使用Flutter WindowManager禁用截图后，如何检测截图触发事件？

你已经通过FlutterWindowManager设置FLAG_SECURE禁用了截图，但该标记仅能阻止系统保存有效截图内容，无法直接捕获用户的截图操作。要实现检测截图尝试并提示用户，需要针对Android和iOS分别做原生层的监听，再通过MethodChannel通知Flutter端触发提示：

Android 端实现 #

Android系统在用户触发截图时会发送android.intent.action.SCREENSHOT广播，我们可以通过广播接收器监听该事件：

1. 编写Android原生广播接收器代码：

// MainActivity.kt
class ScreenshotReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        if (intent?.action == "android.intent.action.SCREENSHOT") {
            MethodChannel(flutterEngine?.dartExecutor?.binaryMessenger, "screenshot_channel")
                .invokeMethod("onScreenshotAttempt", null)
        }
    }
}

2. 在MainActivity中注册/注销广播接收器：

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val filter = IntentFilter("android.intent.action.SCREENSHOT")
    registerReceiver(ScreenshotReceiver(), filter)
}

override fun onDestroy() {
    super.onDestroy()
    unregisterReceiver(ScreenshotReceiver())
}

3. Flutter端监听回调并显示提示：

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

class SecureScreen extends StatefulWidget {
  @override
  _SecureScreenState createState() => _SecureScreenState();
}

class _SecureScreenState extends State<SecureScreen> {
  static const MethodChannel _channel = MethodChannel('screenshot_channel');
  bool secureMode = false;

  @override
  void initState() {
    super.initState();
    _initSecureMode();
    _listenScreenshotAttempt();
  }

  Future<void> _initSecureMode() async {
    await FlutterWindowManager.addFlags(FlutterWindowManager.FLAG_SECURE);
    setState(() {
      secureMode = true;
    });
  }

  void _listenScreenshotAttempt() {
    _channel.setMethodCallHandler((call) async {
      if (call.method == 'onScreenshotAttempt') {
        // 用Snackbar提示用户
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(
            content: Text('本应用已禁用截图功能'),
            duration: Duration(seconds: 2),
          ),
        );
        // 若要使用Toast，可引入fluttertoast包后替换为：
        // Fluttertoast.showToast(msg: '本应用已禁用截图功能');
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      // 你的页面布局内容
    );
  }
}

iOS 端实现 #

iOS没有截图动作的直接回调，但可以监听系统的UIApplicationUserDidTakeScreenshotNotification通知：

1. 编写iOS原生监听代码：

// AppDelegate.swift
override func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(onScreenshotTaken),
        name: UIApplication.userDidTakeScreenshotNotification,
        object: nil
    )
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
}

@objc func onScreenshotTaken() {
    let channel = FlutterMethodChannel(name: "screenshot_channel", binaryMessenger: window?.rootViewController as! FlutterBinaryMessenger)
    channel.invokeMethod("onScreenshotAttempt", arguments: nil)
}

2. Flutter端的监听和提示逻辑与Android端完全一致，直接复用上述代码即可。

注意事项 #

• Android的SCREENSHOT广播并非所有厂商都支持，部分定制ROM可能不会发送该广播，需做兼容性测试。
• iOS的通知会在截图完成后触发，此时截图已生成但内容为空，提示可告知用户截图无效。

内容的提问来源于stack exchange，提问作者Scodes