Hello, I found a solution for my case:

create an appState \"timerStarted\"
create a Custom Widget \"TimerDispose\"
add TimerDispose in your page

timerStarted will be false when page is load / unload, and you can use this variable to stop your periodic action.

// Automatic FlutterFlow imports\nimport '/backend/backend.dart';\nimport '/backend/schema/structs/index.dart';\nimport '/backend/schema/enums/enums.dart';\nimport '/actions/actions.dart' as action_blocks;\nimport '/flutter_flow/flutter_flow_theme.dart';\nimport '/flutter_flow/flutter_flow_util.dart';\nimport '/custom_code/widgets/index.dart'; // Imports other custom widgets\nimport '/custom_code/actions/index.dart'; // Imports custom actions\nimport '/flutter_flow/custom_functions.dart'; // Imports custom functions\nimport 'package:flutter/material.dart';\n// Begin custom widget code\n// DO NOT REMOVE OR MODIFY THE CODE ABOVE!\n\nimport 'package:flutter/foundation.dart';\n\nimport 'index.dart'; // Imports other custom widgets\n\nclass TimerDispose extends StatefulWidget {\n  const TimerDispose({\n    super.key,\n    this.width,\n    this.height,\n  });\n\n  final double? width;\n  final double? height;\n\n  @override\n  State<TimerDispose> createState() => _TimerDisposeState();\n}\n\nclass _TimerDisposeState extends State<TimerDispose> {\n  @override\n  Widget build(BuildContext context) {\n    return Container();\n  }\n\n  @override\n  void initState() {\n    if (kDebugMode) {\n      print(\"--> initState TimerDispose\");\n    }\n    super.initState();\n    FFAppState().timerStarted = false;\n  }\n\n  @override\n  void dispose() {\n    if (kDebugMode) {\n      print(\"--> dispose TimerDispose\");\n    }\n    FFAppState().timerStarted = false;\n    super.dispose();\n  }\n}

How stop "periodic" when page is unloaded