaseRemoteInteractor<AddBookmarkListener, BasicEvent> {
         public BasicEvent execute(Object[] args) throws Exception {
             String url = (String) args[0];
             String title = (String) args[1];
             long folderId = (long) args[2];
             validate(url, folderId);
             JSONObject jsonObject = getJSONObject(url, title, folderId);
             return new BasicEvent(jsonObject);
         public void onSuccess(BasicEvent event) throws Exception {
         public void onFailure(BasicEvent event) {
         private void validate(String url, long folderId) {
             if (url == null || url.isEmpty() || !URLUtil.isValidUrl(url)) {
                 throw new IllegalArgumentException("Invalid url");
             } else if (folderId == 0) {
                 throw new IllegalArgumentException("folderId not set");
         private JSONObject getJSONObject(String url, String title, long folderId) throws Exception {
             if (LiferayServerContext.isLiferay7()) {
                 return new BookmarksEntryService(getSession()).addEntry(LiferayServerContext.getGroupId(), 
                     folderId, title, url, "", null);
             } else {
                 return new
                     getSession()).addEntry(LiferayServerContext.getGroupId(), folderId, title, url, "", null);

Sweetness! Your Screenlet’s Interactor is done. Next, you’ll create the Screenlet class.

Creating the UI

Defining the Attributes

Creating the Screenlet Class

Packaging Your Screenlets

« Creating the UIDefining the Attributes »
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