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(ChildEventListener)
and the
appropriate method will be triggered when changes occur.
Public Method Summary
abstract void |
onCancelled(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(DataSnapshot snapshot, String previousChildName)
This method is triggered when a new child is added to the location to which this listener was
added.
|
abstract void |
onChildChanged(DataSnapshot snapshot, String previousChildName)
This method is triggered when the data at a child location has changed.
|
abstract void |
onChildMoved(DataSnapshot snapshot, String previousChildName)
This method is triggered when a child location's priority changes.
|
abstract void |
onChildRemoved(DataSnapshot snapshot)
This method is triggered when a child is removed from the location to which this listener was
added.
|
Public Methods
public abstract void onCancelled (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
error | A description of the error that occurred |
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public abstract void onChildAdded (DataSnapshot snapshot, String previousChildName)
This method is triggered when a new child is added to the location to which this listener was added.
Parameters
snapshot | An immutable snapshot of the data at the new child location |
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previousChildName | The key name of sibling location ordered before the new child. This will be null for the first child node of a location. |
public abstract void onChildChanged (DataSnapshot snapshot, String previousChildName)
This method is triggered when the data at a child location has changed.
Parameters
snapshot | An immutable snapshot of the data at the new data at the child location |
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previousChildName | The key name of sibling location ordered before the child. This will be null for the first child node of a location. |
public abstract void onChildMoved (DataSnapshot snapshot, String previousChildName)
This method is triggered when a child location's priority changes. See setPriorityAsync(Object)
and Ordered Data for more information on priorities and ordering data.
Parameters
snapshot | An immutable snapshot of the data at the location that moved. |
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previousChildName | The key name of the sibling location ordered before the child location. This will be null if this location is ordered first. |
public abstract void onChildRemoved (DataSnapshot snapshot)
This method is triggered when a child is removed from the location to which this listener was added.
Parameters
snapshot | An immutable snapshot of the data at the child that was removed. |
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