Forwards data events while test is successful.
The returned stream provides the same events as this stream as long
as test returns true for the event data. The stream is done
when either this stream is done, or when this stream first provides
a value that test doesn't accept.
Stops listening to the stream after the accepted elements.
Internally the method cancels its subscription after these elements. This means that single-subscription (non-broadcast) streams are closed and cannot be reused after a call to this method.
The returned stream is a broadcast stream if this stream is. For a broadcast stream, the events are only tested from the time the returned stream is listened to.
Source
Stream<T> takeWhile(bool test(T element)) {
return new _TakeWhileStream<T>(this, test);
}