The Firebase database is a NoSQL, real-time, and cloud-hosted database.
Data is stored as JSON and synchronized in real-time to every connected client.
The following steps show how to use the Firebase database:
The Android and Firebase code given in this course is correct, but it may not work for current SDK or API because of the backward compatibility issue.
You should be able to fix it by checking the error messages.
Open Android Studio and create a new project or open an existing project.
†Pick if Java is used.
🡆
🡆
In Android Studio, log in with your email address.
You can find the login button at the top right corner of the Android Studio.
(Remember the email address that you use here.)
If you select the “Test Mode,” your code has to include authentication, which you must update your security rules within 30 days to enable long-term client read/write access.
Now, come back to your Android Studio project.
Connect the Android Studio project to the Firebase project by clicking on 🡆 🡆 🡆 .
After that click on ,
a list of projects will be shown to you.
Select the project that you have created on the Firebase website and click on .
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🡆
Next, you have to add the dependency of Firebase Database in your project by clicking on button and then .
🡇 (after checking )
The build.gradle (Module: My_Firebase.app) file before adding the dependencies is
Add code to the main_activity.xml file.
This application updates and shows the user’s profile consisting of a name and an email address.
So, we will have one TextView for showing the profile and two EditTexts for getting the new values from the user, and an update button.
The code for the main_activity.xml file is given as follows:
The MainActivity.java program saves the name and email address of a user in the Firebase database when starts a new session (emulator).
Afterwards, only the current user’s profile (name and email address) can be updated unless another session starts, and the previous profiles are not able to be updated.
package com.wenchen.myfirebase
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
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 AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName( );
private TextView txtDetails;
private EditText inputName, inputEmail;
private Button btnSave;
private DatabaseReference mFirebaseDatabase;
private FirebaseDatabase mFirebaseInstance;
private String userId;
@Override
protected void onCreate( Bundle savedInstanceState ) {
super.onCreate( savedInstanceState );
setContentView( R.layout.activity_main );
// Displaying toolbar icon
// The action bar does not work, so they are commented out.
androidx.appcompat.app.ActionBar actionBar = getSupportActionBar( );
if ( actionBar != null ) {
// You can safely call methods on the ActionBar now
actionBar.setDisplayHomeAsUpEnabled( true );
actionBar.setIcon( R.mipmap.ic_launcher );
}
else {
// Handle the case where the ActionBar is not available
// (e.g., log an error, use a different UI element, etc.)
Log.e( "MyFirebase", "Action bar is null, cannot set properties");
}
// getSupportActionBar( ).setDisplayShowHomeEnabled( true );
// getSupportActionBar( ).setIcon( R.mipmap.ic_launcher );
txtDetails = (TextView) findViewById( R.id.txt_user );
inputName = (EditText) findViewById( R.id.name );
inputEmail = (EditText) findViewById( R.id.email );
btnSave = (Button) findViewById( R.id.btn_save );
mFirebaseInstance = FirebaseDatabase.getInstance( );
// Getting reference to 'users' node
mFirebaseDatabase = mFirebaseInstance.getReference( "users" );
// Storing app title to 'app_title' node
mFirebaseInstance.getReference( "app_title" ).setValue( "Realtime Database" );
// app_title change listener
mFirebaseInstance.getReference( "app_title" ).addValueEventListener(
new ValueEventListener( ) {
@Override
public void onDataChange( DataSnapshot dataSnapshot ) {
Log.e( TAG, "App title updated" );
String appTitle = dataSnapshot.getValue( String.class );
// Updating toolbar title
// The action bar does not work, so they are commented out.
if ( actionBar != null ) {
// You can safely call methods on the ActionBar now
actionBar.setTitle( appTitle );
}
else {
// Handle the case where the ActionBar is not available
// (e.g., log an error, use a different UI element, etc.)
Log.e( "MyFirebase", "Action bar is null, cannot set properties" );
}
// getSupportActionBar( ).setTitle( appTitle );
}
@Override
public void onCancelled( DatabaseError error ) {
// Failed to read value
Log.e( TAG, "Failed to read app title value.", error.toException( ) );
}
}
);
// Saving or updating the user
btnSave.setOnClickListener(
new View.OnClickListener( ) {
@Override
public void onClick( View view ) {
String name = inputName.getText( ).toString( );
String email = inputEmail.getText( ).toString( );
// Checking for already existed userId
if ( TextUtils.isEmpty( userId ) ) createUser( name, email );
else updateUser( name, email );
}
}
);
toggleButton( );
}
// Changing button text
private void toggleButton( ) {
if ( TextUtils.isEmpty( userId ) ) btnSave.setText( "Save" );
else btnSave.setText( "Update" );
}
//
// Creating new user node under 'users'
//
private void createUser( String name, String email ) {
// TODO
// In real apps this userId should be fetched by using auth
if ( TextUtils.isEmpty( userId ) )
userId = mFirebaseDatabase.push( ).getKey( );
User user = new User( name, email );
mFirebaseDatabase.child( userId ).setValue( user );
addUserChangeListener( );
}
//
// User data change listener
//
private void addUserChangeListener( ) {
mFirebaseDatabase.child( userId ).addValueEventListener(
new ValueEventListener( ) {
@Override
public void onDataChange( DataSnapshot dataSnapshot ) {
User user = dataSnapshot.getValue( User.class );
// Check for null
if ( user == null ) {
Log.e( TAG, "User data is null!" );
return;
}
Log.e( TAG, "User data is changed!" + user.name + ", " + user.email );
// Displaying newly updated name and email
txtDetails.setText( user.name + ", " + user.email );
// Clearing edit text
inputEmail.setText( "" );
inputName.setText ( "" );
toggleButton( );
}
@Override
public void onCancelled( DatabaseError error ) {
// Failed to read value
Log.e( TAG, "Failed to read user", error.toException( ) );
}
}
);
}
private void updateUser( String name, String email ) {
// Updating the user via child nodes
if ( !TextUtils.isEmpty( name ) )
mFirebaseDatabase.child( userId ).child( "name" ).setValue( name );
if ( !TextUtils.isEmpty( email ) )
mFirebaseDatabase.child( userId ).child( "email" ).setValue( email );
}
}
In order to save a user profile, we use a model class called User.java file to store the properties of name and email address (you can add few more properties like address, phone number, etc.):
