flutter CheckedPopupMenuItem 选择项目后保持菜单打开

Question

我试图让菜单保持打开状态，以便我可以一次选择多个类别，而无需在每次选择后快速返回页面。

如果它可以像 Excel 过滤数据（或 Libreoffice Autofilter）那样运行就完美了

添加了截图

任何想法，将不胜感激！

当前应用程序 我的目标示例

代码：

import 'package:flutter/material.dart';

void main() {   return runApp(MaterialApp(
    home: MenuDemo(),   )); }

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

  static const String routeName = '/material/menu';

  @override   MenuDemoState createState() => new MenuDemoState(); }

class MenuDemoState extends State<MenuDemo> {   final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();

  final String _checkedValue1 = 'One';   final String _checkedValue2 = 'Two';   final String _checkedValue3 = 'Free';   final String
_checkedValue4 = 'Four';   List<String> _checkedValues;

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

  void showInSnackBar(String value) {
    _scaffoldKey.currentState
        .showSnackBar(new SnackBar(content: new Text(value)));   }

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

    showInSnackBar('Checked $_checkedValues');   }

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

  @override   Widget build(BuildContext context) {
    return new Scaffold(
        key: _scaffoldKey,
        body: Center(
          child: Container(
            width: 250.0,
            child: new ListTile(
                title: const Text(
                  'checklist menu',
                  textAlign: TextAlign.center,
                ),
                trailing: new PopupMenuButton<String>(
                    padding: EdgeInsets.zero,
                    onSelected: showCheckedMenuSelections,
                    itemBuilder: (BuildContext context) =>
                        <PopupMenuItem<String>>[
                          new CheckedPopupMenuItem<String>(
                              value: _checkedValue1,
                              checked: isChecked(_checkedValue1),
                              child: new Text(_checkedValue1)),
                          new CheckedPopupMenuItem<String>(
                              value: _checkedValue2,
                              //enabled: false,
                              checked: isChecked(_checkedValue2),
                              child: new Text(_checkedValue2)),
                          new CheckedPopupMenuItem<String>(
                              value: _checkedValue3,
                              checked: isChecked(_checkedValue3),
                              child: new Text(_checkedValue3)),
                          new CheckedPopupMenuItem<String>(
                              value: _checkedValue4,
                              checked: isChecked(_checkedValue4),
                              child: new Text(_checkedValue4))
                        ])),
          ),
        ));   } }

Answer 1

您可以创建自己的多选弹出菜单，因为使用默认的 PopupMenu 会在选择项目时关闭对话框。

class MultiSelectDialogItem<V> {
  const MultiSelectDialogItem(this.value, this.label);

  final V value;
  final String label;
}

class MultiSelectDialog<V> extends StatefulWidget {
  const MultiSelectDialog(
      {Key? key, required this.items, this.initialSelectedValues})
      : super(key: key);

  final List<MultiSelectDialogItem<V>> items;
  final Set<V>? initialSelectedValues;

  @override
  State<StatefulWidget> createState() => _MultiSelectDialogState<V>();
}

class _MultiSelectDialogState<V> extends State<MultiSelectDialog<V>> {
  final _selectedValues = <V>{};

  @override
  void initState() {
    super.initState();
    if (widget.initialSelectedValues != null) {
      _selectedValues.addAll(widget.initialSelectedValues!);
    }
  }

  void _onItemCheckedChange(V itemValue, bool checked) {
    setState(() {
      if (checked) {
        _selectedValues.add(itemValue);
      } else {
        _selectedValues.remove(itemValue);
      }
    });
  }

  void _onCancelTap() {
    Navigator.pop(context);
  }

  void _onSubmitTap() {
    Navigator.pop(context, _selectedValues);
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: const Text('Select items'),
      contentPadding: const EdgeInsets.only(top: 12.0),
      content: SingleChildScrollView(
        child: ListTileTheme(
          contentPadding: const EdgeInsets.fromLTRB(14.0, 0.0, 24.0, 0.0),
          child: ListBody(
            children: widget.items.map(_buildItem).toList(),
          ),
        ),
      ),
      actions: <Widget>[
        ElevatedButton(
          child: const Text('Cancel'),
          onPressed: _onCancelTap,
        ),
        ElevatedButton(
          child: const Text('Ok'),
          onPressed: _onSubmitTap,
        )
      ],
    );
  }

