Thanks for reading my question.

I wonder why

Unhandled Exception: setState() called after dispose():_PomodoroState#42b6e(lifecycle state: defunct, not mounted)

is occured when I leave that page without pausing my timer function!

and also I want to know if it's fine to leave it like this.

But I think it's not good idea so I want some advices from you guys

This is my timer code.

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:cat_app/provider/counts.dart';

class Pomodoro extends StatefulWidget {
  @override
  _PomodoroState createState() => _PomodoroState();
}

class _PomodoroState extends State<Pomodoro> {
  double coinCount = 0;
  Stopwatch watch = Stopwatch();
  late Timer timer;
  bool startStop = true;

  String elapsedTime = '';

  updateTime(Timer timer) {
    if (watch.isRunning) {
      setState(() {
        print("startstop Inside=$startStop");
        elapsedTime = transformMilliSeconds(watch.elapsedMilliseconds);
      });
      if (coinCount == 360000) {
        context.read<Counts>().add(1);
        coinCount = 0;
      } else {
        coinCount = coinCount   10;
      }
      context.read<Times>().timeAdd(100);
    }
  }

  restartTimer() {
    updateTime(timer).cancel();
    setState(() {
      startStop = true;
      watch.stop();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      appBar: AppBar(
        elevation: 0,
        backgroundColor: Colors.white,
        leading: IconButton(
          icon: Icon(Icons.arrow_back, color: Colors.black),
          onPressed: () => Navigator.of(context).pop(),
        ),
      ),
      body: Container(
        padding: EdgeInsets.all(20.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(elapsedTime,
                style: TextStyle(fontFamily: 'Kitto', fontSize: 25.0)),
            SizedBox(height: 20.0),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                IconButton(
                  splashColor: Colors.transparent,
                  highlightColor: Colors.transparent,
                  onPressed: () => startOrStop(),
                  icon: Image.asset('assets/button.png'),
                  iconSize: 50,
                )
              ],
            )
          ],
        ),
      ),
    );
  }

  startOrStop() {
    if (startStop) {
      startWatch();
    } else {
      stopWatch();
    }
  }

  startWatch() {
    setState(() {
      startStop = false;
      watch.start();
      timer = Timer.periodic(Duration(milliseconds: 100), updateTime);
    });
  }

  stopWatch() {
    setState(() {
      startStop = true;
      watch.stop();
      setTime();
    });
  }

  setTime() {
    var timeSoFar = watch.elapsedMilliseconds;
    setState(() {
      elapsedTime = transformMilliSeconds(timeSoFar);
    });
  }

  transformMilliSeconds(int milliseconds) {
    int hundreds = (milliseconds / 10).truncate();
    int seconds = (hundreds / 100).truncate();
    int minutes = (seconds / 60).truncate();
    int hours = (minutes / 60).truncate();

    String hoursStr = (hours % 60).toString().padLeft(2, '0');
    String minutesStr = (minutes % 60).toString().padLeft(2, '0');
    String secondsStr = (seconds % 60).toString().padLeft(2, '0');

    return "$hoursStr:$minutesStr:$secondsStr";
  }
}

Can you tell me what is wrong?? I want to handle it!

CodePudding user response：

dispose() is used to execute code when the screen is disposed. Equal to onDestroy() of Android.

Example:

@override
void dispose() {
  anyController?.dispose();
  timer.cancel();
  super.dispose();
}

Add this in your Code