Android Room Database Example

Hi everyone, in this post we will learn about another architectural component of android which is Room Persistence Library. In this android room database example, we will learn how to use room for handling our SQLite database.

Here is a new Android Room Database Example using Kotlin.

This is a video tutorial series and throughout this we will build a basic notes application using Room persistence library.

Table of Contents

1 What is Room?
2 Components of Room
3 Android Room Database Example
4 Todo App
5 Android Room Database Example Source Code

What is Room?

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

Basically, with the help of room we can quickly create sqlite databases and perform the operations like create, read, update and delete. Room makes everything very easy and quick.

Components of Room

We have 3 components of room.

Entity: Instead of creating the SQLite table, we will create the Entity. Entity is nothing but a model class annotated with @Entity. The variables of this class is our columns, and the class is our table.
Database: It is an abstract class where we define all our entities.
DAO: Stands for Data Access Object. It is an interface that defines all the operations that we need to perform in our database.

I will not go to further theoretical details of Room. But you can check this link for more details.

So what we are going to do is, we are going to create a To Do application using SQLite and in this application we will learn how we can use Room for handling SQLite.

Creating a new Project

So create a new project in Android Studio. I have named this project as My ToDo.
The first thing that we will do is we will add all the required dependencies.

Adding Dependencies

Come inside app level build.gradle file and add the following dependencies.

dependencies {

//define versions

def support_version = "27.0.2"

def room_version = "1.1.1"

implementation fileTree(include: ['*.jar'], dir: 'libs')

implementation "com.android.support:appcompat-v7:$support_version"

implementation 'com.android.support.constraint:constraint-layout:1.1.2'

testImplementation 'junit:junit:4.12'

androidTestImplementation 'com.android.support.test:runner:1.0.2'

androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

//add these libraries

//support design

implementation "com.android.support:design:$support_version"

//card view

implementation "com.android.support:cardview-v7:$support_version"

//recyclerview

implementation "com.android.support:recyclerview-v7:$support_version"

//room

implementation "android.arch.persistence.room:runtime:$room_version"

annotationProcessor "android.arch.persistence.room:compiler:$room_version"

testImplementation "android.arch.persistence.room:testing:$room_version"

}

After adding the above dependencies sync your project and you are good to go.

Creating Activities

We already have a MainActivity created, other than this MainActivity we need, AddTaskActivity and UpdateTaskActivity.
So create 2 more activities and name them AddTaskActivity and UpdateTaskActivity.

MainActivity

Before designing the activities define these colors in your colors.xml.

<?xml version="1.0" encoding="utf-8"?>

</resources>

Come inside activity_main.xml and add the following xml code.

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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"

android:padding="8dp"

tools:context=".MainActivity">

<android.support.v7.widget.RecyclerView

android:id="@+id/recyclerview_tasks"

android:layout_width="match_parent"

android:layout_height="match_parent" />

<android.support.design.widget.FloatingActionButton

android:id="@+id/floating_button_add"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_alignParentRight="true"

android:layout_margin="8dp"

android:backgroundTint="@color/colorPrimaryDark"

android:src="@drawable/ic_add"

android:tint="@color/colorLight"

app:fabSize="normal" />

</RelativeLayout>

In our main activity we will display all the added task, and an add button at the bottom from where user can add a new task.
For displaying all the added task we defined RecyclerView and FloatingActionButton for adding a new task.

AddTaskActivity

From this activity we will add a new task to our application. So we need an interface like this.

For designing the above screen write the following code.

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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"

tools:context=".AddTaskActivity">

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_centerVertical="true"

android:orientation="vertical"

android:padding="16dp">

<TextView

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_margin="15dp"

android:text="Add a Task"

android:textAlignment="center"

android:textAppearance="@style/Base.TextAppearance.AppCompat.Headline" />

<EditText

android:id="@+id/editTextTask"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="task?" />

<EditText

android:id="@+id/editTextDesc"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="description..." />

<EditText

android:id="@+id/editTextFinishBy"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="finish by?" />

<Button

android:id="@+id/button_save"

android:layout_width="200dp"

android:layout_height="wrap_content"

android:layout_gravity="center_horizontal"

android:layout_marginTop="15dp"

android:background="@color/colorPrimary"

android:text="Save"

android:textAllCaps="false"

android:textColor="@color/colorLight" />

</LinearLayout>

</RelativeLayout>

UpdateTaskActivity

Finally go inside activity_update_task.xml and write the following xml code.

