小编del*_*ram的帖子

大家好，这是我的整个方法：

Future<void> init() async {
    FirebaseAuth.instance.userChanges().listen((user) {
      if (user != null) {
        _loginState = ApplicationLoginState.loggedIn;
        _guestBookSubscription = FirebaseFirestore.instance
            .collection('guestbook')
            .orderBy('timestamp', descending: true)
            .limit(3)
            .snapshots()
            .listen((snapshot) {
          _guestBookMessages = [];
          snapshot.docs.forEach((document) {
            _guestBookMessages.add(
              GuestBookMessage(
                name: document.data()['name'] as String,
                message: document.data()['text'] as String,
              ),
            );
          });
          notifyListeners();
        });
      } else {
        _loginState = ApplicationLoginState.loggedOut;
        _guestBookMessages = [];
        _guestBookSubscription?.cancel();
      }
      notifyListeners();
    });
  }

dart 抱怨的部分是：

snapshot.docs.forEach((document) {
            _guestBookMessages.add(
              GuestBookMessage(
                name: document.data()['name'] as String,
                message: document.data()['text'] as String,
              ),
            );
          });

我怎样才能改变这个方法而不破坏整个功能？我只是在寻找一种让 dart 快乐的方法。我提前感谢您的帮助。

 
import 'package:flutter/material.dart';

class SignInPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Time Tracker'),
        elevation: 5.0,
      ),
      body: _buildContent(),
      backgroundColor: Colors.amber[50],
    );
  }

  Widget _buildContent() {
    return Padding(
      padding: EdgeInsets.all(16.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          Text(
            'Sing in',
            textAlign: TextAlign.center,
            style: TextStyle(
              fontSize: 32.0,
              fontWeight: FontWeight.w600,
            ),
          ),
          SizedBox(height: 8.0),
          ElevatedButton(
            child: Text('Sing in with google'),
            onPressed: () {},
            style: ElevatedButton.styleFrom(
                primary: Colors.purple[200],
                onPrimary: Colors.black87,
                elevation: 6.0,
                shadowColor: Colors.yellow[200],
          ),
        ],
      ), …

问题是标题。我正在尝试构建 todoye 应用程序，正如您所看到的，回调被认为是 ValueChanged<bool?> 不是一个简单的函数，所以我无法将我的逻辑移动到另一个 statefullwidget 以减少我的应用程序中的重建，我尝试了不同的事情，但我得到了总是出错请帮忙。这是我的代码：

import 'package:flutter/material.dart';

class TaskTile extends StatefulWidget {
  @override
  _TaskTileState createState() => _TaskTileState();
}

class _TaskTileState extends State<TaskTile> {
  bool isChecked = false;
  void checkBoxCallBack(bool checkBoxState) {
    setState(() {
      isChecked = checkBoxState;
    });
  }

  @override
  Widget build(BuildContext context) {
    return ListTile(
      title: Text(
        'finish up angla\'s course today',
        style: TextStyle(
          decoration: isChecked ? TextDecoration.lineThrough : null,
        ),
      ),
      trailing: TaskCheckBox(
        checkBoxState: isChecked,
        toggleCheckBoxState: checkBoxCallBack,
      ),
    );
  }
}

class TaskCheckBox extends StatelessWidget {
  final …

大家好，第一个错误在标题中，让我先展示代码：

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:todoye_app_angela/models/task_data.dart';

class AddTaskScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    String newTaskTitle;
    return Container(
      color: Color(0xFF757575),
      child: Container(
        padding: EdgeInsets.all(20),
        decoration: BoxDecoration(
          color: Colors.limeAccent[400],
          borderRadius: BorderRadius.only(
            topLeft: Radius.circular(60),
            topRight: Radius.circular(60),
          ),
        ),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Text(
              'Add Task',
              textAlign: TextAlign.center,
              style: TextStyle(fontSize: 30, color: Colors.brown[900]),
            ),
            SizedBox(
              height: 12,
            ),
            TextField(
              onChanged: (newText) {
                newTaskTitle = newText;
              },
              autocorrect: false,
              decoration: InputDecoration(
                enabledBorder: OutlineInputBorder(
                  borderSide: BorderSide(
                    color: Colors.brown[800]!, …

实际的问题是我无法运行这个命令：firebase deploy --only firestore:indexes 正如您从这个链接中看到的： https: //codelabs.developers.google.com/codelabs/Friendlyeats-flutter/#12 我正在尝试通过我的 flutter 项目学习 firebase ..一般来说，我不理解这里的索引问题，如果您这样做，我将非常感谢您的努力...我添加了一个新终端，但仍然收到此错误...请帮我解决这个问题。