flutter - 未处理的异常：'package：flutter/src/widgets/basic.dart'：断言失败：第 7419 行 pos 15：'child != null'：不正确

Question

尝试点击搜索时，抛出此错误：

'package：flutter/src/widgets/basic.dart'：断言失败：第 7419 行 pos 15：'child != null'：不正确。另见： http: //flutter.dev/docs/testing/errors

我不明白为什么会这样。

发布规范.yaml

 google_maps_flutter: "^2.0.1"
 flutter_google_places: "^0.3.0"

主页.dart

class HomeScreen extends StatefulWidget {
  const HomeScreen({Key key}) : super(key: key);

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

class _HomeScreenState extends State<HomeScreen> {

  final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
  final _searchCon = TextEditingController();

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

    locatePosition();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
          key: _scaffoldKey,
          drawer: buildDrawer(context),
          body: Stack(
            children: [
              GoogleMap(
                onMapCreated: _onMapCreated,
                markers: _markers,
                onCameraMove: _onCameraMove,
              ),
              TextField(
                controller: _searchCon,
                readOnly: true,
                onTap: () async {
                  final sessionToken = Uuid().v4();
                  final Suggestions result = await showSearch(
                    context: context,
                    delegate: PlacesSearch(sessionToken),
                  );
                  if (result != null) {
                    setState(() {
                      _searchCon.text = result.placeDesc;
                    });
                  }
                },
                decoration: InputDecoration(
                  icon: Container(
                    margin: EdgeInsets.only(left: 20),
                    width: 10,
                    height: 10,
                    child: Icon(
                      Icons.search,
                      color: Colors.black,
                    ),
                  ),
                  hintText: "Search ....",
                  border: InputBorder.none,
                  contentPadding: EdgeInsets.only(left: 8.0, top: 16.0),
                ),
              ),
            ],
          )),
    );
  }

也无法在 listview 上填充 Google Places API

class PlacesSearch extends SearchDelegate<Suggestions> {
  PlacesSearch(this.sessionToken) {
    apiClient = PlaceApiProvider(sessionToken);
  }

  final sessionToken;
  PlaceApiProvider apiClient;

  @override
  List<Widget> buildActions(BuildContext context) {
    return [
      IconButton(
        tooltip: 'Clear',
        icon: Icon(Icons.clear),
        onPressed: () => query = '',
      ),
    ];
  }

  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: Icon(Icons.arrow_back),
      onPressed: () => close(context, null),
    );
  }

  @override
  Widget buildResults(BuildContext context) {
    return null;
  }

  @override
  Widget buildSuggestions(BuildContext context) {
    return FutureBuilder(
      future: query.isEmpty
          ? null
          : apiClient.fetchSuggestions(
              query, Localizations.localeOf(context).languageCode),
      builder: (context, snapshot) => query.isEmpty
          ? Container(
              padding: EdgeInsets.all(16.0),
              child: Text('hello'),
            )
          : snapshot.hasData
              ? ListView.builder(
                  itemBuilder: (context, index) => ListTile(
                    //display data returned from our future
                    title:
                        Text((snapshot.data[index] as Suggestions).placeDesc),
                    onTap: () {
                      close(context, snapshot.data[index] as Suggestions);
                    },
                  ),
                  itemCount: snapshot.data.length,
                )
              : Container(child: Text('Loading .....')),
    );
  }
}

class PlaceApiProvider {
  final client = Client();
  PlaceApiProvider(this.sessionToken);

  final sessionToken;

  static final String androidKey = 'API_KEY';
  static final String iosKey = 'API_KEY';

  final apiKey = Platform.isAndroid ? androidKey : iosKey;

  Future<List<Suggestions>> fetchSuggestions(String input, String lang) async {
    final request =
        'https://maps.googleapis.com/maps/api/place/autocomplete/json?input=$input&types=address&language=$lang&components=country:ch&key=$apiKey&sessiontoken=$sessionToken';
    final response = await client.get(Uri.parse(request));

    if (response.statusCode == 200) {
      final result = json.decode(response.body);
      if (result['status'] == 'OK') {
        return result['predictions']
            .map<Suggestions>(
                (p) => Suggestions(p['place_id'], p['description']))
            .toList();
      }
      if (result['status'] == 'ZERO_RESULTS') {
        return [];
      }
      throw Exception(result['error_message']);
    } else {
      throw Exception('Failed to fetch suggestion');
    }
  }
}

建议课

class Suggestions {
  final String placeId;
  final String placeDesc;

  Suggestions(this.placeId, this.placeDesc);

  @override
  String toString() {
    // TODO: implement toString
    return 'Suggestions(description: $placeDesc, placeId: $placeId)';
  }
}

标签： fluttergoogle-places-apigoogle-placesgoogle-maps-flutter