/// @Author: 一凨
/// @Date: 2018-12-22 21:01:51
/// @Last Modified by: 一凨
/// @Last Modified time: 2018-12-27 15:37:04

import 'package:flutter/material.dart';

class CheckedPopupMenuItemDemo extends StatefulWidget {
  _CheckedPopupMenuItemDemoState createState() =>
      _CheckedPopupMenuItemDemoState();
}

class _CheckedPopupMenuItemDemoState extends State<CheckedPopupMenuItemDemo> {
  List<String> _checkedValues;

  final String _checkedValue1 = 'One';
  final String _checkedValue2 = 'Two';
  final String _checkedValue3 = 'Three';
  final String _checkedValue4 = 'Four';

  @override
  void initState() {
    super.initState();
    _checkedValues = <String>[_checkedValue3];
  }

  bool isChecked(String value) => _checkedValues.contains(value);

  void showCheckedMenuSelections(String value) {
    if (_checkedValues.contains(value)) {
      _checkedValues.remove(value);
    } else {
      _checkedValues.add(value);
    }

    Scaffold.of(context)
        .showSnackBar(SnackBar(content: Text('Checked $_checkedValues')));
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Theme.of(context).primaryColor,
      child: ListTile(
        title: const Text(
          'CheckedPopupMenuItem Demo',
          style: TextStyle(color: Colors.white),
        ),
        trailing: PopupMenuButton<String>(
          padding: EdgeInsets.zero,
          onSelected: showCheckedMenuSelections,
          icon: Icon(
            Icons.menu,
            color: Colors.white,
          ),
          itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
            CheckedPopupMenuItem<String>(
                value: _checkedValue1,
                checked: isChecked(_checkedValue1),
                child: Text(_checkedValue1)),
            CheckedPopupMenuItem<String>(
                value: _checkedValue2,
                enabled: false,
                checked: isChecked(_checkedValue2),
                child: Text(_checkedValue2)),
            CheckedPopupMenuItem<String>(
                value: _checkedValue3,
                checked: isChecked(_checkedValue3),
                child: Text(_checkedValue3)),
            CheckedPopupMenuItem<String>(
                value: _checkedValue4,
                checked: isChecked(_checkedValue4),
                child: Text(_checkedValue4))
          ],
        ),
      ),
    );
  }
}