【Flutter 组件】005-基础组件：单选、开关和复选框

一、概述

Material 组件库中提供了 Material 风格的单选开关 Switch 和复选框 Checkbox，虽然它们都是继承自 StatefulWidget，但它们本身不会保存当前选中状态，选中状态都是由父组件来管理的。当Switch或Checkbox被点击时，会触发它们的onChanged回调，我们可以在此回调中处理选中状态改变逻辑。

当需要实现多个选项的单选功能时，可以使用 Radio 和RadioListTile组件。这些组件允许用户在一组选项中选择一个。

二、基本使用

1、开关

代码示例

import 'package:flutter/material.dart';

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => HomePageState();
}

class HomePageState extends State<HomePage> {
  bool _value = false;

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: Center(
        child: Switch(
          value: _value,
          activeColor: Colors.black,
          onChanged: (bool newValue) {
            setState(() {
              _value = newValue;
            });
          },
        ),
      ),
    );
  }
}

运行结果

2、复选框

代码示例

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

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => HomePageState();
}

class HomePageState extends State<HomePage> {
  bool _value1 = false;
  bool _value2 = false;
  bool _value3 = false;
  bool _value4 = false;

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: Column(
        children: [
          Checkbox(
            value: _value1,
            onChanged: (bool? newValue) {
              setState(() {
                _value1 = newValue!;
              });
            },
          ),
          CheckboxListTile(
            title: const Text('Checkbox 2'),
            value: _value2,
            onChanged: (bool? newValue) {
              setState(() {
                _value2 = newValue!;
              });
            },
          ),
          CheckboxMenuButton(
              value: _value3,
              onChanged: (bool? newValue) {
                setState(() {
                  _value3 = newValue!;
                });
              },
              child: const Text('Checkbox 3')),
          CupertinoCheckbox(
            value: _value4,
            onChanged: (bool? newValue) {
              setState(() {
                _value4 = newValue!;
              });
            },
          ),
        ],
      ),
    );
  }
}

运行结果

3、多个选项单选

代码示例

import 'package:flutter/material.dart';

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => HomePageState();
}

class HomePageState extends State<HomePage> {
  String? _selectedOption;

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          RadioListTile<String>(
            title: const Text('Option 1'),
            value: 'Option 1',
            groupValue: _selectedOption,
            onChanged: (String? newValue) {
              setState(() {
                _selectedOption = newValue;
              });
            },
          ),
          RadioListTile<String>(
            title: const Text('Option 2'),
            value: 'Option 2',
            groupValue: _selectedOption,
            onChanged: (String? newValue) {
              setState(() {
                _selectedOption = newValue;
              });
            },
          ),
          RadioListTile<String>(
            title: const Text('Option 3'),
            value: 'Option 3',
            groupValue: _selectedOption,
            onChanged: (String? newValue) {
              setState(() {
                _selectedOption = newValue;
              });
            },
          ),
        ],
      ),
    );
  }
}

运行结果

4、多个选项多选

代码示例

import 'package:flutter/material.dart';

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => HomePageState();
}

class HomePageState extends State<HomePage> {
  final List<String> _selectedOptions = [];

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          CheckboxListTile(
            title: const Text('Option 1'),
            value: _selectedOptions.contains('Option 1'),
            onChanged: (bool? value) {
              setState(() {
                if (value != null && value) {
                  _selectedOptions.add('Option 1');
                } else {
                  _selectedOptions.remove('Option 1');
                }
              });
            },
          ),
          CheckboxListTile(
            title: const Text('Option 2'),
            value: _selectedOptions.contains('Option 2'),
            onChanged: (bool? value) {
              setState(() {
                if (value != null && value) {
                  _selectedOptions.add('Option 2');
                } else {
                  _selectedOptions.remove('Option 2');
                }
              });
            },
          ),
          CheckboxListTile(
            title: const Text('Option 3'),
            value: _selectedOptions.contains('Option 3'),
            onChanged: (bool? value) {
              setState(() {
                if (value != null && value) {
                  _selectedOptions.add('Option 3');
                } else {
                  _selectedOptions.remove('Option 3');
                }
              });
            },
          ),
        ],
      ),
    );
  }
}

运行结果