ChildEventListener
public interfaceChildEventListener
Classes implementing this interface can be used to receive events about changes in the child locations of a givenDatabaseReference ref. Attach the listener to a location usingaddChildEventListener and the appropriate method will be triggered when changes occur.
Summary
Public methods | |
|---|---|
abstract void | onCancelled(@NonNullDatabaseError 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(This method is triggered when a new child is added to the location to which this listener was added. |
abstract void | onChildChanged(This method is triggered when the data at a child location has changed. |
abstract void | onChildMoved(This method is triggered when a child location's priority changes. |
abstract void | onChildRemoved(@NonNullDataSnapshot 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(@NonNullDatabaseError 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 | |
|---|---|
@NonNullDatabaseError error | A description of the error that occurred |
onChildAdded
abstract void onChildAdded(
@NonNullDataSnapshot snapshot,
@NullableString previousChildName
)
This method is triggered when a new child is added to the location to which this listener was added.
| Parameters | |
|---|---|
@NonNullDataSnapshot snapshot | An immutable snapshot of the data at the new child location |
@NullableString 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(
@NonNullDataSnapshot snapshot,
@NullableString previousChildName
)
This method is triggered when the data at a child location has changed.
| Parameters | |
|---|---|
@NonNullDataSnapshot snapshot | An immutable snapshot of the data at the new data at the child location |
@NullableString 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(
@NonNullDataSnapshot snapshot,
@NullableString previousChildName
)
This method is triggered when a child location's priority changes. SeesetPriority andOrdered Data for more information on priorities and ordering data.
| Parameters | |
|---|---|
@NonNullDataSnapshot snapshot | An immutable snapshot of the data at the location that moved. |
@NullableString 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(@NonNullDataSnapshot snapshot)
This method is triggered when a child is removed from the location to which this listener was added.
| Parameters | |
|---|---|
@NonNullDataSnapshot snapshot | An immutable snapshot of the data at the child that was removed. |
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Last updated 2025-07-21 UTC.