Adds a subscription to this stream.
Returns a StreamSubscription which handles events from the stream using the provided onData
, onError
and onDone
handlers. The handlers can be changed on the subscription, but they start out as the provided functions.
On each data event from this stream, the subscriber's onData
handler is called. If onData
is null
, nothing happens.
On errors from this stream, the onError
handler is called with the error object and possibly a stack trace.
The onError
callback must be of type void onError(error)
or void onError(error, StackTrace stackTrace)
. If onError
accepts two arguments it is called with the error object and the stack trace (which could be null
if the stream itself received an error without stack trace). Otherwise it is called with just the error object. If onError
is omitted, any errors on the stream are considered unhandled, and will be passed to the current Zone's error handler. By default unhandled async errors are treated as if they were uncaught top-level errors.
If this stream closes and sends a done event, the onDone
handler is called. If onDone
is null
, nothing happens.
If cancelOnError
is true, the subscription is automatically canceled when the first error event is delivered. The default is false
.
While a subscription is paused, or when it has been canceled, the subscription doesn't receive events and none of the event handler functions are called.
StreamSubscription<T> listen(void onData(T event), {Function onError, void onDone(), bool cancelOnError});
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-async/Stream/listen.html