The callback which is called when the stream is listened to.
May be set to null
, in which case no callback will happen.
ControllerCallback get onListen;void onListen= (
void set onListen(void onListenHandler());
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Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-async/StreamController/onListen.html