DataSnapshot

public class DataSnapshot

A DataSnapshot instance contains data from a Firebase Database location. Any time you read Database data, you receive the data as a DataSnapshot. DataSnapshots are passed to the methods in listeners that you attach with addValueEventListener, addChildEventListener, or addListenerForSingleValueEvent. They are efficiently-generated immutable copies of the data at a Firebase Database location. They can't be modified and will never change. To modify data at a location, use a DatabaseReference reference (e.g. with setValue).

Summary

Public methods
`@NonNull DataSnapshot`	`child(@NonNull String path)` Get a DataSnapshot for the location at the specified relative path.
`boolean`	`exists()` Returns true if the snapshot contains a non-null value.
`@NonNull Iterable<DataSnapshot>`	`getChildren()` Gives access to all of the immediate children of this snapshot.
`long`	`getChildrenCount()`
`@Nullable String`	`getKey()`
`@Nullable Object`	`getPriority()` Returns the priority of the data contained in this snapshot as a native type.
`@NonNull DatabaseReference`	`getRef()` Used to obtain a reference to the source location for this snapshot.
`@Nullable Object`	`getValue()` getValue() returns the data contained in this snapshot as native types.
`@Nullable T`	`<T> getValue(@NonNull GenericTypeIndicator<T> t)` Due to the way that Java implements generics, it takes an extra step to get back a properly-typed Collection.
`@Nullable Object`	`getValue(boolean useExportFormat)` getValue() returns the data contained in this snapshot as native types.
`@Nullable T`	`<T> getValue(@NonNull Class<T> valueType)` This method is used to marshall the data contained in this snapshot into a class of your choosing.
`boolean`	`hasChild(@NonNull String path)` Can be used to determine if this DataSnapshot has data at a particular location
`boolean`	`hasChildren()` Indicates whether this snapshot has any children
`String`	`toString()`

Extension functions
`final T`	`<T extends Object> DatabaseKt.getValue(@NonNull DataSnapshot receiver)` Returns the content of the DataSnapshot converted to a POJO.
`final T`	`<T extends Object> DatabaseKt.getValue(@NonNull DataSnapshot receiver)` This method is deprecated. Migrate to use the KTX API from the main module: https://firebase.google.com/docs/android/kotlin-migration.

Public methods

child

public @NonNull DataSnapshot child(@NonNull String path)

Get a DataSnapshot for the location at the specified relative path. The relative path can either be a simple child key (e.g. 'fred') or a deeper slash-separated path (e.g. 'fred/name/first'). If the child location has no data, an empty DataSnapshot is returned.

Parameters
`@NonNull String path`	A relative path to the location of child data

Returns
`@NonNull DataSnapshot`	The DataSnapshot for the child location

exists

public boolean exists()

Returns true if the snapshot contains a non-null value.

Returns
`boolean`	True if the snapshot contains a non-null value, otherwise false

getChildren

public @NonNull Iterable<DataSnapshot> getChildren()

Gives access to all of the immediate children of this snapshot. Can be used in native for loops:

for (DataSnapshot child : parent.getChildren()) {
      ...
}

Returns
`@NonNull Iterable<DataSnapshot>`	The immediate children of this snapshot

getChildrenCount

public long getChildrenCount()

Returns
`long`	The number of immediate children in the this snapshot

getKey

public @Nullable String getKey()

Returns
`@Nullable String`	The key name for the source location of this snapshot or null if this snapshot points to the database root.

getPriority

public @Nullable Object getPriority()

Returns the priority of the data contained in this snapshot as a native type. Possible return types:

Double
String

Note that null is also allowed

Returns
`@Nullable Object`	the priority of the data contained in this snapshot as a native type

getRef

public @NonNull DatabaseReference getRef()

Used to obtain a reference to the source location for this snapshot.

