Skips data events if they are equal to the previous data event.
The returned stream provides the same events as this stream, except that it never provides two consecutive data events that are equal. That is, errors are passed through to the returned stream, and data events are passed through if they are distinct from the most recently emitted data event.
Equality is determined by the provided equals method. If that is
omitted, the '==' operator on the last provided data element is used.
If equals throws, the data event is replaced by an error event
containing the thrown error. The behavior is equivalent to the
original stream emitting the error event.
The returned stream is a broadcast stream if this stream is.
If a broadcast stream is listened to more than once, each subscription
will individually perform the equals test.
Source
Stream<T> distinct([bool equals(T previous, T next)]) {
return new _DistinctStream<T>(this, equals);
}