  Widget _buildItem(MultiSelectDialogItem<V> item) {
    final checked = _selectedValues.contains(item.value);
    return CheckboxListTile(
      value: checked,
      title: Text(item.label),
      controlAffinity: ListTileControlAffinity.leading,
      onChanged: (checked) =>
          _onItemCheckedChange(item.value, checked ?? false),
    );
  }
}

然后显示菜单。

void _showMultiSelect(BuildContext context) async {
  // set value and label on MultiSelectDialogItem 
  final items = <MultiSelectDialogItem<int>>[
    const MultiSelectDialogItem(1, 'Item 1'),
    const MultiSelectDialogItem(2, 'Item 2'),
    const MultiSelectDialogItem(3, 'Item 3'),
  ];

  final selectedValues = await showDialog<Set<int>>(
    context: context,
    builder: (BuildContext context) {
      return MultiSelectDialog(
        items: items,
        // use Set to configure initial selected value
        // i.e. initialSelectedValues: const {1,2}  
        initialSelectedValues: null,
      );
    },
  );

  // Fetch selected items
  debugPrint('Selected Values: $selectedValues');
}

完整样品

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

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

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

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  void _showMultiSelect(BuildContext context) async {
    final items = <MultiSelectDialogItem<int>>[
      const MultiSelectDialogItem(1, 'Item 1'),
      const MultiSelectDialogItem(2, 'Item 2'),
      const MultiSelectDialogItem(3, 'Item 3'),
    ];

    final selectedValues = await showDialog<Set<int>>(
      context: context,
      builder: (BuildContext context) {
        return MultiSelectDialog(
          items: items,
          initialSelectedValues: null,
        );
      },
    );

    debugPrint('Selected Values: $selectedValues');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            _showMultiSelect(context);
          },
          child: const Text('Show Dropdown Multiselect'),
        ),
      ),
    );
  }
}

class MultiSelectDialogItem<V> {
  const MultiSelectDialogItem(this.value, this.label);

  final V value;
  final String label;
}

class MultiSelectDialog<V> extends StatefulWidget {
  const MultiSelectDialog(
      {Key? key, required this.items, this.initialSelectedValues})
      : super(key: key);

  final List<MultiSelectDialogItem<V>> items;
  final Set<V>? initialSelectedValues;

  @override
  State<StatefulWidget> createState() => _MultiSelectDialogState<V>();
}

class _MultiSelectDialogState<V> extends State<MultiSelectDialog<V>> {
  final _selectedValues = <V>{};

  @override
  void initState() {
    super.initState();
    if (widget.initialSelectedValues != null) {
      _selectedValues.addAll(widget.initialSelectedValues!);
    }
  }

  void _onItemCheckedChange(V itemValue, bool checked) {
    setState(() {
      if (checked) {
        _selectedValues.add(itemValue);
      } else {
        _selectedValues.remove(itemValue);
      }
    });
  }

  void _onCancelTap() {
    Navigator.pop(context);
  }

  void _onSubmitTap() {
    Navigator.pop(context, _selectedValues);
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: const Text('Select items'),
      contentPadding: const EdgeInsets.only(top: 12.0),
      content: SingleChildScrollView(
        child: ListTileTheme(
          contentPadding: const EdgeInsets.fromLTRB(14.0, 0.0, 24.0, 0.0),
          child: ListBody(
            children: widget.items.map(_buildItem).toList(),
          ),
        ),
      ),
      actions: <Widget>[
        ElevatedButton(
          child: const Text('Cancel'),
          onPressed: _onCancelTap,
        ),
        ElevatedButton(
          child: const Text('Ok'),
          onPressed: _onSubmitTap,
        )
      ],
    );
  }

  Widget _buildItem(MultiSelectDialogItem<V> item) {
    final checked = _selectedValues.contains(item.value);
    return CheckboxListTile(
      value: checked,
      title: Text(item.label),
      controlAffinity: ListTileControlAffinity.leading,
      onChanged: (checked) =>
          _onItemCheckedChange(item.value, checked ?? false),
    );
  }
}