Flutter how to trigger dialog when timer ends

You can copy paste run full code below
If 0 means AnimationStatus.completed, you can listen this event and pop up dialog

code snippet

controller =        AnimationController(duration: const Duration(seconds: 10), vsync: this);    controller.addStatusListener(((status) {      if (status == AnimationStatus.completed) {        print("completed");        _neverSatisfied();

demo

full code

import 'package:flutter/material.dart';void main() => runApp(MyApp());class MyApp extends StatelessWidget {  // This widget is the root of your application.  @override  Widget build(BuildContext context) {    return MaterialApp(      title: 'Flutter Demo',      theme: ThemeData(        // This is the theme of your application.        //        // Try running your application with "flutter run". You'll see the        // application has a blue toolbar. Then, without quitting the app, try        // changing the primarySwatch below to Colors.green and then invoke        // "hot reload" (press "r" in the console where you ran "flutter run",        // or simply save your changes to "hot reload" in a Flutter IDE).        // Notice that the counter didn't reset back to zero; the application        // is not restarted.        primarySwatch: Colors.blue,      ),      home: MyHomePage(title: 'Flutter Demo Home Page'),    );  }}class MyHomePage extends StatefulWidget {  MyHomePage({Key key, this.title}) : super(key: key);  // This widget is the home page of your application. It is stateful, meaning  // that it has a State object (defined below) that contains fields that affect  // how it looks.  // This class is the configuration for the state. It holds the values (in this  // case the title) provided by the parent (in this case the App widget) and  // used by the build method of the State. Fields in a Widget subclass are  // always marked "final".  final String title;  @override  _MyHomePageState createState() => _MyHomePageState();}class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {  int _counter = 0;  AnimationController controller;  void _incrementCounter() {    setState(() {      // This call to setState tells the Flutter framework that something has      // changed in this State, which causes it to rerun the build method below      // so that the display can reflect the updated values. If we changed      // _counter without calling setState(), then the build method would not be      // called again, and so nothing would appear to happen.      _counter++;    });  }  @override  void initState() {    // TODO: implement initState    super.initState();    controller =        AnimationController(duration: const Duration(seconds: 10), vsync: this);    controller.addStatusListener(((status) {      if (status == AnimationStatus.completed) {        print("completed");        _neverSatisfied();      } else if (status == AnimationStatus.dismissed) {        //controller.forward();      }    }));    controller.forward();  }  Future<void> _neverSatisfied() async {    return showDialog<void>(      context: context,      barrierDismissible: false, // user must tap button!      builder: (BuildContext context) {        return AlertDialog(          title: Text('Rewind and remember'),          content: SingleChildScrollView(            child: ListBody(              children: <Widget>[                Text('You will never be satisfied.'),                Text('You\’re like me. I’m never satisfied.'),              ],            ),          ),          actions: <Widget>[            FlatButton(              child: Text('Regret'),              onPressed: () {                Navigator.of(context).pop();              },            ),          ],        );      },    );  }  @override  Widget build(BuildContext context) {    // This method is rerun every time setState is called, for instance as done    // by the _incrementCounter method above.    //    // The Flutter framework has been optimized to make rerunning build methods    // fast, so that you can just rebuild anything that needs updating rather    // than having to individually change instances of widgets.    return Scaffold(      appBar: AppBar(        // Here we take the value from the MyHomePage object that was created by        // the App.build method, and use it to set our appbar title.        title: Text(widget.title),      ),      body: Center(        // Center is a layout widget. It takes a single child and positions it        // in the middle of the parent.        child: Column(          // Column is also a layout widget. It takes a list of children and          // arranges them vertically. By default, it sizes itself to fit its          // children horizontally, and tries to be as tall as its parent.          //          // Invoke "debug painting" (press "p" in the console, choose the          // "Toggle Debug Paint" action from the Flutter Inspector in Android          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)          // to see the wireframe for each widget.          //          // Column has various properties to control how it sizes itself and          // how it positions its children. Here we use mainAxisAlignment to          // center the children vertically; the main axis here is the vertical          // axis because Columns are vertical (the cross axis would be          // horizontal).          mainAxisAlignment: MainAxisAlignment.center,          children: <Widget>[            AnimatedBuilder(              animation: controller,              builder: (BuildContext context, Widget child) {                return controller.value == 0? Text("0") : Text("Run");              },            ),            Text(              'You have pushed the button this many times:',            ),            Text(              '$_counter',              style: Theme.of(context).textTheme.display1,            ),          ],        ),      ),      floatingActionButton: FloatingActionButton(        onPressed: _incrementCounter,        tooltip: 'Increment',        child: Icon(Icons.add),      ), // This trailing comma makes auto-formatting nicer for build methods.    );  }}

Try this :

  AnimatedBuilder(    animation: controller,      builder: (BuildContext context, Widget child) {                                    return controller.value == 0? autoSubmition() : Container();      },  ),//shows this error setState() or markneedsbuild() called during build error  autoSubmition() {    //model.setTestTimerRunning(false);    var autoResponse = {      "submitDialogTitle":          "You're have ran out of time. Please Submit your answer",      "submitDialogSubtitle":          "If you cancel this test will be terminated. Your score will be reset to zero"    };// Wrap showDialog inside the widgetsBinding    WidgetsBinding.instance            .addPostFrameCallback((_) => showDialog(      context: context,      barrierDismissible: false,      builder: (_) {        return AutoSubmitTestDialog(            context: context,            model: model,            testItem: testItem,            messages: autoResponse);      },    ));  }