本文向您展示了在 Flutter 中实现完美的验证码输入框几种不同方法。

重点是什么？

真实世界的 完美的验证码输入框或 PIN 输入 UI 通常满足以下最低要求：

• 有4个或6个文本域，每个文本域只能接受1个字符（通常是一个数字）

• 输入数字后自动聚焦下一个字段

您经常在需要电话号码确认、电子邮件或双因素身份验证的应用程序中看到此功能。

从头开始制作 OTP 字段

应用预览

此示例创建一个简单的 OTP 屏幕。首先，聚焦第一个输入字段。当您输入一个数字时，光标将自动移动到下一个字段。当按下提交按钮时，您输入的 OTP 代码将显示在屏幕上。

以下是它的工作原理：

测试此应用程序时，您应该使用模拟器的软键盘而不是计算机的硬件键盘。

代码

创建一个名为OtpInput的可重用小部件：

// Create an input widget that takes only one digit
class OtpInput extends StatelessWidget {
  final TextEditingController controller;
  final bool autoFocus;
  const OtpInput(this.controller, this.autoFocus, {Key? key}) : super(key: key);
​
  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: 60,
      width: 50,
      child: TextField(
        autofocus: autoFocus,
        textAlign: TextAlign.center,
        keyboardType: TextInputType.number,
        controller: controller,
        maxLength: 1,
        cursorColor: Theme.of(context).primaryColor,
        decoration: const InputDecoration(
            border: OutlineInputBorder(),
            counterText: '',
            hintStyle: TextStyle(color: Colors.black, fontSize: 20.0)),
        onChanged: (value) {
          if (value.length == 1) {
            FocusScope.of(context).nextFocus();
          }
        },
      ),
    );
  }
}

main.dart 中的完整源代码和解释（我将OtpInput类放在文件底部）：

import 'dart:math' as math;
​
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:async/async.dart';
import 'package:flutter/scheduler.dart';
import 'package:url_strategy/url_strategy.dart';
​
void main() {
  setPathUrlStrategy();
  runApp(MyApp());
}
​
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Hide the debug banner
      debugShowCheckedModeBanner: false,
      title: '坚果',
      theme: ThemeData(
        primarySwatch: Colors.indigo,
      ),
      home: const HomeScreen(),
    );
  }
}
​
class HomeScreen extends StatefulWidget {
  const HomeScreen({Key? key}) : super(key: key);
​
  @override
  State<HomeScreen> createState() => _HomeScreenState();
}
​
class _HomeScreenState extends State<HomeScreen> {
  String _imageUrl =
      'https://luckly007.oss-cn-beijing.aliyuncs.com/image/image-20211124085239175.png';
  double _fontSize = 20;
  String _title = "坚果公众号";
  // 4 text editing controllers that associate with the 4 input fields
  final TextEditingController _fieldOne = TextEditingController();
  final TextEditingController _fieldTwo = TextEditingController();
  final TextEditingController _fieldThree = TextEditingController();
  final TextEditingController _fieldFour = TextEditingController();
​
  // This is the entered code
  // It will be displayed in a Text widget
  String? _otp;
​
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(_title),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          const Text('请输入验证码'),
          const SizedBox(
            height: 30,
          ),
          // Implement 4 input fields
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: [
              OtpInput(_fieldOne, true),
              OtpInput(_fieldTwo, false),
              OtpInput(_fieldThree, false),
              OtpInput(_fieldFour, false)
            ],
          ),
          const SizedBox(
            height: 30,
          ),
          ElevatedButton(
              onPressed: () {
                setState(() {
                  _otp = _fieldOne.text +
                      _fieldTwo.text +
                      _fieldThree.text +
                      _fieldFour.text;
                });
              },
              child: const Text('提交')),
          const SizedBox(
            height: 30,
          ),
          // Display the entered OTP code
          Text(
            _otp ?? '验证码',
            style: const TextStyle(fontSize: 30),
          )
        ],
      ),
    );
  }
}
​
// Create an input widget that takes only one digit
class OtpInput extends StatelessWidget {
  final TextEditingController controller;
  final bool autoFocus;
  const OtpInput(this.controller, this.autoFocus, {Key? key}) : super(key: key);
​
  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: 60,
      width: 50,
      child: TextField(
        autofocus: autoFocus,
        textAlign: TextAlign.center,
        keyboardType: TextInputType.number,
        controller: controller,
        maxLength: 1,
        cursorColor: Theme.of(context).primaryColor,
        decoration: const InputDecoration(
            border: OutlineInputBorder(),
            counterText: '',
            hintStyle: TextStyle(color: Colors.black, fontSize: 20.0)),
        onChanged: (value) {
          if (value.length == 1) {
            FocusScope.of(context).nextFocus();
          }
        },
      ),
    );
  }
}
​

