ChildEventListener

public interface ChildEventListener


Classes implementing this interface can be used to receive events about changes in the child locations of a given DatabaseReference ref. Attach the listener to a location using addChildEventListener and the appropriate method will be triggered when changes occur.

Summary

Public methods

abstract void

This method will be triggered in the event that this listener either failed at the server, or is removed as a result of the security and Firebase rules.

abstract void
onChildAdded(
    @NonNull DataSnapshot snapshot,
    @Nullable String previousChildName
)

This method is triggered when a new child is added to the location to which this listener was added.

abstract void
onChildChanged(
    @NonNull DataSnapshot snapshot,
    @Nullable String previousChildName
)

This method is triggered when the data at a child location has changed.

abstract void
onChildMoved(
    @NonNull DataSnapshot snapshot,
    @Nullable String previousChildName
)

This method is triggered when a child location's priority changes.

abstract void

This method is triggered when a child is removed from the location to which this listener was added.

Public methods

onCancelled

abstract void onCancelled(@NonNull DatabaseError error)

This method will be triggered in the event that this listener either failed at the server, or is removed as a result of the security and Firebase rules. For more information on securing your data, see: Security Quickstart

Parameters
@NonNull DatabaseError error

A description of the error that occurred

onChildAdded

abstract void onChildAdded(
    @NonNull DataSnapshot snapshot,
    @Nullable String previousChildName
)

This method is triggered when a new child is added to the location to which this listener was added.

Parameters
@NonNull DataSnapshot snapshot

An immutable snapshot of the data at the new child location

@Nullable String previousChildName

The key name of sibling location ordered before the new child. This will be null for the first child node of a location.

onChildChanged

abstract void onChildChanged(
    @NonNull DataSnapshot snapshot,
    @Nullable String previousChildName
)

This method is triggered when the data at a child location has changed.

Parameters
@NonNull DataSnapshot snapshot

An immutable snapshot of the data at the new data at the child location

@Nullable String previousChildName

The key name of sibling location ordered before the child. This will be null for the first child node of a location.

onChildMoved

abstract void onChildMoved(
    @NonNull DataSnapshot snapshot,
    @Nullable String previousChildName
)

This method is triggered when a child location's priority changes. See setPriority and Ordered Data for more information on priorities and ordering data.

Parameters
@NonNull DataSnapshot snapshot

An immutable snapshot of the data at the location that moved.

@Nullable String previousChildName

The key name of the sibling location ordered before the child location. This will be null if this location is ordered first.

onChildRemoved

abstract void onChildRemoved(@NonNull DataSnapshot snapshot)

This method is triggered when a child is removed from the location to which this listener was added.

Parameters
@NonNull DataSnapshot snapshot

An immutable snapshot of the data at the child that was removed.