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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"

tools:context=".UpdateTaskActivity">

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_centerVertical="true"

android:orientation="vertical"

android:padding="16dp">

<TextView

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_margin="15dp"

android:text="Update Task"

android:textAlignment="center"

android:textAppearance="@style/Base.TextAppearance.AppCompat.Headline" />

<EditText

android:id="@+id/editTextTask"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="task?" />

<EditText

android:id="@+id/editTextDesc"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="description..." />

<EditText

android:id="@+id/editTextFinishBy"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="finish by?" />

<CheckBox

android:id="@+id/checkBoxFinished"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Mark as finished" />

<Button

android:id="@+id/button_update"

android:layout_width="200dp"

android:layout_height="wrap_content"

android:layout_gravity="center_horizontal"

android:layout_marginTop="15dp"

android:background="@color/colorPrimary"

android:text="Update"

android:textAllCaps="false"

android:textColor="@color/colorLight" />

<Button

android:id="@+id/button_delete"

android:layout_width="200dp"

android:layout_height="wrap_content"

android:layout_gravity="center_horizontal"

android:layout_marginTop="15dp"

android:background="@color/colorRed"

android:text="Delete"

android:textAllCaps="false"

android:textColor="@color/colorLight" />

</LinearLayout>

</RelativeLayout>

Tasks RecyclerView Layout

We will display all the tasks added in a RecyclerView, and for this we need one more layout file. So create a layout file and name it recyclerview_tasks.xml and write the following xml code inside.

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="wrap_content">

<android.support.v7.widget.CardView

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginBottom="3dp">

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical"

android:padding="7dp">

<TextView

android:id="@+id/textViewStatus"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginBottom="5dp"

android:background="@color/colorPrimaryDark"

android:text="Completed"

android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium"

android:textColor="@color/colorLight"

android:textStyle="bold" />

<TextView

android:id="@+id/textViewTask"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Go Bring Eggs"

android:textAppearance="@style/Base.TextAppearance.AppCompat.Headline" />

<TextView

android:id="@+id/textViewDesc"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Bring 6 eggs from super market"

android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

<TextView

android:id="@+id/textViewFinishBy"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="5pm today"

android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium" />

</LinearLayout>

</android.support.v7.widget.CardView>

</RelativeLayout>

Creating Entity

Now here come the main thing, for every table that we need we need to create an entity. And for this application we need a single entity.

So create a class named Task.java and write the following code.

package net.simplifiedcoding.mytodo;

import android.arch.persistence.room.ColumnInfo;

import android.arch.persistence.room.Entity;

import android.arch.persistence.room.PrimaryKey;

import java.io.Serializable;

@Entity

public class Task implements Serializable {

@PrimaryKey(autoGenerate = true)

private int id;

@ColumnInfo(name = "task")

private String task;

@ColumnInfo(name = "desc")

private String desc;

@ColumnInfo(name = "finish_by")

private String finishBy;

@ColumnInfo(name = "finished")

private boolean finished;

* Getters and Setters

* */

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getTask() {

return task;

}

public void setTask(String task) {

this.task = task;

}

public String getDesc() {

return desc;

}

public void setDesc(String desc) {

this.desc = desc;

}

public String getFinishBy() {

return finishBy;

}

public void setFinishBy(String finishBy) {

this.finishBy = finishBy;

}

public boolean isFinished() {

return finished;

}

public void setFinished(boolean finished) {

this.finished = finished;

}

As you can see in the above code we have annotated the class with @Entity this is our table, and for the column id we have used @PrimaryKey(autoGenerate = true) this means this id will be auto increment, for other columns we used @ColumnInfo(name = “columnname”)

Creating Dao

Now we need the Dao (Data Access Object). So create an interface named TaskDao.java and write the following code.

