Exercise session 6

05.12.2017

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Overview

We’ll create a notes app.

With EditText, Button and RecyclerView

We’ll save the notes to the database.

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On user click we’ll add note to the database

User click on note we will remove it from database

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What is Room?

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Room persistence library provides an abstraction layer over SQLite to allow fluent database access while harnessing the full power of SQLite.

There are 3 major components in Room

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• DataBase - Contains the database holder and serves as the main access point
• Entity - Represents a table within the database.
• DAO - Contains the methods used for accessing the database.

Let’s Begin

You can always use This project as a reference

And Room training Guide can be helpful too.

Step1- Create a new project

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For help go to the lecture slides:goo.gl/9RwRvw

Or

Clone goo.gl/UpAE66

Step2- Add Room dependencies

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Add Room to dependencies in build.gradle(app) file:

implementation "android.arch.persistence.room:runtime:1.0.0"�annotationProcessor "android.arch.persistence.room:compiler:1.0.0"

GitHub commit: https://goo.gl/TfmEpH

Step3- Create Note Entity class

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• Create Note class and mark it with @Entity annotation
• Create id field and mark it as @PrimaryKey(autoGenerate = true)
• Add 2 Strings for the note title and body
• Add getters and setters for the fields.

@Entity�public class Note {� @PrimaryKey(autoGenerate = true)� private int id;

GitHub commit: https://goo.gl/3jE2dd

Step4- Add AppDatabase class

• AppDatabase class must to extend RoomDatabase class
• Annotate your class with @Database(entities = {Note.class}, version = 1)
• You should follow the singleton design pattern when instantiating an AppDatabase object, as each RoomDatabase instance is fairly expensive.
• Add allowMainThreadQueries() for testing purposes. Please note that in real project all interactions with the database must be executed in the background.

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INSTANCE = Room.databaseBuilder(context.getApplicationContext(),� AppDatabase.class, DATABASE_NAME)� .allowMainThreadQueries()� .build();

GitHub commit: https://goo.gl/Hx4BBa

Step5- Add NoteDao interface

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• Create NoteDao interface and mark it with @Dao annotation
• DAO - Data Access Object - is an abstract class or interface that includes methods to define database queries.

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*** Do not forget to add abstract method in AppDatabase that returns NoteDao

public abstract NoteDao noteDao();

GitHub commit: https://goo.gl/gD3TPc

NoteDao - query data

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@Query("SELECT * FROM Note")�List<Note> getAll();��@Query("SELECT * FROM Note WHERE id = :id")�Note getNoteById(int id);

NoteDao - insert row/s

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@Insert(onConflict = OnConflictStrategy.REPLACE)�void insertAll(Note... notes);��@Insert(onConflict = OnConflictStrategy.REPLACE)�void insert(Note note);

NoteDao - delete row

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@Delete�void delete(Note note);

Step6 - Add RecyclerView

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• Add RecylerView. For help go to the lecture slides.
• Create adapter that would work with List of Note objects
• Create some fake data to test your RecyclerView

mNotesAdapter = new NotesAdapter(this, getNoteList());�recyclerView.setAdapter(mNotesAdapter);

private List<Note> getNoteList() {� List<Note> list = new ArrayList<>();� list.add(createNote("Title 1", "Body 1"));� list.add(createNote("Title 2", "Body 2"));� list.add(createNote("Title 3", "Body 3"));� return list;�}

private Note createNote(String title, String body) {� Note note = new Note();� note.setTitle(title);� note.setBody(body);� return note;�}

GitHub commit: https://goo.gl/wbJstm

Step7- Add fake data to DB and use it in adapter

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private List<Note> getNoteList() {� AppDatabase.getInstance(this).noteDao().insertAll(� createNote("Title 1", "Body 1"),� createNote("Title 2", "Body 2"),� createNote("Title 3", "Body 3")� );� return AppDatabase.getInstance(this).noteDao().getAll();�}

GitHub commit: https://goo.gl/ot6o3h

Step8 - Delete notes from DB on item click

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• Delete row with: AppDatabase.getInstance(this).noteDao().delete(note);
• Remove item from the list and notify adapter

public void onClick(View view) {� int position = (int) view.getTag();� Note note = mNoteList.get(position);� mListener.onDeleteNote(note);� mNoteList.remove(note);� notifyItemRemoved(position);� notifyItemRangeChanged(position, mNoteList.size());�}

GitHub commit: https://goo.gl/SYuyfb

Step9 - Remove fake data

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GitHub commit: https://goo.gl/kTpB9b

Step10- Add adding note UI elements

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• Add EditText for Title and for Body of the note
• Add Button “Add Note”.

GitHub commit: https://goo.gl/RVhCxD

Step11- Add note to DB

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When user click on “Add note” button get inputs from EditTexts and save them to the database

AppDatabase.getInstance(this).noteDao().insert(note);

GitHub commit: https://goo.gl/k8m3QQ

Step12- Update the list when new note is added

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MainActivity

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NotesAdapter

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List<Note> updatedList = getNoteList();�mNotesAdapter.updateList(updatedList);� � �public void updateList(List<Note> updatedList) {� mNoteList = updatedList;� notifyDataSetChanged();�}

GitHub commit: https://goo.gl/946ZCe

DONE?

That’s amazing! Good for you!!

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If you have even a small question- don’t forget to ask the mentors:

At the class or on Slack.

Kudos!!

You’re all done with exercise 6!

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See you next time!