Should be able to implement queryBuilder about searchable_dropdown HOT 4 CLOSED

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

class OilProducer {
  String name;
  int id;

  OilProducer({this.name, this.id});

  OilProducer.fromJson(json) {
    name = json['name'];
    id = json['id'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['name'] = this.name;
    data['id'] = this.id;
    return data;
  }

  String toString(){
    return(name);
  }
}

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

  List<OilProducer> oilProducers = [];
  OilProducer selectedOilProducer;

  @override
  void initState() {
    oilProducers.add(OilProducer(name:"Petronas",id:1));
    oilProducers.add(OilProducer(name:"Petrobras",id:2));
    oilProducers.add(OilProducer(name:"Trebol",id:3));
    oilProducers.add(OilProducer(name:"AGIP",id:4));
    super.initState();
  }

  _dropSearch() {
    return new SearchableDropdown<OilProducer>(
      isCaseSensitiveSearch: true,
      items: oilProducers.map((fab) {
        return DropdownMenuItem<OilProducer>(
          child: new Text(fab.name),
          value: fab,
        );
      }).toList(),
      value: selectedOilProducer,
      hint: new Text('Select One'),
      searchHint: new Text(
        'Select One',
        style: new TextStyle(fontSize: 20),
      ),
      onChanged: (OilProducer value) {
        setState(() {
          this.selectedOilProducer = value;
        });
      },
      displayClearButton: true,
      validator: (value){return(value==null?"Mandatory":null);},
      label: (value){return("Oil producer");},
      keyboardType: TextInputType.text,
      searchFn: (String keyword, List<DropdownMenuItem<OilProducer>> items) {
        List<int> ret = List<int>();
        if (keyword != null && items != null) {
          keyword.split(" ").forEach((k) {
            int i = 0;
            items.forEach((item) {
              if (keyword.isEmpty || (k.isNotEmpty &&
                  (item.value.name.toLowerCase().contains(k.toLowerCase()) ||
                      item.value.id.toString().contains(k)))) {
                ret.add(i);
              }
              i++;
            });
          });
        }
        if(keyword.isEmpty){
          ret = Iterable<int>.generate(items.length).toList();
        }
        return (ret);
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Searchable Dropdown Demo'),
        ),
        resizeToAvoidBottomPadding: false,
        body: Padding(
          padding: const EdgeInsets.all(15.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              _dropSearch(),
            ],
          ),
        ),
      ),
    );
  }
}