Dart13.异步-then,catchError,whenComplete

ex:

import 'dart:async';

void main(){

  new Future(() => futrueTask())
      .then((i) => 'abc$i')
      .then((m) => print('$m'))
      .then((_) => new Future.error('出错了'))
      .whenComplete(() => print('whenComplete'))
      .catchError((e) => print(e), test: (Object o)
  {
    print('test');
    return true; //返回true，会被catchError捕获，返回false就不会被捕获，依旧会报异常
  });
}

futrueTask(){
  return 10;
}

输出：

D:\flutter\bin\cache\dart-sdk\bin\dart.exe --enable-asserts --enable-vm-service:41526 D:\Code\Flutter\FlutterHello\flutter_app\lib\async.dart
lib/async.dart: Warning: Interpreting this as package URI, 'package:flutterapp/async.dart'.
Observatory listening on http://127.0.0.1:41526/gFvDtcAIxZo=/

abc10
whenComplete
test
出错了

Process finished with exit code 0

如果上面的return true修改成return false，输出就是下面的：

D:\flutter\bin\cache\dart-sdk\bin\dart.exe --enable-asserts --enable-vm-service:41560 D:\Code\Flutter\FlutterHello\flutter_app\lib\async.dart
lib/async.dart: Warning: Interpreting this as package URI, 'package:flutterapp/async.dart'.
Observatory listening on http://127.0.0.1:41560/4hLf05l5PgM=/

abc10
Unhandled exception:
出错了
whenComplete
test

Process finished with exit code 255