Flutter软键盘按键检测回调：自定义触觉振动实现遇阻求助

Flutter框架本身没有提供直接监听系统软键盘按键按下的API，你之前尝试的FocusNode、RawKeyboardListener等方法仅对硬件键盘生效，系统软键盘的事件不会通过这些回调传递。要实现需求，必须通过自定义iOS原生插件来捕捉软键盘按键事件，再传递给Flutter触发振动。

具体实现步骤 #

1. 自定义Flutter插件（iOS端） #

通过方法交换（Swizzling）Hook系统输入控件的按键事件，将事件传递给Flutter，也可以直接在原生端触发触觉振动。

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    let controller = window?.rootViewController as! FlutterViewController
    let hapticChannel = FlutterMethodChannel(name: "com.yourdomain.haptic_keyboard", binaryMessenger: controller.binaryMessenger)
    
    // 交换UITextView的keyDown方法，捕捉按键事件
    let originalSelector = #selector(UITextView.keyDown(_:))
    let swizzledSelector = #selector(UITextView.swizzled_keyDown(_:))
    
    if let originalMethod = class_getInstanceMethod(UITextView.self, originalSelector),
       let swizzledMethod = class_getInstanceMethod(UITextView.self, swizzledSelector) {
      method_exchangeImplementations(originalMethod, swizzledMethod)
    }
    
    // 保存MethodChannel供交换后的方法调用
    HapticChannel.shared.channel = hapticChannel
    
    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

// 全局存储MethodChannel
class HapticChannel {
  static let shared = HapticChannel()
  var channel: FlutterMethodChannel?
}

extension UITextView {
  @objc func swizzled_keyDown(_ key: UIKey) {
    // 先调用原方法保证正常输入逻辑
    self.swizzled_keyDown(key)
    
    // 方式1：给Flutter发送事件，由Flutter触发振动
    HapticChannel.shared.channel?.invokeMethod("keyPressed", arguments: nil)
    
    // 方式2：直接在原生端触发触觉振动（延迟更低）
    let generator = UIImpactFeedbackGenerator(style: .light)
    generator.impactOccurred()
  }
}

2. Flutter端接收事件并触发振动 #

通过MethodChannel监听原生传递的按键事件，调用你的自定义振动插件。

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

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

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final MethodChannel _hapticChannel = const MethodChannel('com.yourdomain.haptic_keyboard');
  final FocusNode _focusNode = FocusNode();

  @override
  void initState() {
    super.initState();
    // 监听原生传递的按键事件
    _hapticChannel.setMethodCallHandler((call) async {
      if (call.method == 'keyPressed') {
        // 调用你的自定义振动插件
        HapticsPlugin().click();
      }
    });
  }

  @override
  void dispose() {
    _focusNode.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: const Text('软键盘触觉反馈')),
        body: Center(
          child: EditableText(
            focusNode: _focusNode,
            controller: TextEditingController(),
            style: const TextStyle(fontSize: 16),
            cursorColor: Colors.blue,
            backgroundCursorColor: Colors.grey,
          ),
        ),
      ),
    );
  }
}

// 你的自定义振动插件类
class HapticsPlugin {
  void click() {
    // 这里是你的振动实现逻辑
    print('触发触觉振动');
  }
}

关键说明 #

• 方法交换（Swizzling）需谨慎：如果你的项目中有其他第三方库也修改了UITextView的keyDown方法，可能会产生冲突。可以添加判断，仅对Flutter专属的输入控件（如FlutterTextInputView）生效。
• 原生端直接振动：在iOS端直接触发振动可以减少跨平台通信的延迟，体验更流畅。
• 兼容性：上述代码适配iOS 13+，低版本需使用旧版keyDown(_ event: UIEvent?)方法。

内容的提问来源于stack exchange，提问作者Mikael Wills