If you haven't already,
add Firebase to your Android project
.
Create a Database
Navigate to the
Realtime Database
section of the
Firebase console
.
You'll be prompted to select an existing Firebase project.
Follow the database creation workflow.
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, Apple, or Android SDK, select testmode.
- Locked mode
Denies all reads and writes from mobile and web clients.
Your authenticated application servers can still access your database.
Choose a location for the database.
Depending on the
location of the database
, the
URL for the new database will be in one of the following forms:
Click
Done
.
When you enable Realtime Database, it also enables the API in the
Cloud API Manager
.
Add the Realtime Database SDK to your app
In your
module (app-level) Gradle file
(usually
<project>/<app-module>/build.gradle.kts
or
<project>/<app-module>/build.gradle
),
add the dependency for the Realtime Database library for Android. We recommend using the
Firebase Android BoM
to control library versioning.
dependencies {
// Import the BoM for the Firebase platform
implementation(platform("com.google.firebase:firebase-bom:32.8.1"))
// Add the dependency for the Realtime Database library
// When using the BoM, you don't specify versions in Firebase library dependencies
implementation("com.google.firebase:firebase-database")
}
By using the
Firebase Android BoM
,
your app will always use compatible versions of Firebase Android libraries.
(Alternative)
Add Firebase library dependencies
without
using the BoM
If you choose not to use the Firebase BoM, you must specify each Firebase library version
in its dependency line.
Note that if you use
multiple
Firebase libraries in your app, we strongly
recommend using the BoM to manage library versions, which ensures that all versions are
compatible.
dependencies {
// Add the dependency for the Realtime Database library
// When NOT using the BoM, you must specify versions in Firebase library dependencies
implementation("com.google.firebase:firebase-database:20.3.1")
}
Looking for a Kotlin-specific library module?
Starting in
October 2023
(Firebase BoM 32.5.0)
, both Kotlin and Java developers can
depend on the main library module (for details, see the
FAQ about this initiative
).
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.
Write to your database
Retrieve an instance of your database using
getInstance()
and
reference the location you want to write to.
Kotlin+KTX
// Write a message to the database
val database = Firebase.database
val myRef = database.getReference("message")
myRef.setValue("Hello, World!")
Java
// Write a message to the database
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("message");
myRef.setValue("Hello, World!");
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.
Kotlin+KTX
// 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>()
Log.d(TAG, "Value is: $value")
}
override fun onCancelled(error: DatabaseError) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException())
}
})
Java
// Read from the database
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull 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(@NonNull DatabaseError error) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException());
}
});
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 this rule to fit the structure of your app.
-keepclassmembers class com.yourcompany.models.** {
*;
}
To get help for questions or issues related to ProGuard, visit the
Guardsquare Community forums
to get assistance from an expert.
Prepare for Launch
Before launching your app, we recommend walking through our
launch checklist
to make sure your app is
ready to go!
Be sure to enable
App Check
to help ensure that
only your apps can access your databases.
Next Steps