Flutter应用被杀重启后Method Channel未创建，无法调用Native代码求助

应用被杀重启后出现Tried to send a platform message to Flutter, but FlutterJNI was detached from native C++. Could not send. Channel: com.example.inyourskin. Response ID:报错，本质是应用重启后Native端的FlutterJNI实例失效，原Method Channel绑定关系丢失，导致无法通信。以下是分平台的修复方案：

Android端修复 #

• 在configureFlutterEngine中初始化Method Channel
  应用重启时Flutter引擎会重新初始化，configureFlutterEngine会被触发，这是绑定Channel的正确时机，不要在onCreate等早期生命周期方法中创建：

  class MainActivity : FlutterActivity() {
    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        // 初始化Method Channel并设置回调
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, "com.example.inyourskin")
            .setMethodCallHandler { call, result ->
                when (call.method) {
                    "yourTargetMethod" -> {
                        // 执行Native逻辑并返回结果
                        result.success("处理完成")
                    }
                    else -> result.notImplemented()
                }
            }
    }
  }
  

• 别用静态引用存FlutterEngine/Channel
  静态变量会持有旧的失效实例，重启后无法绑定新引擎，必须避免。

iOS端修复 #

• 在didFinishLaunchingWithOptions中重新绑定Channel
  应用被杀重启时didFinishLaunchingWithOptions会重新执行，在这里确保Channel和新的FlutterViewController绑定：

  @UIApplicationMain
  @objc class AppDelegate: FlutterAppDelegate {
    override func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        guard let controller = window?.rootViewController as? FlutterViewController else {
            return super.application(application, didFinishLaunchingWithOptions: launchOptions)
        }
        let channel = FlutterMethodChannel(name: "com.example.inyourskin", binaryMessenger: controller.binaryMessenger)
        channel.setMethodCallHandler { [weak self] call, result in
            guard let self = self else { return }
            switch call.method {
            case "yourTargetMethod":
                // 处理Native逻辑
                result("处理完成")
            default:
                result(FlutterMethodNotImplemented)
            }
        }
        GeneratedPluginRegistrant.register(with: self)
        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }
  }
  

• 用弱引用避免循环引用
  设置回调时使用[weak self]，防止旧实例无法释放，影响新实例创建。

通用注意事项 #

• Flutter端延迟调用Native方法
  不要在main函数里过早调用Native方法，确保引擎和Channel初始化完成后再执行，比如在initState中借助addPostFrameCallback延迟：

  final _channel = MethodChannel('com.example.inyourskin');
  
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      // 这里调用Native方法更安全
      _channel.invokeMethod('yourTargetMethod');
    });
  }
  

• Native后台任务先检查绑定状态
  如果后台有任务需要调用Flutter，Android端先判断flutterEngine.dartExecutor.isAttached，iOS端确认binaryMessenger有效，避免在未绑定状态下发消息。

内容的提问来源于stack exchange，提问作者Jalpa Panchal