Using Firebase from Android Application

In this blog, I show how to get started with Firebase database and use it from an Android application.

What is Firebase?
Getting started with Firebase
Creating Android Application
Connecting Android Application To Firebase Project
Working with Android Application
Testing

What is Firebase?

Firebase is a realtime database provided by Google. It stores data in JSON format and syncs data between applications running on different devices in realtime using cloud-hosted noSQL database. Data is synced in milliseconds across connected devices.

It is possible to access Firebase data from IOS, Android and JavaScript applications.

So, once you store your data in Firebase, you can update and retrieve data across devices that use IOS, Android and Desktops that run JavaScript.

Getting started with Firebase

In order to use Firebase, you need to log into your google account and take the following steps:

Got to http://console.firebase.google.com
Click on Add Project button and it displays Create a project window.
Enter project name (demo) and then select country - India. Click on Create Project button to create a new project with name demo
On the left panel, select Database option to display database related to the selected project (demo)
At the top select RULES tab and set both read and write permissions to null to enable access to data without any authentication.
```
{
  "rules": {
    ".read": true,
    ".write": true
  }
}
```
Click on Publish to publish new rules.
Dismiss security warning by clicking on DISMISS button.
Click on DATA tab and select root node in your database
Click on + Sign and add a child. When prompted to enter name and value, enter course as name and Android Programming as value.
Click on Add button to save the new child that we created

Now we have a Firebase database with a node called course with value Android Programming. Let us see how to access it from an Android Application.

Creating Android Application

We create a simple Android application to retrieve and update data of course node in Firebase database.

Start Android Studio
Select File -> New -> New Project
In New Project window, enter application name as FireBaseApp and Company domain as srikanthtechnologies.com and select some folder in your system for project location and click on Next. Select other details of your project like API level 16 and Empty Activity and click on Finish button to create a new project.
Select Tools -> Firebase and in Firebase Assistant click on Save and Retrieve data link under Realtime Database
In the next screen, click on Add Realtime Database to your app.
When a window with details regarding which changes are made to build.gradle and app/build.gradle is displayed, Click on Accept Changes to make those changes to gradle scripts. They are needed to let Android application connect to Firebase.
They use google-service.json file to get information about database URL etc. We will obtain google-services.json from Firebase in later steps.

Connecting Android Application To Firebase Project

It is time to connect our application to Firebase database. Here are the steps to connect Android Application to Firebase database.

In Firebase go to home screen and select your project – demo
Select Add Firebase to your Android app button and provide the following details:
- Package name of the Android project - com.srikanthtechnologies.firebaseapp
- Application Nickname - Firebase Android App
Click on REGISTER APP button
Once you click on Register your application in the next step it shows the following window from where you can download google-services.json file by clicking on Download google-services.json button.
When you click on Continue button then it shows what changes you have to make to build.gradle files. As we have already done that using Tools->Firebase in Android Studio, we don't have to do it now. If you missed that step then it is time to make those changes to build.gradle files now.
Now we need to add configuration file to android project.

In Android Studio, change project view from Android to Project so that you see all project related files. Copy google-services.json file in App folder as shown in the following screenshot.

This file contains information that is needed by google services to access Firebase database.

{
  "project_info": {
    "project_number": "271840981827",
    "firebase_url": "https://fir-de130.firebaseio.com",
    "project_id": "fir-de130",
    "storage_bucket": "fir-de130.appspot.com"
  },
  "client": [
    {
      "client_info": {
        "mobilesdk_app_id": "1:271840981827:android:b2beb7634256e5c3",
        "android_client_info": {
          "package_name": "com.srikanthtechnologies.firebaseapp"
        }
      },
      "oauth_client": [
        {
          "client_id": "271840981827-d9p9hfh76k2hcs2jtte83d2h41le5vsd.apps.googleusercontent.com",
          "client_type": 3
        }
      ],
      "api_key": [
        {
          "current_key": "AIzaSyCzLC0rgvAFoHc4a-oGUML9OfDiYOPljjc"
        }
      ],
      "services": {
        "analytics_service": {
          "status": 1
        },
        "appinvite_service": {
          "status": 1,
          "other_platform_oauth_client": []
        },
        "ads_service": {
          "status": 2
        }
      }
    }
  ],
  "configuration_version": "1"
}

Working with Android Application

It is time to create an Activity in Android Application and connect to Firebase database to update and retrieve data from course node.

Add the following components to your Android application:

MainActivity.java

package com.srikanthtechnologies.firebaseapp;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

public class MainActivity extends Activity {

    FirebaseDatabase database = FirebaseDatabase.getInstance();
    DatabaseReference rootRef = database.getReference();
    DatabaseReference courseRef = rootRef.child("course");
    EditText editCourseName;
    TextView textCourseName;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editCourseName = (EditText) findViewById(R.id.editCourseName);
        textCourseName = (TextView) findViewById(R.id.textCourseName);

        // handle value event for course node
        courseRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                    textCourseName.setText(dataSnapshot.getValue().toString());
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    }

    public void updateCourse(View v) {
        // Write a value to course node
        courseRef.setValue(editCourseName.getText().toString());
        Toast.makeText(this,"Updated Course", Toast.LENGTH_LONG).show();
    }

}

Activity_Main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textCourseName"
        android:gravity="center"
        android:textColor="#ff0000"
        android:textAppearance="?android:textAppearanceMedium"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

   <EditText
        android:id="@+id/editCourseName"
        android:hint="Course Name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:onClick="updateCourse"
        android:text="Update"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
            
</LinearLayout>

AndroidManifest.xml

    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.srikanthtechnologies.firebaseapp">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>

</manifest>

Updated Gradle Build Files - app/build.gradle

When we wanted to use Firebase from our application, we added some entries to gradle build files through Tools->Firebase. These entries add required library and google service plugin as shown below:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.3"
    defaultConfig {
        applicationId "com.srikanthtechnologies.firebaseapp"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.3.1'
    compile 'com.google.firebase:firebase-database:10.0.1'
    testCompile 'junit:junit:4.12'
}


apply plugin: 'com.google.gms.google-services'

Testing

It is time to test Android application to see whether we can retrieve and update Firebase data.

Build Android Application using Build -> Build APK.

Run Android Application either in Emulator or Device. In the beginning, MainActivity must show current value of course node from Firebase database as shown in the following screen:

Enter new course name (Angular 2 Programming) in EditText and click on Update button to change value in Firebase database.

As Firebase database changes, it notifies our application about change by calling onDateChange method. We update our TextView with new value. Remember, no matter how the value of course is changed in Firebase, our application is notified with onDataChange event to enable our application to take a Snapshot of data.

Here are some links that provide you relevant details:

Add Firebase to your Android Project
Firebase Documentation