Question 80048 in Flutter Question posted in
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The method 'useEffect' isn't defined for the type – Flutter

I’m new to flutter and I want to implement the useEffect hook.

Here is my widget:

import 'dart:developer';

import 'package:flutter/material.dart';

class MarketRunnerChart extends StatefulWidget {
  const MarketRunnerChart({Key? key}) : super(key: key);

  @override
  State<MarketRunnerChart> createState() => _MarketRunnerChartState();
}

class _MarketRunnerChartState extends State<MarketRunnerChart> {
  @override
  Widget build(BuildContext context) {
    useEffect(() {
      log('okok');
    }, []);

    return Text("Some text");
  }
}

But I got the error The method 'useEffect' isn't defined for the type '_MarketRunnerChartState'.
enter image description here
When I remove the useEffect hook out of the build function and put it directly in the class I got error 'useEffect' must have a method body because '_MarketRunnerChartState' isn't abstract.
enter image description here
I’m used to work with React, but right now with flutter I can’t figure out how to implement that hook.

How am I supposed to do this ?

Tags:

3

Answers


  1. 0

    try add

    import 'package:flutter_hooks/flutter_hooks.dart';

    on top of your class file

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  2. 0

    import flutter hooks

    import 'package:flutter_hooks/flutter_hooks.dart';

class MarketRunnerChart extends StatefulWidget {
    const MarketRunnerChart({Key? key}) : super(key: key);

    @override
    State<MarketRunnerChart> createState() => _MarketRunnerChartState();
}

class _MarketRunnerChartState extends State<MarketRunnerChart> {
    useEffect(() {
        print('your log');
    }, []);

    @override
    Widget build(BuildContext context) {

        return Text("Some text");
    }
}
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  3. 0

    You can follow the doc example, import flutter_hooks, extend the HookWidget.

    import 'package:flutter_hooks/flutter_hooks.dart';

class Example extends HookWidget {
  const Example({Key? key, })
      : super(key: key);

  @override
  Widget build(BuildContext context) {
     //your variable/instance like to listen
    useEffect(() {
      log('okok');
    }, [...listenThisInstance...]);
    return Container();
  }
}

    More about useEffect

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