DatabaseReference

A Firebase reference represents a particular location in your Database and can be used for reading or writing data to that Database location.

This class is the starting point for all Database operations. After you've initialized it with a URL, you can use it to read data, write data, and to create new DatabaseReferences.

Nested Class Summary

interface DatabaseReference.CompletionListener This interface is used as a method of being notified when an operation has been acknowledged by the Database servers and can be considered complete

Public Method Summary

DatabaseReference	child(String pathString) Get a reference to location relative to this one
boolean	equals(Object other)
FirebaseDatabase	getDatabase() Gets the Database instance associated with this reference.
String	getKey()
DatabaseReference	getParent()
DatabaseReference	getRoot()
static void	goOffline() Manually disconnect the Firebase Database client from the server and disable automatic reconnection.
static void	goOnline() Manually reestablish a connection to the Firebase Database server and enable automatic reconnection.
int	hashCode()
OnDisconnect	onDisconnect() Provides access to disconnect operations at this location
DatabaseReference	push() Create a reference to an auto-generated child location.
Task<Void>	removeValue() Set the value at this location to 'null'
void	removeValue(DatabaseReference.CompletionListener listener) Set the value at this location to 'null'
void	runTransaction(Transaction.Handler handler, boolean fireLocalEvents) Run a transaction on the data at this location.
void	runTransaction(Transaction.Handler handler) Run a transaction on the data at this location.
void	setPriority(Object priority, DatabaseReference.CompletionListener listener) Set a priority for the data at this Database location.
Task<Void>	setPriority(Object priority) Set a priority for the data at this Database location.
void	setValue(Object value, Object priority, DatabaseReference.CompletionListener listener) Set the data and priority to the given values.
void	setValue(Object value, DatabaseReference.CompletionListener listener) Set the data at this location to the given value.
Task<Void>	setValue(Object value, Object priority) Set the data and priority to the given values.
Task<Void>	setValue(Object value) Set the data at this location to the given value.
String	toString()
Task<Void>	updateChildren(Map<String, Object> update) Update the specific child keys to the specified values.
void	updateChildren(Map<String, Object> update, DatabaseReference.CompletionListener listener) Update the specific child keys to the specified values.

Inherited Method Summary

From class com.google.firebase.database.Query

ChildEventListener	addChildEventListener(ChildEventListener listener) Add a listener for child events occurring at this location.
void	addListenerForSingleValueEvent(ValueEventListener listener) Add a listener for a single change in the data at this location.
ValueEventListener	addValueEventListener(ValueEventListener listener) Add a listener for changes in the data at this location.
Query	endAt(String value, String key) Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key key less than or equal to the given key.
Query	endAt(String value) Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
Query	endAt(double value, String key) Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key less than or equal to the given key.
Query	endAt(double value) Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
Query	endAt(boolean value) Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
Query	endAt(boolean value, String key) Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key less than or equal to the given key.
Query	equalTo(String value, String key) Create a query constrained to only return the child node with the given key and value.
Query	equalTo(double value) Create a query constrained to only return child nodes with the given value
Query	equalTo(double value, String key) Create a query constrained to only return the child node with the given key and value.
Query	equalTo(String value) Create a query constrained to only return child nodes with the given value
Query	equalTo(boolean value, String key) Create a query constrained to only return the child node with the given key and value.
Query	equalTo(boolean value) Create a query constrained to only return child nodes with the given value.
DatabaseReference	getRef()
void	keepSynced(boolean keepSynced) By calling `keepSynced(true)` on a location, the data for that location will automatically be downloaded and kept in sync, even when no listeners are attached for that location.
Query	limitToFirst(int limit) Create a query with limit and anchor it to the start of the window
Query	limitToLast(int limit) Create a query with limit and anchor it to the end of the window
Query	orderByChild(String path) Create a query in which child nodes are ordered by the values of the specified path.
Query	orderByKey() Create a query in which child nodes are ordered by their keys.
Query	orderByPriority() Create a query in which child nodes are ordered by their priorities.
Query	orderByValue() Create a query in which nodes are ordered by their value
void	removeEventListener(ChildEventListener listener) Remove the specified listener from this location.
void	removeEventListener(ValueEventListener listener) Remove the specified listener from this location.
Query	startAt(double value) Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
Query	startAt(String value, String key) Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
Query	startAt(String value) Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
Query	startAt(double value, String key) Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
Query	startAt(boolean value) Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
Query	startAt(boolean value, String key) Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.

