当 state 更改时，有状态小部件不重建子小部件（颤振）

Question

I'm building a form that signs up the user on Firebase, and where the ElevatedButton either displays "CREATE YOUR ACCOUNT" or a CircularProgressIndicator, based on the state of isLoading. Yet, the button's child doesn't change based on isLoading.

The states does change -- I'm printing out isLoading in the middle of my onPressed methode, and I do see it as true .

Why isn't the button changing its child?

import 'package:flutter/material.dart';
import 'package:tedy/components/custom_text_form_field.dart';
import 'package:tedy/components/custom_wrapper.dart';

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

  @override
  State<EmployerOnboardingOneView> createState() =>
      _EmployerOnboardingOneViewState();
}

class _EmployerOnboardingOneViewState extends State<EmployerOnboardingOneView> {
  var firstNameController = TextEditingController();
  var lastNameController = TextEditingController();
  var emailController = TextEditingController();
  var passwordController = TextEditingController();
  var passwordConfirmController = TextEditingController();

  bool isLoading = false;

  @override
  Widget build(BuildContext context) {
    var screenWidth = MediaQuery.of(context).size.width;

    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.white,
        centerTitle: true,
        title: SizedBox(
          height: 50,
          child: Image.asset(
            'assets/images/tedy_logo_color.png',
            filterQuality: FilterQuality.high,
          ),
        ),
      ),
      body: CustomWrapper(
        maxWidth: 400,
        children: [
          Text(
            'Create a Tedy account for your company',
            style: Theme.of(context).textTheme.headline3,
            textAlign: TextAlign.center,
          ),
          const SizedBox(
            height: 20,
          ),
          CustomTextFormField(
              controller: firstNameController, label: 'First Name'),
          const SizedBox(
            height: 20,
          ),
          CustomTextFormField(
              controller: lastNameController, label: 'Last Name'),
          const SizedBox(
            height: 20,
          ),
          CustomTextFormField(controller: emailController, label: 'Email'),
          const SizedBox(
            height: 20,
          ),
          CustomTextFormField(
              controller: passwordController,
              isPassword: true,
              label: 'Password'),
          const SizedBox(
            height: 20,
          ),
          CustomTextFormField(
              controller: passwordConfirmController,
              isPassword: true,
              label: 'Confirm your password'),
          const SizedBox(
            height: 20,
          ),
          SizedBox(
            width: double.infinity,
            height: 50,
            child: ElevatedButton(
              style: ElevatedButton.styleFrom(
                  primary: Theme.of(context).primaryColor),
              onPressed: () async {
                setState(() {
                  isLoading = true;
                });
                if (passwordController.text != passwordConfirmController.text) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(
                      content: Text('Passwords must match'),
                      backgroundColor: Colors.red,
                    ),
                  );
                } else {
                  try {
                    FirebaseAuth.instance
                        .createUserWithEmailAndPassword(
                            email: emailController.text,
                            password: passwordController.text)
                        .then((value) {
                      Navigator.pushNamedAndRemoveUntil(
                          context, '/', (route) => false);
                    });
                    print(isLoading);
                  } on FirebaseAuthException catch (e) {
                    ScaffoldMessenger.of(context).showSnackBar(
                      SnackBar(
                        content: Text(e.message != null
                            ? e.message as String
                            : 'There was an error.'),
                        backgroundColor: Colors.red,
                      ),
                    );
                  }
                }
                setState(() {
                  isLoading = false;
                });
              },
              child: isLoading
                  ? const SizedBox(
                      width: 30,
                      height: 30,
                      child: CircularProgressIndicator(
                        color: Colors.white,
                      ),
                    )
                  : const Text('CREATE YOUR ACCOUNT'),
            ),
          )
        ],
      ),
    );
  }
}

Answer 1

createUserWithEmailAndPassword is async, so you have to await it

await FirebaseAuth.instance
                        .createUserWithEmailAndPassword(
                            email: emailController.text,
                            password: passwordController.text);
Navigator.pushNamedAndRemoveUntil(
                          context, '/', (route) => false);

Your code set isLoading to true, does the password logic and calls this method. But since you don't await it here it just skips it and calls the setState with isLoading = false.

Answer 2

You are using then for the future. so the last isLoading = false; executed when you pressed the button. You can change state inside.then instead of end. Also you can add inside FirebaseAuthException . make sure to remove last isLoading = false;

FirebaseAuth.instance
    .createUserWithEmailAndPassword(
        email: emailController.text,
        password: passwordController.text)
    .then((value) {
  setState(() {
    isLoading = false;
  });
  Navigator.pushNamedAndRemoveUntil(
      context, '/', (route) => false);
});