Число не меняется после обновления в setState (), оно вызывается в конструкторе - PullRequest
0 голосов
/ 09 июля 2020

Контекст

У меня есть приложение на Kotlin (собственный Android), и оно отправляет данные в подключенный модуль во Flutter. Из Kotlin я отправляю _numA2F , и я хочу показать его в режиме флаттера, но он не работает. Другая переменная (_numF2A), которую я собираюсь отправить обратно в собственное приложение, обновляется правильно.

Вопрос

Не могли бы вы указать, почему _numA2F не Не берете значение, полученное из родного приложения android? Я уже подтвердил, что номер, который я отправляю с Kotlin, получен в модуле flutter.

Это мой код во Flutter:

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or press Run > Flutter Hot Reload in a Flutter IDE). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _numA2F = 1;
  int _numF2A = 1;

  static const platform = const MethodChannel('com.jssm.af/data');

  _MyHomePageState() {
    platform.setMethodCallHandler(_receiveFromHost);
  }

  Future<void> _receiveFromHost(MethodCall call) async {
    int number = 11;

    try {
      print('CHECK THIS OUT!!!!!!!!!');
      print(call.method);
      if (call.method == "fromHostToClient") {
        final String data = call.arguments;
        print(call.arguments);
        final jData = jsonDecode(data);
        number = jData['numA2F'];
      }
    } on PlatformException catch (e) {
      print(e);
    }

    setState(() {
      _numA2F = number;
      print("_numberA2F: " + _numA2F.toString());
    });

  }

  void _doubleNumber() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _numF2A = 2 * _numA2F;
    });
  }

  @override
  Widget build(BuildContext context) {
    print('REBUILDING!!!!!!!!!!');
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'Data received from fa_Android',
            ),
            Text(
              '$_numA2F',
              style: Theme.of(context).textTheme.headline4,
            ),
            Text(
              'Number to be returned (double):',
            ),
            Text(
              '$_numF2A',
              style: Theme.of(context).textTheme.headline4,
            ),
            RaisedButton(
              onPressed: _doubleNumber,
              child: const Text('Send Result to Android',
                  style: TextStyle(fontSize: 20)),
            )
          ],
        ),
      ),
    );
  }
}

1 Ответ

0 голосов
/ 09 июля 2020

Удалите это:

_MyHomePageState() {
    platform.setMethodCallHandler(_receiveFromHost);
  }

И используйте функцию initState, например:

@override
  void initState() {
  _receiveFromHost(call);
}

или еще лучше:

_MyHomePageState() {
    _receiveFromHost(call);
  }

...