Is there a way I can have my HookWidget rebuild when the text of the TextEditingController changes?

Question

I have a test edit field. When there is no text, I want a button disabled. When there is text in the TextField, I want the button enabled.

I am using flutter_hooks to reduce boiler plate code for controllers.

In the following example, when I enter test into the text field, the button never enables, because build is not triggered? How can I trigger a build when using a text editing controller with flutter hooks?

class MyHomePage extends HookWidget {
  const MyHomePage({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    var ctrl = useTextEditingController();
    VoidCallback? onPressed;
    if (ctrl.text.isNotEmpty) {
      onPressed = () => print("Pressed!");
    }
    return Scaffold(
      body: Column(
        children: [
          TextField(
            controller: ctrl,
          ),
          ElevatedButton(onPressed: onPressed, child: Text("Button")),
        ],
      )
    );
  }
}

Answer 1

You can Achieve this using useState and useTextEditingController

var istextchanged = useState<bool>(false);
ctrl.addListener(() {
  if (ctrl.text.isEmpty) {
    istextchanged.value = false;
  } else {
    istextchanged.value = true;
  }
});

Yourwidget

class MyHomePages2 extends HookWidget {
  const MyHomePages2({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    var ctrl = useTextEditingController();
    var istextchanged = useState<bool>(false);
    ctrl.addListener(() {
      if (ctrl.text.isEmpty) {
        istextchanged.value = false;
      } else {
        istextchanged.value = true;
      }
    });

    VoidCallback? onPressed = () {
      print("change");
    };
    if (ctrl.text.isNotEmpty) {
      onPressed = () => print("Pressed!");
    }
    return Scaffold(
        body: Column(
      children: [
        TextField(
          controller: ctrl,
          onChanged: (v) {},
        ),
        ElevatedButton(
            onPressed: istextchanged.value ? onPressed : null,
            child: Text("Button"))
      ],
    ));
  }
}

Package used flutter_hooks: ^0.18.2+1 pub.dev/flutter_hooks

SampleCode

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

int myvalue = 0;

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  @override
  void initState() {
    // functions().then((int value) {
    //   setState(() {
    //     myvalue = value;
    //   });
    // future is completed you can perform your task
    // });
  }

  Future<int> functions() async {
    // do something here
    return Future.value();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: MyHomePages2(),
    );
  }
}

class MyHomePages2 extends HookWidget {
  const MyHomePages2({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    var ctrl = useTextEditingController();
    var istextchanged = useState<bool>(false);
    ctrl.addListener(() {
      if (ctrl.text.isEmpty) {
        istextchanged.value = false;
      } else {
        istextchanged.value = true;
      }
    });

    VoidCallback? onPressed = () {
      print("change");
    };
    if (ctrl.text.isNotEmpty) {
      onPressed = () => print("Pressed!");
    }
    return Scaffold(
        body: Column(
      children: [
        TextField(
          controller: ctrl,
          onChanged: (v) {},
        ),
        ElevatedButton(
            onPressed: istextchanged.value ? onPressed : null,
            child: Text("Button"))
      ],
    ));
  }
}