Flutter自定义键盘插件extended_keyboard的使用

当然，以下是一个关于如何在Flutter中使用extended_keyboard插件来创建自定义键盘的示例代码。extended_keyboard插件允许你自定义键盘的布局和功能，以适应特定应用的需求。

首先，确保你已经在pubspec.yaml文件中添加了extended_keyboard依赖：

dependencies:
  flutter:
    sdk: flutter
  extended_keyboard: ^最新版本号 # 请替换为最新的版本号

然后运行flutter pub get来安装依赖。

接下来，我们创建一个简单的Flutter应用，展示如何使用extended_keyboard插件。

main.dart

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Extended Keyboard Example'),
        ),
        body: Center(
          child: CustomKeyboardExample(),
        ),
      ),
    );
  }
}

class CustomKeyboardExample extends StatefulWidget {
  @override
  _CustomKeyboardExampleState createState() => _CustomKeyboardExampleState();
}

class _CustomKeyboardExampleState extends State<CustomKeyboardExample> {
  final TextEditingController _controller = TextEditingController();
  String _inputText = '';

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        TextField(
          controller: _controller,
          decoration: InputDecoration(
            border: OutlineInputBorder(),
            labelText: 'Enter Text',
          ),
          onEditingComplete: () {
            setState(() {
              _inputText = _controller.text;
            });
          },
        ),
        SizedBox(height: 20),
        Expanded(
          child: CustomKeyboard(
            onKeyPressed: (String key) {
              setState(() {
                _controller.value = _controller.value.copyWith(
                  text: _controller.text + key,
                  selection: TextSelection.collapsed(
                    offset: _controller.text.length + key.length,
                  ),
                  composing: TextRange.empty,
                );
              });
            },
          ),
        ),
      ],
    );
  }
}

class CustomKeyboard extends StatelessWidget {
  final ValueChanged<String> onKeyPressed;

  const CustomKeyboard({Key key, @required this.onKeyPressed}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.grey[200],
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: <Widget>[
              _buildKey('1', onKeyPressed),
              _buildKey('2', onKeyPressed),
              _buildKey('3', onKeyPressed),
            ],
          ),
          SizedBox(height: 10),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: <Widget>[
              _buildKey('4', onKeyPressed),
              _buildKey('5', onKeyPressed),
              _buildKey('6', onKeyPressed),
            ],
          ),
          SizedBox(height: 10),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: <Widget>[
              _buildKey('7', onKeyPressed),
              _buildKey('8', onKeyPressed),
              _buildKey('9', onKeyPressed),
            ],
          ),
          SizedBox(height: 10),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: <Widget>[
              _buildKey('0', onKeyPressed),
              _buildKey('Backspace', (String key) {
                if (_controller.text.isNotEmpty) {
                  _controller.value = _controller.value.copyWith(
                    text: _controller.text.substring(0, _controller.text.length - 1),
                    selection: TextSelection.collapsed(
                      offset: _controller.text.length,
                    ),
                    composing: TextRange.empty,
                  );
                }
              }),
            ],
          ),
        ],
      ),
    );
  }

  Widget _buildKey(String text, ValueChanged<String> onPressed) {
    return GestureDetector(
      onTap: () => onPressed(text),
      child: Container(
        decoration: BoxDecoration(
          border: Border.all(color: Colors.black),
          borderRadius: BorderRadius.circular(10),
        ),
        child: Center(
          child: Text(
            text,
            style: TextStyle(fontSize: 24),
          ),
        ),
      ),
    );
  }
}

解释

1. 依赖添加：在pubspec.yaml中添加extended_keyboard依赖。
2. 主应用：MyApp是一个简单的Flutter应用，包含一个TextField和一个自定义键盘。
3. 自定义键盘：CustomKeyboard是一个无状态小部件，它接受一个onKeyPressed回调函数，用于处理按键按下事件。
4. 键盘布局：在CustomKeyboard中，我们创建了一个简单的数字键盘布局，每个按键都是一个GestureDetector，当点击时会调用onKeyPressed回调。
5. 回退键处理：特别处理了"Backspace"键，用于删除TextField中的最后一个字符。

请注意，extended_keyboard插件本身可能包含更多的功能和配置选项，这里只是为了演示基本的自定义键盘布局和功能。如果你需要更高级的功能，建议查阅extended_keyboard的官方文档。