const 列表文字中的值必须是常量，在 Flutter 中将图像添加到列小部件时出现此错误

Question

为什么我无法在此处添加图片？在 Flutter 中将图像添加到列小部件时出现此错误。当我删除 new 关键字时，我收到另一个错误。请检查这个问题。我创建了一个名为 assets>images>girl-icon.jpg 的文件夹。另外，我启用了 pubspec.yaml 文件中的资产。

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'My First Flutter App',
        theme: ThemeData(
          scaffoldBackgroundColor: Colors.white,
        ),
        home: const WelcomeScreen());
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('First Page'),
        backgroundColor: Colors.amber,
      ),
      body:Center(

      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: const <Widget> [

          Text("Login",
              style: TextStyle(
              fontSize: 30,
              fontWeight: FontWeight.bold,
              )),
          new Image.asset("assets/images/girl-icon.jpg"),
        ],
        ),
        heightFactor: 30,

      ),
      );
    }}

See screenshot of the problem here

Answer 1

const 需要硬编码的 constant 值，并且您在构建 dynamically 时将 MyApp 称为常量，这就是它抛出错误的原因。在 MyApp 之前删除 const 以解决此问题：

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

还有从这里：

children: <Widget> [

          Text("Login",
              style: TextStyle(
              fontSize: 30,
              fontWeight: FontWeight.bold,
              )),
          new Image.asset("assets/images/girl-icon.jpg"),
        ]

Answer 2

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'My First Flutter App',
        theme: ThemeData(
          scaffoldBackgroundColor: Colors.white,
        ),
        home: const WelcomeScreen());
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('First Page'),
        backgroundColor: Colors.amber,
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text("Login",
                style: TextStyle(
                  fontSize: 30,
                  fontWeight: FontWeight.bold,
                )),
            Image.asset("assets/images/girl-icon.jpg"),
          ],
        ),
        heightFactor: 30,
      ),
    );
  }
}

我的方法就是删除

const <Widget>