@Dao

public interface TaskDao {

@Query("SELECT * FROM task")

List<Task> getAll();

@Insert

void insert(Task task);

@Delete

void delete(Task task);

@Update

void update(Task task);

}

You can see above we defined all the methods needed for the Create, Read, Update and Delete operation.

Creating Database

Now create one more class and name it AppDatabase, and write the following code inside the class.

package net.simplifiedcoding.mytodo;

import android.arch.persistence.room.Database;

import android.arch.persistence.room.RoomDatabase;

@Database(entities = {Task.class}, version = 1)

public abstract class AppDatabase extends RoomDatabase {

public abstract TaskDao taskDao();

}

In the above class we define all the entities and the database version.

Database Client

Creating AppDatabase’s object is expensive so we will create a single instance of it.
Create a class named DatabaseClient and write the following code.

package net.simplifiedcoding.mytodo;

import android.arch.persistence.room.Room;

import android.content.Context;

public class DatabaseClient {

private Context mCtx;

private static DatabaseClient mInstance;

//our app database object

private AppDatabase appDatabase;

private DatabaseClient(Context mCtx) {

this.mCtx = mCtx;

//creating the app database with Room database builder

//MyToDos is the name of the database

appDatabase = Room.databaseBuilder(mCtx, AppDatabase.class, "MyToDos").build();

}

public static synchronized DatabaseClient getInstance(Context mCtx) {

if (mInstance == null) {

mInstance = new DatabaseClient(mCtx);

}

return mInstance;

}

public AppDatabase getAppDatabase() {

return appDatabase;

}

Adding a Task

Now lets perform the create operation, which is adding a task to the database.

Come inside AddTaskActivity and write the following code.

package net.simplifiedcoding.mytodo;

import android.content.Intent;

import android.os.AsyncTask;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.EditText;

import android.widget.Toast;

public class AddTaskActivity extends AppCompatActivity {

private EditText editTextTask, editTextDesc, editTextFinishBy;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_add_task);

editTextTask = findViewById(R.id.editTextTask);

editTextDesc = findViewById(R.id.editTextDesc);

editTextFinishBy = findViewById(R.id.editTextFinishBy);

findViewById(R.id.button_save).setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

saveTask();

}

});

}

private void saveTask() {

final String sTask = editTextTask.getText().toString().trim();

final String sDesc = editTextDesc.getText().toString().trim();

final String sFinishBy = editTextFinishBy.getText().toString().trim();

if (sTask.isEmpty()) {

editTextTask.setError("Task required");

editTextTask.requestFocus();

return;

}

if (sDesc.isEmpty()) {

editTextDesc.setError("Desc required");

editTextDesc.requestFocus();

return;

}

if (sFinishBy.isEmpty()) {

editTextFinishBy.setError("Finish by required");

editTextFinishBy.requestFocus();

return;

}

class SaveTask extends AsyncTask<Void, Void, Void> {

@Override

protected Void doInBackground(Void... voids) {

//creating a task

Task task = new Task();

task.setTask(sTask);

task.setDesc(sDesc);

task.setFinishBy(sFinishBy);

task.setFinished(false);

//adding to database

DatabaseClient.getInstance(getApplicationContext()).getAppDatabase()

.taskDao()

.insert(task);

return null;

}

@Override

protected void onPostExecute(Void aVoid) {

super.onPostExecute(aVoid);

finish();

startActivity(new Intent(getApplicationContext(), MainActivity.class));

Toast.makeText(getApplicationContext(), "Saved", Toast.LENGTH_LONG).show();

}

SaveTask st = new SaveTask();

st.execute();

}

The above code is very simple, we created an AsyncTask to perform our operation because if we will try to perform the database operation in main thread it will crash our application.
For saving the task we just created the object and called the insert method that we created in our TaskDao interface.
You can try testing this but first you need to open this activity and for this you need to code the open functionality in the MainActivity. So what you have to do to test it is, attach a click listener on the add button that we have created in MainActivity and open AddTaskActivity when the add button is clicked.

