在颤抖中是否存在与“选择多个"选择项等效的窗口小部件? HTML中的元素 [英] Is there an equivalent widget in flutter to the "select multiple" element in HTML

问题描述

我正在扑扑地寻找一个等于的小部件

I am searching for a widget in flutter that is equal to

<select multiple=""></select>

扑朔迷离.

(针对网络)示例实现为材料CSS选择多个

An example implementation (for the web) is MaterializeCSS Select Multiple

如上所示，我应该能够提供项目列表(其中一些已被预先选择)，最后检索所选项目或地图或其他内容的列表.

As seen above I should be able to provide a list of items (with some of them preselected) and at the end retrieve a list of selected items or a map or something else.

非常感谢示例实现或指向文档的链接.

An example implementation or a link to a documentation is very appreciated.

推荐答案

我不认为Flutter中目前存在这样的小部件，但是您可以自己构建.

I don't think that a widget like that currently exists in Flutter, but you can build one yourself.

在屏幕空间有限的手机上，显示带有提交按钮的对话框可能很有意义，例如

On mobile phones with limited screen space it would probably make sense to display a dialog with a submit button, like this native Android dialog.

这是一个粗略的草图，说明如何用不到100行代码来实现这样的对话框:

Here is a rough sketch how to implement such a dialog in less than 100 lines of code:

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

  final V value;
  final String label;
}

class MultiSelectDialog<V> extends StatefulWidget {
  MultiSelectDialog({Key key, 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 = Set<V>();

  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: Text('Select animals'),
      contentPadding: EdgeInsets.only(top: 12.0),
      content: SingleChildScrollView(
        child: ListTileTheme(
          contentPadding: EdgeInsets.fromLTRB(14.0, 0.0, 24.0, 0.0),
          child: ListBody(
            children: widget.items.map(_buildItem).toList(),
          ),
        ),
      ),
      actions: <Widget>[
        FlatButton(
          child: Text('CANCEL'),
          onPressed: _onCancelTap,
        ),
        FlatButton(
          child: 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),
    );
  }
}

您可以像这样使用它:

void _showMultiSelect(BuildContext context) async {
  final items = <MultiSelectDialogItem<int>>[
    MultiSelectDialogItem(1, 'Dog'),
    MultiSelectDialogItem(2, 'Cat'),
    MultiSelectDialogItem(3, 'Mouse'),
  ];

  final selectedValues = await showDialog<Set<int>>(
    context: context,
    builder: (BuildContext context) {
      return MultiSelectDialog(
        items: items,
        initialSelectedValues: [1, 3].toSet(),
      );
    },
  );

  print(selectedValues);
}

这篇关于在颤抖中是否存在与“选择多个"选择项等效的窗口小部件? HTML中的元素的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！