Q:

Flutter TypeAhead Issue

I am trying to implement the Flutter Typeahead based on the following link:
Flutter TypeAhead
 class _CallAddState extends State<CallAdd> {

     final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
     final TextEditingController _typeAheadController = TextEditingController();

    var SerVerConfig = [
    {
     "name":"Mike",
      "id":"1"
    },
    {
      "name":"Bill",
      "id":"2"
    },
    {
      "name":"Juan",
      "id":"3"
    },

  ];

   @override
   Widget build(BuildContext context) {
       return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: Form(
          key: this._formKey,
          child: Padding(
            padding: EdgeInsets.all(32.0),
            child: Column(
              children: <Widget>[
                TypeAheadField(
                  textFieldConfiguration: TextFieldConfiguration(
                      autofocus: true,
                      style: DefaultTextStyle.of(context)
                          .style
                          .copyWith(fontStyle: FontStyle.italic),
                      decoration:
                          InputDecoration(border: OutlineInputBorder())),
                  suggestionsCallback: (pattern) async {
                    return SerVerConfig;
                  },
                  itemBuilder: (context, suggestion) {
                    print("item builder " + suggestion);
                    return ListTile(
                      leading: Icon(Icons.shopping_cart),
                      title: Text(suggestion['name']),
//                      subtitle: Text('\$${suggestion['id']}'),
                    );
                  },
                  onSuggestionSelected: (suggestion) {
                    Navigator.of(context).push(MaterialPageRoute(
                        //  builder: (context) => ProductPage(product: suggestion)
                        ));
                  },
                )
              ],
            ),
          ),
        ));
    }
    }

Unfortunately, I am getting an error with the following message in the suggestionsCallback function.
"type '_InternalLinkedHashMap' is not a subtype of type 'String'
Any help or advice is much appreciated. 
Thanks.

A:

SerVerConfig use List, you can compare difference 
You can see full code and demo picture (Example 2: Form) 
code snippet 
 List SerVerConfig = [
    {"name": "Mike", "id": "1"},
    {"name": "Bill", "id": "2"},
    {"name": "Juan", "id": "3"},
  ];

TypeAheadField(
              textFieldConfiguration: TextFieldConfiguration(
                  autofocus: true,
                  style: DefaultTextStyle.of(context)
                      .style
                      .copyWith(fontStyle: FontStyle.italic),
                  decoration: InputDecoration(border: OutlineInputBorder())),
              suggestionsCallback: (pattern) async {
                return SerVerConfig;
              },
              itemBuilder: (context, suggestion) {
                return ListTile(
                  leading: Icon(Icons.shopping_cart),
                  title: Text(suggestion['name']),
//                      subtitle: Text('\$${suggestion['id']}'),
                );
              },
              onSuggestionSelected: (suggestion) {
                Navigator.of(context).push(MaterialPageRoute(
                    builder: (context) => ProductPage(product: suggestion)));
              },
            ),

full code
import 'package:flutter/material.dart';
import 'package:flutter_typeahead/flutter_typeahead.dart';

import 'package:example/data.dart';

class MyMaterialApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'flutter_typeahead demo',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: 3,
      child: Scaffold(
          appBar: AppBar(
            title: TabBar(tabs: [
              Tab(text: 'Example 1: Navigation'),
              Tab(text: 'Example 2: Form'),
              Tab(text: 'Example 3: Scroll')
            ]),
          ),
          body: TabBarView(children: [
            NavigationExample(),
            FormExample(),
            ScrollExample(),
          ])),
    );
  }
}

class NavigationExample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.all(32.0),
      child: Column(
        children: <Widget>[
          SizedBox(
            height: 10.0,
          ),
          TypeAheadField(
            textFieldConfiguration: TextFieldConfiguration(
              autofocus: true,
              style: DefaultTextStyle.of(context)
                  .style
                  .copyWith(fontStyle: FontStyle.italic),
              decoration: InputDecoration(
                  border: OutlineInputBorder(),
                  hintText: 'What are you looking for?'),
            ),
            suggestionsCallback: (pattern) async {
              var fruits = ['bananas', 'apples', 'oranges'];
              return await BackendService.getSuggestions(pattern);
            },
            itemBuilder: (context, suggestion) {
              return ListTile(
                leading: Icon(Icons.shopping_cart),
                title: Text(suggestion['name']),
                subtitle: Text('\$${suggestion['price']}'),
              );
            },
            onSuggestionSelected: (suggestion) {
              Navigator.of(context).push(MaterialPageRoute(
                  builder: (context) => ProductPage(product: suggestion)));
            },
          ),
        ],
      ),
    );
  }
}

class FormExample extends StatefulWidget {
  @override
  _FormExampleState createState() => _FormExampleState();
}

class _FormExampleState extends State<FormExample> {
  final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
  final TextEditingController _typeAheadController = TextEditingController();