From class java.lang.Object

Object	clone()
boolean	equals(Object arg0)
void	finalize()
final Class<?>	getClass()
int	hashCode()
final void	notify()
final void	notifyAll()
String	toString()
final void	wait(long arg0, int arg1)
final void	wait(long arg0)
final void	wait()

Public Methods

public DatabaseReference child (String pathString)

Also: Google Play services

Get a reference to location relative to this one

Parameters

pathString	The relative path from this reference to the new one that should be created

Returns

A new DatabaseReference to the given path

public boolean equals (Object other)

Parameters

other

public FirebaseDatabase getDatabase ()

Also: Google Play services

Gets the Database instance associated with this reference.

Returns

The Database object for this reference.

public String getKey ()

Also: Google Play services

Returns

The last token in the location pointed to by this reference or null if this reference points to the database root

public DatabaseReference getParent ()

Also: Google Play services

Returns

A DatabaseReference to the parent location, or null if this instance references the root location

public DatabaseReference getRoot ()

Also: Google Play services

Returns

A reference to the root location of this Firebase Database

public static void goOffline ()

Also: Google Play services

Manually disconnect the Firebase Database client from the server and disable automatic reconnection.

Note: Invoking this method will impact all Firebase Database connections.

public static void goOnline ()

Also: Google Play services

Manually reestablish a connection to the Firebase Database server and enable automatic reconnection.

Note: Invoking this method will impact all Firebase Database connections.

public int hashCode ()

public OnDisconnect onDisconnect ()

Also: Google Play services

Provides access to disconnect operations at this location

Returns

An object for managing disconnect operations at this location

public DatabaseReference push ()

Also: Google Play services

Create a reference to an auto-generated child location. The child key is generated client-side and incorporates an estimate of the server's time for sorting purposes. Locations generated on a single client will be sorted in the order that they are created, and will be sorted approximately in order across all clients.

Returns

A DatabaseReference pointing to the new location

public Task<Void> removeValue ()

Also: Google Play services

Set the value at this location to 'null'

Returns

The Task for this operation.

public void removeValue (DatabaseReference.CompletionListener listener)

Also: Google Play services

Set the value at this location to 'null'

Parameters

listener	A listener that will be triggered when the operation is complete

public void runTransaction (Transaction.Handler handler, boolean fireLocalEvents)

Also: Google Play services

Run a transaction on the data at this location. For more information on running transactions, see Transaction.Handler.

Parameters

handler	An object to handle running the transaction
fireLocalEvents	Defaults to true. If set to false, events will only be fired for the final result state of the transaction, and not for any intermediate states

public void runTransaction (Transaction.Handler handler)

Also: Google Play services

Run a transaction on the data at this location. For more information on running transactions, see Transaction.Handler.

Parameters

handler	An object to handle running the transaction

public void setPriority (Object priority, DatabaseReference.CompletionListener listener)

Also: Google Play services

Set a priority for the data at this Database location. Priorities can be used to provide a custom ordering for the children at a location (if no priorities are specified, the children are ordered by key).

You cannot set a priority on an empty location. For this reason setValue(data, priority) should be used when setting initial data with a specific priority and setPriority should be used when updating the priority of existing data.

Children are sorted based on this priority using the following rules:

Children with no priority come first.
Children with a number as their priority come next. They are sorted numerically by priority (small to large).
Children with a string as their priority come last. They are sorted lexicographically by priority.
Whenever two children have the same priority (including no priority), they are sorted by key. Numeric keys come first (sorted numerically), followed by the remaining keys (sorted lexicographically).

