The name 'State' is defined in the libraries 'package:flutter/src/widgets/framework.dart' and 'package:mongo_dart/mongo_dart.dart'.

[mima1993]

The name 'State' is defined in the libraries 'package:flutter/src/widgets/framework.dart' and 'package:mongo_dart/mongo_dart.dart'. The only way to resolve this problem is to change classname 'State' in mongo_dart.dart. Otherwise the following error always exists: I/flutter (11323): Caught error: MongoDB ConnectionException: Could not connect to the Data Base. E/flutter (11323): [ERROR:flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: MongoDart Error: Db is in the wrong state: State.OPENING

[giorgiofran]

You can either hide State from mongo_dart import: import 'package:mongo_dart/mongo_dart.dart' hide State; or assign a prefix to mongo_dart: import 'package:mongo_dart/mongo_dart.dart' as mongo; In this last case you will have to prefix all mongo_dart classes with "mongo" (ex. mongo.Db).

[mima1993]

Thanks for help!
I tried but it didn't work, the error occured because in lifetime of [State] widget it call mongo.Db, when running mongo_dart, [State] is ambiguous, unforuntly system treat it as the widget.

My program is list.dart:

import 'package:flutter/material.dart'; import 'package:mongo_dart/mongo_dart.dart' as mongo; import 'package:dio/dio.dart'; import 'detail.dart'; import 'adapt.dart';

Dio dio = Dio();

class TopicList extends StatefulWidget { //固定写法 TopicList({Key key, @required this.tpt}) : super(key: key);

//主题类别 final String tpt;

@override _TopicListState createState() { return _TopicListState(); } }

class _TopicListState extends State with AutomaticKeepAliveClientMixin { //页码 int page = 1; //每页条数 int pagesize = 10; //主题列表数据 var tplist = []; //主题条数 var total = 0;

@override bool get wantKeepAlive => true;

//控件被执行的时候会执行initState @override void initState() { super.initState(); getTopicList(); }

@override // ignore: must_call_super Widget build(BuildContext context) { return ListView.builder( itemCount: tplist.length, itemBuilder: (BuildContext ctx, int i) { //当前的主题item项 var tpitem = tplist[i]; return GestureDetector( onTap: () { //跳转到详情 Navigator.push(context, MaterialPageRoute(builder: (BuildContext ctx) { return TopicDetail(id: tpitem['_id'], title: tpitem['title']); })); }, child: Container( height: Adapt.px(200), decoration: BoxDecoration( color: Colors.white, border: Border(top: BorderSide(color: Colors.black12))), child: Row( children: [ Image.network( 'https://i01piccdn.sogoucdn.com/c54a9f0cbafea7a6', width: Adapt.px(130), height: Adapt.px(180), fit: BoxFit.cover, ), Container( padding: EdgeInsets.only( left: Adapt.px(10), ), height: Adapt.px(200), child: DefaultTextStyle( style: TextStyle( fontSize: Adapt.px(16), color: Colors.black87), child: Column( crossAxisAlignment: CrossAxisAlignment.start, mainAxisAlignment: MainAxisAlignment.spaceAround, children: [ Text('标题：${tpitem['title']}'), Text('内容：${tpitem['content']}'), Text('最新：${tpitem['result'].toString()}'), ], ))) ], ), )); }); }

//获取主题列表数据 getTopicList() async { var db = mongo.Db('mongodb://127.0.0.1/hzd'); try { await db.open(); print('Awaiting connecting...'); } catch (err) { print('Caught error: $err'); } var coll = db.collection('topics'); //服务器返回的数据 var result = await coll.find().toList(); //赋值，页面更新 setState(() { tplist.addAll(result); total = result.length; }); } }

[giorgiofran]

If you define it as I told the system will treat it as mongo.State. It must work. Which is exactly the error? The problem should be elsewhere.

[giorgiofran]

The following is an example of a working flutter program. It is a "fast and furious" app (modifying a Stagehand example) that I made in order to test Atlas connections, so please, don't look at the programming style, but look at the logic of the app:

import 'package:flutter/material.dart';
import 'package:mongo_dart/mongo_dart.dart' hide State;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  String atlasUrl = '';
  final _biggerFont = const TextStyle(fontSize: 18.0);
  final _actions = <String>[];
  final _saved = Set<String>();

  Widget _buildActions() {
    return Expanded(
        child: ListView.builder(
      padding: const EdgeInsets.all(16.0),
      itemCount: _actions.length,
      itemBuilder: (context, i) {
        return _buildRow(_actions[i]);
      },
    ));
  }

  Widget _buildRow(String log) {
    final alreadySaved = _saved.contains(log);
    return ListTile(
      title: Text(
        log,
        style: _biggerFont,
      ),
      trailing: Icon(
        alreadySaved ? Icons.favorite : Icons.favorite_border,
        color: alreadySaved ? Colors.red : null,
      ),
      onTap: () {
        setState(() {
          if (alreadySaved) {
            _saved.remove(log);
          } else {
            _saved.add(log);
          }
        });
      },
    );
  }
  // #enddocregion _buildRow

  void _connect() async {
    print('Urls is: $atlasUrl');
    _actions.clear();
    _saved.clear();
    try {
      var db = await Db.create(atlasUrl);
      _actions.add('Db created!');
      await db.open();
      _actions.add('Connected!');
      var coll = db.collection('flutter-test');
      var result = await coll.insertOne({'flutter': true});
      if (result['ok'] == 1.0) {
        _actions.add('Inserted!');
      } else {
        _actions.add(result['errmsg']);
      }
    } catch (e) {
      _actions.add('$e');
    } finally {
      setState(() {
        _counter++;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Column(
        children: <Widget>[
          TextField(
              decoration: InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Atlas Url',
              ),
              onSubmitted: (String value) async {
                atlasUrl = value;
              }),
          Text(
            'You have pushed the button this many times:',
          ),
          Text(
            '$_counter',
            style: Theme.of(context).textTheme.headline4,
          ),
          if (_actions.isNotEmpty) _buildActions()
        ],
      ),
      floatingActionButton: RaisedButton(
          onPressed: _connect,
          //tooltip: 'Increment',
          child: Text("Connect") //Icon(Icons.add),
          ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

[mima1993]

Thanks for reply. I tried your program and entered local Mongo database URI, I got the same error: I/flutter (16657): MongoDB ConnectionException: Could not connect to the Data Base. I think Mongodb in my PC is okay because I can add data using program with Mongo_Dart package. If you find a method to resolve the problem, please let me know.

[giorgiofran]

The connection Exception normally occurs when the URL is wrong and/or there is no authentication rights on the database. Eventually try to check the database log for more info

[giorgiofran]

I did some more test, and yes, I couldn't connect on localhost! If I tried to connect to another mongodb instance in my network (let's say 192.168.1.5), no problem, but localhost, it was not working. I guess that the problem is exactly that, inside the emulator the address 127.0.0.1 is the emulator itself! So, I tried the following workaround:

• Launched my local instance of mongo db with the option --bind_ip 127.0.0.1,<local_host_ip_address> . Example --bind_ip 127.0.0.1,192.168.1.10
• I gave the url with the computer address to the application, Ex. mongodb://192.168.1.10:27017/test This way it works! So, resuming, it seems that the emulator consider localhost as itself and not as the programmer computer. I'm not a flutter expert, so, maybe that there is some setting that could change this behaviour, or maybe that the cause is different, but to me it seems quite a logic consequence of emulating a device. If anyone else has a better explanation/solution we are waiting for your cents... ;-)

[giorgiofran]

Hope that you have solved your problem. I close the issue, feel free to reopen if needed.