如何在Flutter应用程序的initState期间使用提供者的数据

问题描述

我通过将Provider添加为状态管理来重构Flutter应用程序代码.

I am refactoring my Flutter application code by adding Provider as a state management.

所需的行为:打开主屏幕时，应用应检查用户是否已通过电子邮件验证，如果未通过验证，则应显示对话框弹出窗口.

Desired behavior: When Home screen opens, app should check if users email verified, if it's not then should show dialog popup.

问题:，当我通过构造函数传递EmailVerified数据时，它运行良好，但是如果我想使用Provider，则无法在 initState()处获得此数据代码>生命周期.

Problem: It worked fine when I was passing data for EmailVerified through the constructor, but if I want to use Provider, I can't get this data at initState() lifecycle.

您能为我推荐这种用例的正确方法吗?

Can you please recommend me correct approach for such use case?

import 'package:myapp/services/authentication.dart';
import 'package:myapp/screens/settings_screen.dart';
import 'package:flutter/material.dart';
import 'package:myapp/services/authentication.dart';
import 'package:provider/provider.dart';

class HomeScreen extends StatefulWidget {

  @override
  State<StatefulWidget> createState() => new _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  final GlobalKey<FormState> formKey = GlobalKey<FormState>();
  bool _isEmailVerified = false;

  @override
  void initState() {
    super.initState();
    _checkEmailVerification(); // <=== Method which should show Dialog box if email is not verified which is coming from "Auth" Provider
  }

  @override
  Widget build(BuildContext context) {
    final auth = Provider.of<Auth>(context, listen: false); // <==== Service from Provider, which contains data for _isEmailVerified
    auth.isEmailVerified().then((value) => _isEmailVerified = value);

    return new Scaffold(
      appBar: new AppBar(
        title: new Text('My App'),
      ),
      body: Center(
        child: Column(
          children: <Widget>[
            Text(
              'Welcome to my app',
            ),
          ],
        ),
      ),
    );
  }

  void _checkEmailVerification() async {
    _isEmailVerified = auth.isEmailVerified(); // <=== How can I use "auth" from Provider to get isEmailVerified data ????
    if (!_isEmailVerified) {
      _showVerifyEmailDialog();
    }
  }

  void _showVerifyEmailDialog() {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        // return object of type Dialog
        return AlertDialog(
          title: new Text("Verify your account"),
          content: new Text("Please verify account in the link sent to email"),
          actions: <Widget>[
            new FlatButton(
              child: new Text("Resend link"),
              onPressed: () {
                Navigator.of(context).pop();
                _resentVerifyEmail();
              },
            ),
            new FlatButton(
              child: new Text("Dismiss"),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
          ],
        );
      },
    );
  }

  void _resentVerifyEmail() {
    // Logic to send email
  }
}

推荐答案

您需要使用上下文来调用 Provider.of()，以便可以添加 addPostFrameCallback()在首次​​构建后即被调用，您可以在其中使用上下文

You need to use the context to call Provider.of() so you can add addPostFrameCallback() which is called after the first build, there you can use the context

@override
void initState() {
    super.initState();

    WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
      auth = Provider.of<Auth>(context, listen: false);
    });
}

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