flutter学习笔记二

Isolate--------------------------------------------------------

• 通过Isolate传递消息

void main() {
  runApp(MyApp());
  try {
    /**
     * ReceivePort
     */
    SendPort childSendPort;
    ReceivePort receivePort = new ReceivePort();
    Isolate.spawn(isolateMain, receivePort.sendPort);

    receivePort.listen((message) {
      if (message is SendPort) {
        print("这里收到  子线程  的发送器啦！");
        message.send(message);
        print("发送  主线程发送器");
        childSendPort = message;
      } else {
        print("这里收到  子线程  的消息啦！");
        if (childSendPort != null) {
          print("发送主线程消息");
          childSendPort.send("主线程消息");
        }
      }
    });
  } catch (e) {
    print(e); //输出-->异常:分母不可以为0
  }
}

void isolateMain(SendPort sendPort) {
  ReceivePort receivePort = new ReceivePort();
  sendPort.send(receivePort.sendPort);
  print("发送  子线程发送器");
  sendPort.send("子线程消息");
  print("发送子线程消息");
  receivePort.listen((message) {
    if (message is SendPort) {
      print("这里收到  主线程  的消息啦！${message}");
    } else {
      print("这里收到  主线程  的消息啦！${message}");
    }
  });
}

/**
*I/flutter: 发送  子线程发送器
*I/flutter: 发送子线程消息
*I/flutter: 发送  主线程发送器
*I/flutter: 这里收到  子线程  的发送器啦！
*I/flutter: 这里收到  子线程  的消息啦！
*I/flutter: 发送主线程消息
*I/flutter: 这里收到  主线程  的消息啦！SendPort
*I/flutter: 这里收到  主线程  的消息啦！主线程消息
*/

执行优先-------------------------------------------------------

• Future（优先执行及延时执行）

/**
     * 执行延时
     */
    Future.delayed(new Duration(seconds: 5), (){
      getUserInfo("22");
      saveUserInfo("delayed running");
    }).then((value){
      print("then running = ${value}");
    }).catchError((error){
      print("catch error = ${error}");
    });

    /**
     * 执行优先
     */
    Future.microtask((){
      login("jeck", "998899");
    });

    /**
     * 与构造函数同步执行
     */
    Future.sync((){
      print("sync running");
    });

//I/flutter: sync running
//I/flutter: user = jeck + 998899
//I/flutter: id = 22
//I/flutter: userinfo = delayed running
//I/flutter: then running = null

异步执行-------------------------------------------------------

• Future（优先执行及延时执行）

    /**
     * 异步执行
     */
    Stream.fromFutures([loginFuture, userInfoFuture, saveUserInfoFuture])
        .listen((data) {
          print("各个任务返回的结果回调${data}");
    },onError: ((err) {
          print("各个任务执行失败的回调${err}");
    }), onDone: ((){
          print("监听各个任务执行过程中完成回调");
    })).onDone((){
          print("所有任务全部完成的回调");
    });

Future loginFuture = Future((){
  login("name", "999");
});

String login(String name, String psw){
  print("user = ${name} + ${psw}");
}

Future userInfoFuture = Future((){
  getUserInfo("123");
});

String getUserInfo(String id){
  print("id = ${id}");
}

Future saveUserInfoFuture = Future((){
  saveUserInfo("user lisa");
});

String saveUserInfo(String info){
  print("userinfo = ${info}");
}

//I/flutter: user = name + 999
//I/flutter: 各个任务返回的结果回调null
//I/flutter: id = 123
//I/flutter: 各个任务返回的结果回调null
//I/flutter: userinfo = user lisa
//I/flutter: 各个任务返回的结果回调null
//I/flutter: 所有任务全部完成的回调

流传输------------------------------------------------------

• StreamController

    /**
     * 创建流
     */
    StreamController controller = StreamController();
    StreamSubscription subscription = controller.stream.listen((data) {
      Student getData = data as Student;
      String name = getData.name;
      int age = getData.age;
      print("name = ${name}, age = ${age}");
    });
    Student student = new Student("name", 22);
    controller.sink.add(student);

//I/flutter: name = name, age = 22

• StreamTransformer

    /**
     * 流转换  接收到数据后，进行处理再传给控制器
     */
    StreamController controller = StreamController();
    var transformer = StreamTransformer.fromHandlers(
      handleData: (value, sink) {
      if(value == 1) {
        sink.add("操作正确");
      } else {
        sink.addError("操作失败，再试一次吧");
      }
    });

  /**
   * 创建流 通过transform(transformer) 将流转换
   */
  controller.stream.transform(transformer).listen((data) {
      print(
      "controller data = ${data}");
      },
      onError: (err) {
      print(
      "controller err = ${err}");
     });

    controller.sink.add(Student("jack", 23));

//controller err = 操作失败，再试一次吧