add
Adds an OnUndoHistoryChangeListener for being notified of changes to the undo manager's edit history (i.e. its undo and redo stacks). If a listener has already been added previously, this method will be a no-op. Passing null is not allowed and will result in an exception.
Parameters
listener
OnUndoHistoryChangeListener that should be notified. Must be non-null.
See also
.removeOnUndoHistoryChangeListener