  String _selectedCity;
  List SerVerConfig = [
    {"name": "Mike", "id": "1"},
    {"name": "Bill", "id": "2"},
    {"name": "Juan", "id": "3"},
  ];

  @override
  Widget build(BuildContext context) {
    return Form(
      key: this._formKey,
      child: Padding(
        padding: EdgeInsets.all(32.0),
        child: Column(
          children: <Widget>[
            Text('What is your favorite city?'),
            TypeAheadFormField(
              textFieldConfiguration: TextFieldConfiguration(
                decoration: InputDecoration(labelText: 'City'),
                controller: this._typeAheadController,
              ),
              suggestionsCallback: (pattern) {
                //var fruits = ['bananas', 'apples', 'oranges'];
                return CitiesService.getSuggestions(pattern);
              },
              itemBuilder: (context, suggestion) {
                return ListTile(
                  title: Text(suggestion),
                );
              },
              transitionBuilder: (context, suggestionsBox, controller) {
                return suggestionsBox;
              },
              onSuggestionSelected: (suggestion) {
                this._typeAheadController.text = suggestion;
              },
              validator: (value) {
                if (value.isEmpty) {
                  return 'Please select a city';
                }
              },
              onSaved: (value) => this._selectedCity = value,
            ),
            TypeAheadField(
              textFieldConfiguration: TextFieldConfiguration(
                  autofocus: true,
                  style: DefaultTextStyle.of(context)
                      .style
                      .copyWith(fontStyle: FontStyle.italic),
                  decoration: InputDecoration(border: OutlineInputBorder())),
              suggestionsCallback: (pattern) async {
                return SerVerConfig;
              },
              itemBuilder: (context, suggestion) {
                return ListTile(
                  leading: Icon(Icons.shopping_cart),
                  title: Text(suggestion['name']),
//                      subtitle: Text('\$${suggestion['id']}'),
                );
              },
              onSuggestionSelected: (suggestion) {
                Navigator.of(context).push(MaterialPageRoute(
                    builder: (context) => ProductPage(product: suggestion)));
              },
            ),
            SizedBox(
              height: 10.0,
            ),
            RaisedButton(
              child: Text('Submit'),
              onPressed: () {
                if (this._formKey.currentState.validate()) {
                  this._formKey.currentState.save();
                  Scaffold.of(context).showSnackBar(SnackBar(
                      content:
                          Text('Your Favorite City is ${this._selectedCity}')));
                }
              },
            )
          ],
        ),
      ),
    );
  }
}

class ScrollExample extends StatelessWidget {
  final List<String> items = List.generate(5, (index) => "Item $index");

  @override
  Widget build(BuildContext context) {
    return ListView(children: [
      Center(
          child: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Text("Suggestion box will resize when scrolling"),
      )),
      SizedBox(height: 200),
      TypeAheadField<String>(
        getImmediateSuggestions: true,
        textFieldConfiguration: TextFieldConfiguration(
          decoration: InputDecoration(
              border: OutlineInputBorder(),
              hintText: 'What are you looking for?'),
        ),
        suggestionsCallback: (String pattern) async {
          return items
              .where((item) =>
                  item.toLowerCase().startsWith(pattern.toLowerCase()))
              .toList();
        },
        itemBuilder: (context, String suggestion) {
          return ListTile(
            title: Text(suggestion),
          );
        },
        onSuggestionSelected: (String suggestion) {
          print("Suggestion selected");
        },
      ),
      SizedBox(height: 500),
    ]);
  }
}

class ProductPage extends StatelessWidget {
  final Map<String, dynamic> product;

  ProductPage({this.product});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Padding(
        padding: const EdgeInsets.all(50.0),
        child: Column(
          children: [
            Text(
              this.product['name'],
              style: Theme.of(context).textTheme.headline,
            ),
            Text(
              this.product['price'].toString() + ' USD',
              style: Theme.of(context).textTheme.subhead,
            )
          ],
        ),
      ),
    );
  }
}

