incromet/android-task-list

Android Local Storage & List Views

• Consume secure REST API wih Retrofit
• Configure and integrate Android local storage using ROOM Persistence library.
• Create a List View using RecyclerView and CardLayout.

Part 1: Consume secure REST API using Bearer Token and Retrofit

1. Add an additional constructor to RetrofitNetwork with an interceptor so we can send our token on every request:

    public RetrofitNetwork( final String token )
       {
           OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
           httpClient.addInterceptor( new Interceptor()
           {
               @Override
               public okhttp3.Response intercept( Chain chain )
                   throws IOException
               {
                   Request original = chain.request();
   
                   Request request = original.newBuilder().header( "Accept", "application/json" ).header( "Authorization",
                                                                                                          "Bearer "
                                                                                                              + token ).method(
                       original.method(), original.body() ).build();
                   return chain.proceed( request );
               }
           } );
           Retrofit retrofit =
               new Retrofit.Builder().baseUrl( BASE_URL ).addConverterFactory( GsonConverterFactory.create() ).client(
                   httpClient.build() ).build();
       }

2. Create TaskService interface with a GET method to retrieve the tasks list.

3. Instantiate the TaskService on the RetrofitNetwork class.

4. Call the method to retrieve the Tasks list from the API and verify it works.

Part 2: Configure Local Storage using Room Library

1. Do the android-persistence codelab until Step 2 - Define Entity Relationships: https://codelabs.developers.google.com/codelabs/android-persistence/

2. Create the structure on your project to have a local database to save the Task and User models.

3. Connect your RetrofitNetwork object with the Database (every time you retrieve the Tasks list you should store the data on the Room Database for offline support).

Part 3: Create a RecyclerView and Adapter to display the Tasks list

1. Modify the content_main.xml layout so it has a RecyclerView component:

   <?xml version="1.0" encoding="utf-8"?>
   <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                                      xmlns:app="http://schemas.android.com/apk/res-auto"
                                                      xmlns:tools="http://schemas.android.com/tools"
                                                      android:layout_width="match_parent"
                                                      android:layout_height="match_parent"
                                                      app:layout_behavior="@string/appbar_scrolling_view_behavior"
                                                      tools:context=".android.ui.activity.MainActivity"
                                                      tools:showIn="@layout/app_bar_main">
   
     <androidx.recyclerview.widget.RecyclerView
         android:id="@+id/recyclerView"
         android:layout_width="match_parent"
         android:layout_height="match_parent"/>
     
   </androidx.constraintlayout.widget.ConstraintLayout>    

2. Create a RecyclerView variable on the MainActivity and bind it with the xml view using findViewById() function.

3. Create a class called TasksAdapter

   public class TasksAdapter
       extends RecyclerView.Adapter<TasksAdapter.ViewHolder>
   {
   
       List<Task> taskList = null;
   
       @NonNull
       @Override
       public ViewHolder onCreateViewHolder( @NonNull ViewGroup parent, int viewType )
       {
           return new ViewHolder( LayoutInflater.from( parent.getContext() ).inflate( R.layout.task_row, parent, false ) );
       }
   
       @Override
       public void onBindViewHolder( @NonNull ViewHolder holder, int position )
       {
           Task task = taskList.get( position );
           //TODO implement update view holder using the task values
       }
   
       @Override
       public int getItemCount()
       {
           return taskList != null ? taskList.size() : 0;
       }
    
        public void updateTasks(List<Task> tasks){
            this.taskList = tasks;
            notifyDataSetChanged();
        }
   
       class ViewHolder
           extends RecyclerView.ViewHolder
       {
           ViewHolder( @NonNull View itemView )
           {
               super( itemView );
           }
       }
   
   }

4. Create the task_row layout (this is the layout that represents a Task).

5. Update your ViewHolder so it holds a reference to the Views used to represent a Task in the task_row layout.

6. Implement the onBindViewHolder function.

7. Create an instance of the TasksAdapter on the MainActivity

8. Add the following function to the MainActivity and call it right after the RecyclerView binding is done:

     private void configureRecyclerView()
       {
           recyclerView.setHasFixedSize( true );
           LinearLayoutManager layoutManager = new LinearLayoutManager( this );
           recyclerView.setAdapter( tasksAdapter );
       }

9. Make a request to retrieve the Tasks list. Once the data is retrieved then call updateTasks method of the of the TasksAdapter instance.
   **Note you should call the updateTasks method from the UI thread using the method runOnUiThread from the MainActivity.

10. Run the application and verify that the Tasks list is loaded correctly.