Question

我实际上正在尝试使用ObservableMap包在我的Flutter应用中听取地图上的更改，该应用已声明为Observable。

我使用StreamSubscription来通知任何更改。但问题是它没有在地图对象内部监听地图内部的变化。我已经包含了一个例子供参考。如果我做错了或者我们必须以不同的方式做这件事，请有人告诉我。

main.dart

    import 'dart:async';

import 'package:flutter/material.dart';
import 'package:observable_map_demo/globals.dart';
import 'package:observable_map_demo/second_screen.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(

        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Observable Demo'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {

  Map data = new Map();
  StreamSubscription changeListener;
  var change;

  @override
  void initState(){
    super.initState();
//    changeListener = observeMap.changes.listen((c){
//      setState((){
//        data = observeMap;
//        print('here');
//        print(c);
//
//      });
//    });

    change = observeMap.changes.forEach((c){
      setState((){
        print(c);
        data = observeMap;
        print('here in ');

      });

    }).whenComplete((){
      setState((){
        data = observeMap;
        print('here');

      });
    });


  }

  @override
  Widget build(BuildContext context) {

    return new Scaffold(
      appBar: new AppBar(

        title: new Text(widget.title),
      ),
      body: new Center(

        child: new Column(

          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
//            
          new Text(data.toString()),

            new MaterialButton(child: new Text('click for next screen'),onPressed: ()=>Navigator.push(context, new MaterialPageRoute(builder: (_)=> new SecondState())),)
          ],
        ),
      ),
       // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

globals.dart：

import 'package:observable/observable.dart';
ObservableMap observeMap = new ObservableMap();

second_screen.dart：

import 'package:flutter/material.dart';
import 'package:observable_map_demo/globals.dart';

class SecondState extends StatefulWidget {
  @override
  _SecondStateState createState() => new _SecondStateState();
}

class _SecondStateState extends State<SecondState> {
  int i=0;

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: new Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children:<Widget>[

          new MaterialButton(onPressed: ((){
            i++;

            setState((){
              Map x = {'prayuta':'hyd'};
              Map data1 = {'hey':x};

              Map data = {'hi': data1,
              'how':'hello world'};

              observeMap.addAll(data);
              print(observeMap);
            });

          }),
            child: new Text('Hi'+observeMap.toString()),
          ),

          new MaterialButton(onPressed: ((){
            setState((){
              observeMap['hi'].remove('hey');
              print(observeMap);
            });
          }),
            child: new Text('remove'+observeMap.toString()),
          ),

        ]


      ),
    );
  }
}

Answer 1

这是按预期工作的，可观察地图仅识别是否添加或删除了值或键，而不是当它所拥有的值的属性被修改时。

飞镖中的可观察包没有在地图上听取变化？

1 个答案: