Installation & Setup on Android

Connect your App to Firebase

If you haven't already, add Firebase to your Android project.

In your project-level build.gradle file, make sure to include Google's Maven repository in both your buildscript and allprojects sections.

Create a Database

  1. If you haven't already, create a Firebase project: In the Firebase console, click Add project, then follow the on-screen instructions to create a Firebase project or to add Firebase services to an existing GCP project.

  2. Navigate to the Database section of the Firebase console. You'll be prompted to select an existing Firebase project. Follow the database creation workflow.

  3. Select a starting mode for your Firebase Security Rules:

    Test mode

    Good for getting started with the mobile and web client libraries, but allows anyone to read and overwrite your data. After testing, make sure to review the Understand Firebase Realtime Database Rules section.

    To get started with the web, iOS, or Android SDK, select test mode.

    Locked mode

    Denies all reads and writes from mobile and web clients. Your authenticated application servers can still access your database.

  4. Click Done.

When you enable Realtime Database, it also enables the API in the Cloud API Manager.

Add the Realtime Database to your app

Add the dependency for Realtime Database to your app-level build.gradle file:

  implementation 'com.google.firebase:firebase-database:19.2.1'

Configure Realtime Database Rules

The Realtime Database provides a declarative rules language that allows you to define how your data should be structured, how it should be indexed, and when your data can be read from and written to.

By default, read and write access to your database is restricted so only authenticated users can read or write data. To get started without setting up Authentication, you can configure your rules for public access. This does make your database open to anyone, even people not using your app, so be sure to restrict your database again when you set up authentication.

Write to your database

Retrieve an instance of your database using getInstance() and reference the location you want to write to.

Java 

// Write a message to the database
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("message");

myRef.setValue("Hello, World!");
MainActivity.java

Kotlin 

// Write a message to the database
val database = FirebaseDatabase.getInstance()
val myRef = database.getReference("message")

myRef.setValue("Hello, World!")
MainActivity.kt

You can save a range of data types to the database this way, including Java objects. When you save an object the responses from any getters will be saved as children of this location.

Read from your database

To make your app data update in realtime, you should add a ValueEventListener to the reference you just created.

The onDataChange() method in this class is triggered once when the listener is attached and again every time the data changes, including the children.

Java 

// Read from the database
myRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        // This method is called once with the initial value and again
        // whenever data at this location is updated.
        String value = dataSnapshot.getValue(String.class);
        Log.d(TAG, "Value is: " + value);
    }

    @Override
    public void onCancelled(DatabaseError error) {
        // Failed to read value
        Log.w(TAG, "Failed to read value.", error.toException());
    }
});
MainActivity.java

Kotlin 

// Read from the database
myRef.addValueEventListener(object : ValueEventListener {
    override fun onDataChange(dataSnapshot: DataSnapshot) {
        // This method is called once with the initial value and again
        // whenever data at this location is updated.
        val value = dataSnapshot.getValue(String::class.java)
        Log.d(TAG, "Value is: $value")
    }

    override fun onCancelled(error: DatabaseError) {
        // Failed to read value
        Log.w(TAG, "Failed to read value.", error.toException())
    }
})
MainActivity.kt

Optional: Configure ProGuard

When using Firebase Realtime Database in your app along with ProGuard, you need to consider how your model objects will be serialized and deserialized after obfuscation. If you use <DataSnapshot.getValue(Class) or DatabaseReference.setValue(Object) to read and write data, you will need to add rules to the proguard-rules.pro file:

    # Add this global rule
    -keepattributes Signature

    # This rule will properly ProGuard all the model classes in
    # the package com.yourcompany.models. Modify to fit the structure
    # of your app.
    -keepclassmembers class com.yourcompany.models.** {
      *;
    }

Prepare for Launch

Before launching your app, we recommend walking through our launch checklist to make sure your app is ready to go!

Next Steps