使用第三个包

为了仅用几行代码快速实现您的目标，您可以使用第三方插件。在我们的例子中一些好的是pin_code_fields，otp_text_field等。 下面的例子将使用pin_code_fileds，它提供了很多很棒的功能：

• 自动将下一个字段集中在打字上，将上一个字段集中在委派上

• 可以设置为任意长度

• 高度可定制

• 输入文本的 3 种不同类型的动画

• 动画活动、非活动、选定和禁用字段颜色切换

• 自动对焦选项

• 从剪贴板粘贴 OTP 代码

您还可以在终端窗口中看到您输入的字符：

代码

1.安装插件：

flutter pub add pin_code_fields

2.最终代码：

import 'dart:math' as math;
​
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:async/async.dart';
import 'package:pin_code_fields/pin_code_fields.dart';
import 'package:url_strategy/url_strategy.dart';
​
void main() {
  setPathUrlStrategy();
  runApp(MyApp());
}
​
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Hide the debug banner
      debugShowCheckedModeBanner: false,
      title: '坚果',
      theme: ThemeData(
        primarySwatch: Colors.indigo,
      ),
      home: const HomeScreen(),
    );
  }
}
​
class HomeScreen extends StatefulWidget {
  const HomeScreen({Key? key}) : super(key: key);
​
  @override
  State<HomeScreen> createState() => _HomeScreenState();
}
​
class _HomeScreenState extends State<HomeScreen> {
  String _imageUrl =
      'https://luckly007.oss-cn-beijing.aliyuncs.com/image/image-20211124085239175.png';
  double _fontSize = 20;
  String _title = "坚果公众号";
  // 4 text editing controllers that associate with the 4 input fields
  TextEditingController textEditingController = TextEditingController();
  String currentText = "";
​
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(_title),
      ),
      body: Padding(
        padding: const EdgeInsets.all(30),
        child: Center(
          child: PinCodeTextField(
            length: 6,
            obscureText: false,
            animationType: AnimationType.fade,
            pinTheme: PinTheme(
              shape: PinCodeFieldShape.box,
              borderRadius: BorderRadius.circular(5),
              fieldHeight: 50,
              fieldWidth: 40,
              activeFillColor: Colors.white,
            ),
            animationDuration: const Duration(milliseconds: 300),
            backgroundColor: Colors.blue.shade50,
            enableActiveFill: true,
            controller: textEditingController,
            onCompleted: (v) {
              debugPrint("Completed");
            },
            onChanged: (value) {
              debugPrint(value);
              setState(() {
                currentText = value;
              });
            },
            beforeTextPaste: (text) {
              return true;
            },
            appContext: context,
          ),
        ),
      ),
    );
  }
}
​

结论

我们已经介绍了 2 个在 Flutter 中创建现代优雅的 完美的验证码输入框/PIN 输入字段的示例。

关于作者：

坚果，目前是华为云享专家，51CTO 博客首席体验官，专注于大前端技术的分享，包括 Flutter,小程序,安卓，VUE，JavaScript。公众号有更多细节。