Getting Started with Guestbook List Screenlet

Before creating a Screenlet, you should know how you’ll use it. If you plan to use it in only one app, then you can create it in that app’s project. If you need to use it in several apps, however, then it’s best to create it in a separate project for redistribution. For information on creating Screenlets for redistribution, see the tutorial Packaging Your Android Screenlets.

Since you’ll use Guestbook List Screenlet in only this app, you can create it in a new package inside the app’s project. Create this package now:

1. In Android Studio, right click the java folder and select New → Package.

2. Select …/app/src/main/java as the destination directory, and click OK.

3. Enter com.liferay.docs.guestbooklistscreenlet as the package’s name and click OK. Android Studio lists the new package alongside the package that contains the app’s activity and fragment (liferayguestbook). If it doesn’t appear at first, you may need to collapse and reopen the java folder.

Figure 1: Guestbook List Screenlet's new package is highlighted.

Before getting started, you should understand how pagination works in in list Screenlets.

Pagination

To ensure that users can scroll smoothly through large lists of items, list Screenlets support fluent pagination. Support for this is built into the list Screenlet framework. You’ll see this as you construct your list Screenlet. For example, several methods have parameters for the start row and end row of a page in the list.

Now you’re ready to begin!

Creating the Model Class for Guestbooks

Entities come back from Liferay Portal in JSON. To work with these results efficiently in your app, you must convert them to model objects that represent the entity in the portal. Although Screens’s BaseListInteractor transforms the JSON entities into Map objects for you, you still must convert these into proper entity objects for use in your app. You’ll do this via a model class.

The model class you’ll create for Guestbook List Screenlet, GuestbookModel, creates GuestbookModel objects that represent guestbooks retrieved from the Guestbook portlet. You’ll create this model class in a separate package outside of the guestbooklistscreenlet package. In this case, it makes sense to organize your code this way because other Screenlets may also use the model class. For example, if a Screenlet that edits guestbooks existed, it would also need GuestbookModel objects. Putting the model class in a separate package makes it clear that this class doesn’t belong exclusively to a single Screenlet.

Follow these steps to create GuestbookModel:

1. Create a new package called model inside the com.liferay.docs package.

2. Inside this new model package, create a new class called GuestbookModel.

3. Replace GuestbookModel’s contents with this code:

   package com.liferay.docs.model;
   
   import android.os.Parcel;
   import android.os.Parcelable;
   
   import java.util.Date;
   import java.util.Map;
   
   public class GuestbookModel implements Parcelable {
   
       private Map values;
       private long guestbookId;
       private long groupId;
       private long companyId;
       private long userId;
       private String userName;
       private long createDate;
       private long modifiedDate;
       private String name;
   
       public static final Creator<GuestbookModel> CREATOR = new Creator<GuestbookModel>() {
           @Override
           public GuestbookModel createFromParcel(Parcel in) {
               return new GuestbookModel(in);
           }
   
           @Override
           public GuestbookModel[] newArray(int size) {
               return new GuestbookModel[size];
           }
       };
   
       public GuestbookModel() {
           super();
       }
   
       protected GuestbookModel(Parcel in) {
           guestbookId = in.readLong();
           groupId = in.readLong();
           companyId = in.readLong();
           userId = in.readLong();
           userName = in.readString();
           createDate = in.readLong();
           modifiedDate = in.readLong();
           name = in.readString();
       }
   
       public GuestbookModel(Map<String, Object> stringObjectMap) {
           values = stringObjectMap;
           guestbookId =  ((Integer) stringObjectMap.get("guestbookId")).longValue();
           groupId = ((Integer) stringObjectMap.get("groupId")).longValue();
           companyId = ((Integer) stringObjectMap.get("companyId")).longValue();
           userId = ((Integer) stringObjectMap.get("userId")).longValue();
           userName = (String) stringObjectMap.get("userName");
           createDate = (long) stringObjectMap.get("createDate");
           modifiedDate = (long) stringObjectMap.get("modifiedDate");
           name = (String) stringObjectMap.get("name");
       }
   
       @Override
       public void writeToParcel(Parcel dest, int flags) {
           dest.writeLong(guestbookId);
           dest.writeLong(groupId);
           dest.writeLong(companyId);
           dest.writeLong(userId);
           dest.writeString(userName);
           dest.writeLong(createDate);
           dest.writeLong(modifiedDate);
           dest.writeString(name);
       }
   
       @Override
       public int describeContents() {
           return 0;
       }
   
       public long getGuestbookId() {
           return guestbookId;
       }
   
       public long getGroupId() {
           return groupId;
       }
   
       public long getCompanyId() {
           return companyId;
       }
   
       public long getUserId() {
           return userId;
       }
   
       public String getUserName() {
           return userName;
       }
   
       public Date getCreateDate() {
           return new Date(createDate);
       }
   
       public Date getModifiedDate() {
           return new Date(modifiedDate);
       }
   
       public String getName() {
           return name;
       }
   
       public Map getValues() {
           return values;
       }
   
       public void setValues(Map values) {
           this.values = values;
       }
   }
   

This class creates GuestbookModel objects that represent the Guestbook portlet’s Guestbook objects. The constructor with the Map<String, Object> argument does the heavy lifting. Following a successful Mobile SDK call, the list Screenlet framework’s BaseListInteractor class returns this Map, which contains the data of a guestbook retrieved from the portlet. To get the guestbook’s data from the Map, the constructor uses the get method with each parameter of the portlet’s Guestbook entity. To see how the portlet defines these parameters, see the Liferay MVC Learning Path article on Service Builder. For now, the only parameters you really need in GuestbookModel are guestbookId and name. Because you might need the rest later, however, it’s best to add all of them now.

Besides the getters and setter, the remaining code in GuestbookModel implements Android’s Parcelable interface. For more information on this, see Android’s documentation on Parcelable.

Great! Now you have a model class for guestbooks. Next, you’ll create the Screenlet’s UI.