Reading All Tasks

Now we will read the saved task from the database, and we will display it on the RecyclerView.

RecyclerView Adapter

Before going further, let’s first create our adapter. So create a class named TasksAdapter and write the following code. If you don’t know about RecyclerView then you can check this Android RecyclerView Tutorial.

package net.simplifiedcoding.mytodo;

import android.content.Context;

import android.content.Intent;

import android.support.v7.widget.RecyclerView;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.TextView;

import java.util.List;

public class TasksAdapter extends RecyclerView.Adapter<TasksAdapter.TasksViewHolder> {

private Context mCtx;

private List<Task> taskList;

public TasksAdapter(Context mCtx, List<Task> taskList) {

this.mCtx = mCtx;

this.taskList = taskList;

}

@Override

public TasksViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

View view = LayoutInflater.from(mCtx).inflate(R.layout.recyclerview_tasks, parent, false);

return new TasksViewHolder(view);

}

@Override

public void onBindViewHolder(TasksViewHolder holder, int position) {

Task t = taskList.get(position);

holder.textViewTask.setText(t.getTask());

holder.textViewDesc.setText(t.getDesc());

holder.textViewFinishBy.setText(t.getFinishBy());

if (t.isFinished())

holder.textViewStatus.setText("Completed");

else

holder.textViewStatus.setText("Not Completed");

}

@Override

public int getItemCount() {

return taskList.size();

}

class TasksViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

TextView textViewStatus, textViewTask, textViewDesc, textViewFinishBy;

public TasksViewHolder(View itemView) {

super(itemView);

textViewStatus = itemView.findViewById(R.id.textViewStatus);

textViewTask = itemView.findViewById(R.id.textViewTask);

textViewDesc = itemView.findViewById(R.id.textViewDesc);

textViewFinishBy = itemView.findViewById(R.id.textViewFinishBy);

itemView.setOnClickListener(this);

}

@Override

public void onClick(View view) {

Task task = taskList.get(getAdapterPosition());

Intent intent = new Intent(mCtx, UpdateTaskActivity.class);

intent.putExtra("task", task);

mCtx.startActivity(intent);

}

In the above code we also attached a click listener to our itemView so that we can fire an event when a task is clicked. When a task is clicked we are opening the UpdateTaskActivity and we are also passing the selected task using intent.

Reading Tasks

Come inside MainActivity and write the following code.

package net.simplifiedcoding.mytodo;

import android.arch.persistence.room.Room;

import android.content.Intent;

import android.os.AsyncTask;

import android.support.design.widget.FloatingActionButton;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.support.v7.widget.LinearLayoutManager;

import android.support.v7.widget.RecyclerView;

import android.view.View;

import android.widget.Toast;

import java.util.ArrayList;

import java.util.List;

public class MainActivity extends AppCompatActivity {

private FloatingActionButton buttonAddTask;

private RecyclerView recyclerView;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

recyclerView = findViewById(R.id.recyclerview_tasks);

recyclerView.setLayoutManager(new LinearLayoutManager(this));

buttonAddTask = findViewById(R.id.floating_button_add);

buttonAddTask.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

Intent intent = new Intent(MainActivity.this, AddTaskActivity.class);

startActivity(intent);

}

});

getTasks();

}

private void getTasks() {

class GetTasks extends AsyncTask<Void, Void, List<Task>> {

@Override

protected List<Task> doInBackground(Void... voids) {

List<Task> taskList = DatabaseClient

.getInstance(getApplicationContext())

.getAppDatabase()

.taskDao()

.getAll();

return taskList;

}

@Override

protected void onPostExecute(List<Task> tasks) {

super.onPostExecute(tasks);

TasksAdapter adapter = new TasksAdapter(MainActivity.this, tasks);

recyclerView.setAdapter(adapter);

}

GetTasks gt = new GetTasks();

gt.execute();

}

The code is very simple, we just called the getAll() method that we created inside our TaskDao to get all the stored tasks from the database.
Then we are displaying the read tasks to a RecyclerView.