Returns
`@NonNull DatabaseReference`	A DatabaseReference corresponding to the location that this snapshot came from

getValue

public @Nullable Object getValue()

getValue() returns the data contained in this snapshot as native types. The possible types returned are:

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

This list is recursive; the possible types for java.lang.Object in the above list is given by the same list. These types correspond to the types available in JSON.

Returns
`@Nullable Object`	The data contained in this snapshot as native types or null if there is no data at this location.

getValue

public @Nullable T <T> getValue(@NonNull GenericTypeIndicator<T> t)

Due to the way that Java implements generics, it takes an extra step to get back a properly-typed Collection. So, in the case where you want a java.util.List of Message instances, you will need to do something like the following:

    GenericTypeIndicator<List<Message>> t = new GenericTypeIndicator<List<Message>>() {};
    List<Message> messages = snapshot.getValue(t);

It is important to use a subclass of GenericTypeIndicator. See GenericTypeIndicator for more details

Parameters
`<T>`	The type to return. Implicitly defined from the `GenericTypeIndicator` passed in
`@NonNull GenericTypeIndicator<T> t`	A subclass of `GenericTypeIndicator` indicating the type of generic collection to be returned.

Returns
`@Nullable T`	A properly typed collection, populated with the data from this snapshot, or null if there is no data at this location.

getValue

public @Nullable Object getValue(boolean useExportFormat)

getValue() returns the data contained in this snapshot as native types. The possible types returned are:

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

This list is recursive; the possible types for java.lang.Object in the above list is given by the same list. These types correspond to the types available in JSON.

If useExportFormat is set to true, priority information will be included in the output. Priority information shows up as a .priority key in a map. For data that would not otherwise be a map, the map will also include a .value key with the data.

Parameters
`boolean useExportFormat`	Whether or not to include priority information

Returns
`@Nullable Object`	The data in native types, along with its priority, or null if there is no data at this location.

getValue

public @Nullable T <T> getValue(@NonNull Class<T> valueType)

This method is used to marshall the data contained in this snapshot into a class of your choosing. The class must fit 2 simple 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

An example class might look like:

    class Message {
        private String author;
        private String text;

        private Message() {}

        public Message(String author, String text) {
            this.author = author;
            this.text = text;
        }

        public String getAuthor() {
            return author;
        }

        public String getText() {
            return text;
        }
    }


    // Later
    Message m = snapshot.getValue(Message.class);

Parameters
`<T>`	The type to return. Implicitly defined from the class passed in
`@NonNull Class<T> valueType`	The class into which this snapshot should be marshalled

Returns
`@Nullable T`	An instance of the class passed in, populated with the data from this snapshot, or null if there is no data at this location.

hasChild

public boolean hasChild(@NonNull String path)

Can be used to determine if this DataSnapshot has data at a particular location

Parameters
`@NonNull String path`	A relative path to the location of child data

Returns
`boolean`	Whether or not the specified child location has data

hasChildren

public boolean hasChildren()

Indicates whether this snapshot has any children

Returns
`boolean`	True if the snapshot has any children, otherwise false

toString

public String toString()

Extension functions

DatabaseKt.getValue

public final T <T extends Object> DatabaseKt.getValue(@NonNull DataSnapshot receiver)

Returns the content of the DataSnapshot converted to a POJO.

Supports generics like List<> or Map<>. Use @JvmSuppressWildcards to force the compiler to use the type T, and not ? extends T.

DatabaseKt.getValue

public final T <T extends Object> DatabaseKt.getValue(@NonNull DataSnapshot receiver)

Returns the content of the DataSnapshot converted to a POJO.

Supports generics like List<> or Map<>. Use @JvmSuppressWildcards to force the compiler to use the type T, and not ? extends T.

Deprecation Notice: The Kotlin extensions (KTX) APIs have been added to their respective main modules, and the Kotlin extension (KTX) APIs in com.google.firebase.firebase-database-ktx are now deprecated. As early as April 2024, we'll no longer release KTX modules. For details, see the FAQ about this initiative.