Note that numerical priorities are parsed and ordered as IEEE 754 double-precision floating-point numbers. Keys are always stored as strings and are treated as numeric only when they can be parsed as a 32-bit integer.

Parameters

priority	The priority to set at the specified location or null to clear the existing priority
listener	A listener that will be triggered with results of the operation

public Task<Void> setPriority (Object priority)

Also: Google Play services

Children with no priority come first.
Children with a number as their priority come next. They are sorted numerically by priority (small to large).
Children with a string as their priority come last. They are sorted lexicographically by priority.
Whenever two children have the same priority (including no priority), they are sorted by key. Numeric keys come first (sorted numerically), followed by the remaining keys (sorted lexicographically).

Parameters

priority	The priority to set at the specified location or null to clear the existing priority

Returns

The Task for this operation.

public void setValue (Object value, Object priority, DatabaseReference.CompletionListener listener)

Also: Google Play services

Set the data and priority to the given values. The native types accepted by this method for the value correspond to the JSON types:

Boolean
Long
Double
String
Map<String, Object>
List<Object>

In addition, you can set instances of your own class into this location, provided they satisfy the following constraints:

The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Generic collections of objects that satisfy the above constraints are also permitted, i.e. Map<String, MyPOJO>, as well as null values.

Parameters

value	The value to set at this location or null to delete the existing data
priority	The priority to set at this location or null to clear the existing priority
listener	A listener that will be triggered with the results of the operation

public void setValue (Object value, DatabaseReference.CompletionListener listener)

Also: Google Play services

Set the data at this location to the given value. Passing null to setValue() will delete the data at the specified location. The native types accepted by this method for the value correspond to the JSON types:

Boolean
Long
Double
String
Map<String, Object>
List<Object>

In addition, you can set instances of your own class into this location, provided they satisfy the following constraints:

The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Generic collections of objects that satisfy the above constraints are also permitted, i.e. Map<String, MyPOJO>, as well as null values.

Parameters

value	The value to set at this location or null to delete the existing data
listener	A listener that will be triggered with the results of the operation

public Task<Void> setValue (Object value, Object priority)

Also: Google Play services

Set the data and priority to the given values. Passing null to setValue() will delete the data at the specified location. The native types accepted by this method for the value correspond to the JSON types:

Boolean
Long
Double
String
Map<String, Object>
List<Object>

In addition, you can set instances of your own class into this location, provided they satisfy the following constraints:

The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Generic collections of objects that satisfy the above constraints are also permitted, i.e. Map<String, MyPOJO>, as well as null values.

Parameters

value	The value to set at this location or null to delete the existing data
priority	The priority to set at this location or null to clear the existing priority

Returns

The Task for this operation.

public Task<Void> setValue (Object value)

Also: Google Play services

Boolean
Long
Double
String
Map<String, Object>
List<Object>

In addition, you can set instances of your own class into this location, provided they satisfy the following constraints:

The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Generic collections of objects that satisfy the above constraints are also permitted, i.e. Map<String, MyPOJO>, as well as null values.

Parameters

value	The value to set at this location or null to delete the existing data

Returns

The Task for this operation.

public String toString ()

Returns

The full location url for this reference

public Task<Void> updateChildren (Map<String, Object> update)

Also: Google Play services

Update the specific child keys to the specified values. Passing null in a map to updateChildren() will remove the value at the specified location.

Parameters

update	The paths to update and their new values

Returns

The Task for this operation.

public void updateChildren (Map<String, Object> update, DatabaseReference.CompletionListener listener)

Also: Google Play services

Update the specific child keys to the specified values. Passing null in a map to updateChildren() will remove the value at the specified location.

Parameters

update	The paths to update and their new values
listener	A listener that will be triggered with results of the operation