Updating and Deleting Task

Now finally the Update and Delete operation we will perform in the UpdateTaskActivity.

Open UpdateTaskActivity and write the following code.

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package net.simplifiedcoding.mytodo;

import android.content.DialogInterface;

import android.content.Intent;

import android.os.AsyncTask;

import android.support.v7.app.AlertDialog;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.CheckBox;

import android.widget.EditText;

import android.widget.Toast;

public class UpdateTaskActivity extends AppCompatActivity {

private EditText editTextTask, editTextDesc, editTextFinishBy;

private CheckBox checkBoxFinished;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_update_task);

editTextTask = findViewById(R.id.editTextTask);

editTextDesc = findViewById(R.id.editTextDesc);

editTextFinishBy = findViewById(R.id.editTextFinishBy);

checkBoxFinished = findViewById(R.id.checkBoxFinished);

final Task task = (Task) getIntent().getSerializableExtra("task");

loadTask(task);

findViewById(R.id.button_update).setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

Toast.makeText(getApplicationContext(), "Clicked", Toast.LENGTH_LONG).show();

updateTask(task);

}

});

findViewById(R.id.button_delete).setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

AlertDialog.Builder builder = new AlertDialog.Builder(UpdateTaskActivity.this);

builder.setTitle("Are you sure?");

builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialogInterface, int i) {

deleteTask(task);

}

});

builder.setNegativeButton("No", new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialogInterface, int i) {

}

});

AlertDialog ad = builder.create();

ad.show();

}

});

}

private void loadTask(Task task) {

editTextTask.setText(task.getTask());

editTextDesc.setText(task.getDesc());

editTextFinishBy.setText(task.getFinishBy());

checkBoxFinished.setChecked(task.isFinished());

}

private void updateTask(final Task task) {

final String sTask = editTextTask.getText().toString().trim();

final String sDesc = editTextDesc.getText().toString().trim();

final String sFinishBy = editTextFinishBy.getText().toString().trim();

if (sTask.isEmpty()) {

editTextTask.setError("Task required");

editTextTask.requestFocus();

return;

}

if (sDesc.isEmpty()) {

editTextDesc.setError("Desc required");

editTextDesc.requestFocus();

return;

}

if (sFinishBy.isEmpty()) {

editTextFinishBy.setError("Finish by required");

editTextFinishBy.requestFocus();

return;

}

class UpdateTask extends AsyncTask<Void, Void, Void> {

@Override

protected Void doInBackground(Void... voids) {

task.setTask(sTask);

task.setDesc(sDesc);

task.setFinishBy(sFinishBy);

task.setFinished(checkBoxFinished.isChecked());

DatabaseClient.getInstance(getApplicationContext()).getAppDatabase()

.taskDao()

.update(task);

return null;

}

@Override

protected void onPostExecute(Void aVoid) {

super.onPostExecute(aVoid);

Toast.makeText(getApplicationContext(), "Updated", Toast.LENGTH_LONG).show();

finish();

startActivity(new Intent(UpdateTaskActivity.this, MainActivity.class));

}

UpdateTask ut = new UpdateTask();

ut.execute();

}

private void deleteTask(final Task task) {

class DeleteTask extends AsyncTask<Void, Void, Void> {

@Override

protected Void doInBackground(Void... voids) {

DatabaseClient.getInstance(getApplicationContext()).getAppDatabase()

.taskDao()

.delete(task);

return null;

}

@Override

protected void onPostExecute(Void aVoid) {

super.onPostExecute(aVoid);

Toast.makeText(getApplicationContext(), "Deleted", Toast.LENGTH_LONG).show();

finish();

startActivity(new Intent(UpdateTaskActivity.this, MainActivity.class));

}

DeleteTask dt = new DeleteTask();

dt.execute();

}

In the above code, again we are doing the same thing, we are calling the methods we created inside TaskDao using an AsyncTask.
Now the app is complete you can try running it.

Todo App

So guys we have build the todo application successfully. From below link you can download the apk file.

Download APK