addChangeListener abstract method
Adds a listener
to be notified of all changes to Documents in this
database.
Adding a listener
If a Future is returned, the listener will only start listening after the Future has completed. Otherwise the listener is listening immediately after this method returns.
Removing a listener
The returned ListenerToken needs to be provided to removeChangeListener, to remove the given listener. Regardless of whether a Future is returned or not, the listener immediately stops being called.
See also:
- DatabaseChange for the change event given to
listener
. - changes for alternatively listening to changes through a Stream.
- addDocumentChangeListener for listening for changes to a single Document.
- removeChangeListener for removing a previously added listener.
Implementation
FutureOr<ListenerToken> addChangeListener(DatabaseChangeListener listener);