Flutter Multi-select ChoiceChip with max selection

MultiSelectChoiceChipWithMaxSelection.dart

import 'package:flutter/material.dart';

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

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

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  List<String> reportList = [
    "Not relevant",
    "Illegal",
    "Spam",
    "Offensive",
    "Uncivil"
  ];

  List<String> selectedReportList = [];

  _showReportDialog() {
    showDialog(
        context: context,
        builder: (BuildContext context) {
          //Here we will build the content of the dialog
          return AlertDialog(
            title: Text("Report Video"),
            content: MultiSelectChip(
              reportList,
              onSelectionChanged: (selectedList) {
                setState(() {
                  selectedReportList = selectedList;
                });
              },
              maxSelection: 2,
            ),
            actions: <Widget>[
              FlatButton(
                child: Text("Report"),
                onPressed: () => Navigator.of(context).pop(),
              )
            ],
          );
        });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
              child: Text("Report"),
              onPressed: () => _showReportDialog(),
            ),
            Text(selectedReportList.join(" , ")),
          ],
        ),
      ),
    );
  }
}

class MultiSelectChip extends StatefulWidget {
  final List<String> reportList;
  final Function(List<String>)? onSelectionChanged;
  final Function(List<String>)? onMaxSelected;
  final int? maxSelection;

  MultiSelectChip(this.reportList, {this.onSelectionChanged, this.onMaxSelected, this.maxSelection});

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

class _MultiSelectChipState extends State<MultiSelectChip> {
  // String selectedChoice = "";
  List<String> selectedChoices = [];

  _buildChoiceList() {
    List<Widget> choices = [];

    widget.reportList.forEach((item) {
      choices.add(Container(
        padding: const EdgeInsets.all(2.0),
        child: ChoiceChip(
          label: Text(item),
          selected: selectedChoices.contains(item),
          onSelected: (selected) {
            if(selectedChoices.length == (widget.maxSelection  ?? -1) && !selectedChoices.contains(item)) {
              widget.onMaxSelected?.call(selectedChoices);
            } else {
              setState(() {
                selectedChoices.contains(item)
                  ? selectedChoices.remove(item)
                  : selectedChoices.add(item);
                widget.onSelectionChanged?.call(selectedChoices);
              });
            }
          },
        ),
      ));
    });

    return choices;
  }

  @override
  Widget build(BuildContext context) {
    return Wrap(
      children: _buildChoiceList(),
    );
  }
}