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`	`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.
`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`	`onChildRemoved(@NonNull DataSnapshot snapshot)` 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.