FirebaseDatabase

public class FirebaseDatabase

The entry point for accessing a Firebase Database. You can get an instance by calling getInstance. To access a location in the database and read or write data, use getReference.

Summary

Public fields
final FirebaseApp

Public methods
@NonNull FirebaseApp

Returns the FirebaseApp instance to which this FirebaseDatabase belongs.
static @NonNull FirebaseDatabase

Gets the default FirebaseDatabase instance.
static @NonNull FirebaseDatabase

Gets an instance of FirebaseDatabase for a specific FirebaseApp.
static @NonNull FirebaseDatabase

Gets a FirebaseDatabase instance for the specified URL.
synchronized static @NonNull FirebaseDatabase

Gets a FirebaseDatabase instance for the specified URL, using the specified FirebaseApp.
@NonNull DatabaseReference

Gets a DatabaseReference for the database root node.
@NonNull DatabaseReference

Gets a DatabaseReference for the provided path.
@NonNull DatabaseReference

Gets a DatabaseReference for the provided URL.
static @NonNull String
void

Shuts down our connection to the Firebase Database backend until goOnline is called.
void

Resumes our connection to the Firebase Database backend after a previous goOffline call.
void

The Firebase Database client automatically queues writes and sends them to the server at the earliest opportunity, depending on network connectivity.
synchronized void

By default, this is set to INFO.
synchronized void
setPersistenceCacheSizeBytes(long cacheSizeInBytes)

By default Firebase Database will use up to 10MB of disk space to cache data.
synchronized void
setPersistenceEnabled(boolean isEnabled)

The Firebase Database client will cache synchronized data and keep track of all writes you've initiated while your application is running.
void
useEmulator(@NonNull String host, int port)

Modifies this FirebaseDatabase instance to communicate with the Realtime Database emulator.

Public fields

app

public final FirebaseApp app

Public methods

getApp

public @NonNull FirebaseApp getApp()

Returns the FirebaseApp instance to which this FirebaseDatabase belongs.

Returns
@NonNull FirebaseApp

The FirebaseApp instance to which this FirebaseDatabase belongs.

getInstance

public static @NonNull FirebaseDatabase getInstance()

Gets the default FirebaseDatabase instance.

Returns
@NonNull FirebaseDatabase

A FirebaseDatabase instance.

getInstance

public static @NonNull FirebaseDatabase getInstance(@NonNull FirebaseApp app)

Gets an instance of FirebaseDatabase for a specific FirebaseApp.

Parameters
@NonNull FirebaseApp app

The FirebaseApp to get a FirebaseDatabase for.
Returns
@NonNull FirebaseDatabase

A FirebaseDatabase instance.

getInstance

public static @NonNull FirebaseDatabase getInstance(@NonNull String url)

Gets a FirebaseDatabase instance for the specified URL.

Parameters
@NonNull String url

The URL to the Firebase Database instance you want to access.
Returns
@NonNull FirebaseDatabase

A FirebaseDatabase instance.

getInstance

synchronized public static @NonNull FirebaseDatabase getInstance(@NonNull FirebaseApp app, @NonNull String url)

Gets a FirebaseDatabase instance for the specified URL, using the specified FirebaseApp.

Parameters
@NonNull FirebaseApp app

The FirebaseApp to get a FirebaseDatabase for.
@NonNull String url

The URL to the Firebase Database instance you want to access.
Returns
@NonNull FirebaseDatabase

A FirebaseDatabase instance.

getReference

public @NonNull DatabaseReference getReference()

Gets a DatabaseReference for the database root node.

Returns
@NonNull DatabaseReference

A DatabaseReference pointing to the root node.

getReference

public @NonNull DatabaseReference getReference(@NonNull String path)

Gets a DatabaseReference for the provided path.

Parameters
@NonNull String path

Path to a location in your FirebaseDatabase.
Returns
@NonNull DatabaseReference

A DatabaseReference pointing to the specified path.

getReferenceFromUrl

public @NonNull DatabaseReference getReferenceFromUrl(@NonNull String url)

Gets a DatabaseReference for the provided URL. The URL must be a URL to a path within this FirebaseDatabase. To create a DatabaseReference to a different database, create a FirebaseApp with a FirebaseOptions object configured with the appropriate database URL.

Parameters
@NonNull String url

A URL to a path within your database.
Returns
@NonNull DatabaseReference

A DatabaseReference for the provided URL.

getSdkVersion

public static @NonNull String getSdkVersion()
Returns
@NonNull String

The semver version for this build of the Firebase Database client

goOffline

public void goOffline()

Shuts down our connection to the Firebase Database backend until goOnline is called.

goOnline

public void goOnline()

Resumes our connection to the Firebase Database backend after a previous goOffline call.

purgeOutstandingWrites

public void purgeOutstandingWrites()

The Firebase Database client automatically queues writes and sends them to the server at the earliest opportunity, depending on network connectivity. In some cases (e.g. offline usage) there may be a large number of writes waiting to be sent. Calling this method will purge all outstanding writes so they are abandoned.

All writes will be purged, including transactions and onDisconnect writes. The writes will be rolled back locally, perhaps triggering events for affected event listeners, and the client will not (re-)send them to the Firebase backend.

setLogLevel

synchronized public void setLogLevel(@NonNull Logger.Level logLevel)

By default, this is set to INFO. This includes any internal errors (ERROR) and any security debug messages (INFO) that the client receives. Set to DEBUG to turn on the diagnostic logging, and NONE to disable all logging.

Parameters
@NonNull Logger.Level logLevel

The desired minimum log level

setPersistenceCacheSizeBytes

synchronized public void setPersistenceCacheSizeBytes(long cacheSizeInBytes)

By default Firebase Database will use up to 10MB of disk space to cache data. If the cache grows beyond this size, Firebase Database will start removing data that hasn't been recently used. If you find that your application caches too little or too much data, call this method to change the cache size. This method must be called before creating your first Database reference and only needs to be called once per application.

Note that the specified cache size is only an approximation and the size on disk may temporarily exceed it at times. Cache sizes smaller than 1 MB or greater than 100 MB are not supported.

Parameters
long cacheSizeInBytes

The new size of the cache in bytes.

setPersistenceEnabled

synchronized public void setPersistenceEnabled(boolean isEnabled)

The Firebase Database client will cache synchronized data and keep track of all writes you've initiated while your application is running. It seamlessly handles intermittent network connections and re-sends write operations when the network connection is restored.

However by default your write operations and cached data are only stored in-memory and will be lost when your app restarts. By setting this value to `true`, the data will be persisted to on-device (disk) storage and will thus be available again when the app is restarted (even when there is no network connectivity at that time). Note that this method must be called before creating your first Database reference and only needs to be called once per application.

Parameters
boolean isEnabled

Set to true to enable disk persistence, set to false to disable it.

useEmulator

public void useEmulator(@NonNull String host, int port)

Modifies this FirebaseDatabase instance to communicate with the Realtime Database emulator.

Note: Call this method before using the instance to do any database operations.

Parameters
@NonNull String host

the emulator host (for example, 10.0.2.2)
int port

the emulator port (for example, 9000)