小编Nir*_*mar的帖子

我正在制作一个基本的购物应用程序。我的想法是制作我的产品的列表图块，以便我可以编辑或删除产品。因此，当我导航到该页面时，它显示了一个空白的白色页面，并出现如图所示的错误 空白屏幕 错误

import 'package:flutter/material.dart';

class UserProductItem extends StatelessWidget {
  final String title;
  final String imageUrl;
  UserProductItem(this.title, this.imageUrl);

  @override
  Widget build(BuildContext context) {
    return ListTile(
      title: Text(title),
      leading: CircleAvatar(
        backgroundImage: NetworkImage(imageUrl),
      ),
      trailing: Row(
        children: [
          IconButton(
            icon: Icon(Icons.edit),
            onPressed: () {},
            color: Theme.of(context).primaryColor,
          ),
          IconButton(
            icon: Icon(Icons.delete),
            onPressed: () {},
            color: Theme.of(context).errorColor,
          )
        ],
      ),
    );
  }
}

该程序中有 2 个错误，如上图所示

Main.dart 文件

void main() {
 
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Personal Expenses ',
      theme: ThemeData(
        primarySwatch: Colors.green,
        accentColor: Colors.amber,
        //errorColor: Colors.red[700],
        fontFamily: 'Quicksand',
        textTheme: ThemeData.light().textTheme.copyWith(
            title: TextStyle(
              fontFamily: 'OpenSans',
              fontWeight: FontWeight.bold,
              fontSize: 18,
            ),
            button: TextStyle(color: Colors.amber)),
        appBarTheme: AppBarTheme(
          textTheme: ThemeData.light().textTheme.copyWith(
                title: TextStyle(
                  fontFamily: 'OpenSans',
                  fontSize: 20,
                  fontWeight: FontWeight.bold,
                ),
              ),
        ),
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
 
  @override
  _MyHomePageState createState() => …

这些是我得到的错误

这是我的 chart.dart 文件

import 'package:flutter/material.dart';
import 'package:udemy_expenses_app/widgets/chart_bar.dart';
import '../models/tanscations.dart';
import 'package:intl/intl.dart';
import './chart_bar.dart';

class Chart extends StatelessWidget {
  final List<Transaction> recentTransactions;
  Chart(this.recentTransactions);
  List<Map<String, Object>> get groupedTransactionValues {
  return List.generate(7, (index) {
   final weekDay = DateTime.now().subtract(
    Duration(
      days: index,
    ),
  );
  double totalSum = 0.0;
  for (var i = 0; i < recentTransactions.length; i++) {
    if (recentTransactions[i].date.day == weekDay.day &&
        recentTransactions[i].date.month == weekDay.month &&
        recentTransactions[i].date.year == weekDay.year) {
      totalSum += recentTransactions[i].amount;
    }
  }

  return {
    'day': DateFormat.E().format(weekDay).substring(0, 1),
    'amount': totalSum, …