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Stream用于接收异步事件Stream 可以接收多个异步事件Stream.listen()方法返回StreamSubscription 可用于取消事件订阅#xff0c;取消后#xff0c;不再接收事件
基本使用 Stream.fromFutures([Future.delayed(Duration(seconds: 1),(){return 事件1;})…Stream
Stream用于接收异步事件Stream 可以接收多个异步事件Stream.listen()方法返回StreamSubscription 可用于取消事件订阅取消后不再接收事件
基本使用 Stream.fromFutures([Future.delayed(Duration(seconds: 1),(){return 事件1;}),Future.delayed(Duration(seconds: 3),(){return 事件2;}),Future.delayed(Duration(seconds: 5),(){return 事件3;})]).listen((event) {print(${DateTime.now().millisecondsSinceEpoch} event);}).onDone(() {print(${DateTime.now().millisecondsSinceEpoch} onDone);});Stream.fromFutures([Future.delayed(Duration(seconds: 1),(){return 事件1;}),Future.delayed(Duration(seconds: 3),(){return 事件2;}),Future.delayed(Duration(seconds: 5),(){return 事件3;})]).listen((event) {print(${DateTime.now().millisecondsSinceEpoch} event);},onError: (error){},onDone: (){});运行结果
1703817812594 事件1
1703817814583 事件2 //2s后打印
1703817816574 事件3 //2s后打印
1703817816578 onDone另外一种使用方式 更加灵活
var streamController StreamController();streamController.stream.listen((event) {print(event);});streamController.add(事件1);streamController.add(事件2);streamController.add(事件3);运行结果
事件1
事件2
事件3由结果可以看出Stream类似于rxjava Stream.listen()方法返回StreamSubscription 可用于取消事件订阅取消后不再接收事件 未取消订阅 StreamController streamController StreamController();StreamSubscription streamSubscription streamController.stream.listen((event) {print(event);});streamController.add(事件1);streamController.add(事件2);Future((){sleep(Duration(seconds: 2));// streamSubscription.cancel();streamController.add(事件3);});结果
事件1
事件2
事件3取消订阅后 StreamController streamController StreamController();StreamSubscription streamSubscription streamController.stream.listen((event) {print(event);});streamController.add(事件1);streamController.add(事件2);Future((){sleep(Duration(seconds: 2));streamSubscription.cancel();streamController.add(事件3);});结果
事件1
事件2StreamController
构造函数参数表示stream的生命周期
/**
onListen: 监听开始开始
onPause监听暂停
onResume:监听重启
onCancel监听取消
sync 同步 or 异步
*/factory StreamController({void onListen()?,void onPause()?,void onResume()?,FutureOrvoid onCancel()?,bool sync false}) {return sync? _SyncStreamControllerT(onListen, onPause, onResume, onCancel): _AsyncStreamControllerT(onListen, onPause, onResume, onCancel);}StreamController streamController StreamController(onListen: (){print(onListen);},onPause: (){print(onPause);},onResume: (){print(onResume);},onCancel: (){print(onCancel);},);StreamSubscription streamSubscription streamController.stream.listen((event) {print(event);});streamController.add(事件1);streamSubscription.pause();streamSubscription.resume();streamController.add(事件2);Future((){sleep(Duration(seconds: 2));streamSubscription.cancel();streamController.add(事件3);});运行结果
onListen
onPause
事件1
事件2
onResume
onCancelStream其他构造方法
void main() async{Stream.value(1).listen((event) {print(event);});Stream.fromIterable([2,3,4,5]).listen((event) {print(event);});//结合await使用Stream stream Stream.fromIterable([6,7,8,9]);await for(var i in stream){print(i);}
}运行结果
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9Stream.periodic 每隔多长时间执行一次任务 Stream.periodic(Duration(seconds: 2),(computationCount){return 它死啦它火啦它死啦才火啦${computationCount};}).take(5) //执行5次 不设置一直执行.listen((event) {print(event);});运行结果
它死啦它火啦它死啦才火啦0
它死啦它火啦它死啦才火啦1
它死啦它火啦它死啦才火啦2
它死啦它火啦它死啦才火啦3
它死啦它火啦它死啦才火啦4async* 标记的方法称为异步生成器,yield生成单个元素yield*生成多个元素最终汇集成流
void main(){createStream().listen((event) {print(${DateTime.now().millisecondsSinceEpoch} ${event});});
}Streamint createStream() async*{for(int i0;i10;i){sleep(Duration(seconds: 1)); //1s钟生成一个yield i;}
}//结果
1703821955894 0
1703821956912 1
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