错误警告 Image.asset(......) Flutter, Dart答案

【问题标题】：Error Warning Image.asset(......) Flutter, Dart错误警告 Image.asset(......) Flutter, Dart
【发布时间】：2021-01-23 16:27:44
【问题描述】：

我是 Flutter/Dart 编程的初学者，当我想将图像添加到我的应用程序时，我仍然总是在错误中运行。我想用小部件 Image.asset 来做这件事，实际上我认为我在 pubspec.yaml 中完成了所有设置，并在项目文件夹中创建了一个新文件夹 assets/images ，这样它就与 pubspec 处于同一级别.yaml。起初我遇到了一些错误，比如只有一个依赖项，或者它应该是一个字符串，所以我想我已经修复了它们，但从那以后我得到了以下错误警告：

代码 main.dart：

import 'dart:ui';
import 'package:flutter/widgets.dart';
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: AppBar(
              title: Text("TEST-TEST-TEST"), //Titel AppBar
              backgroundColor: Colors.redAccent, //Farbe AppBar
            ),
            body: Center(
                child: Column(children: [
              Text(
                'Hello World :)',
                style: TextStyle(
                    fontSize: 26,
                    fontWeight: FontWeight.bold,
                    color: Colors.blue[800]),
              ),
              Text(
                'Second Line - works ;)',
                style: TextStyle(
                    fontSize: 20,
                    fontWeight: FontWeight.normal,
                    color: Colors.blue[800]),
              ),
              Image.asset(
                'assets/images/pic_1.jpg'),
            ]))));
  }
}

enter code here

代码 pubspec.yaml：

name: hello_world

environment:
  # The pub client defaults to an <2.0.0 sdk constraint which we need to explicitly overwrite.
  sdk: ">=2.0.0-dev.68.0 <3.0.0"



dependencies:
  flutter:
   #sdk: flutter 
   assets:
     - assets/images/pic_1.jpg

  


  characters: 1.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  collection: 1.14.13 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  meta: 1.1.8 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  typed_data: 1.2.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  vector_math: 2.0.8 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"

dev_dependencies:
  flutter_driver:
    sdk: flutter
  flutter_test:
    sdk: flutter
  test: 1.15.2

  _fe_analyzer_shared: 5.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  analyzer: 0.39.12 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  archive: 2.0.13 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  args: 1.6.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  async: 2.4.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  boolean_selector: 2.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  charcode: 1.1.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  clock: 1.0.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  convert: 2.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  coverage: 0.14.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  crypto: 2.1.5 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  csslib: 0.16.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  fake_async: 1.1.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  file: 5.2.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  glob: 1.2.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  html: 0.14.0+3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  http: 0.12.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  http_multi_server: 2.2.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  http_parser: 3.1.4 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  intl: 0.16.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  io: 0.3.4 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  js: 0.6.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  json_rpc_2: 2.2.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  logging: 0.11.4 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  matcher: 0.12.8 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  mime: 0.9.6+3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  node_interop: 1.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  node_io: 1.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  node_preamble: 1.4.12 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  package_config: 1.9.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  path: 1.7.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  pedantic: 1.9.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  pool: 1.4.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  pub_semver: 1.4.4 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  shelf: 0.7.5 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  shelf_packages_handler: 2.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  shelf_static: 0.2.8 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  shelf_web_socket: 0.2.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  source_map_stack_trace: 2.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  source_maps: 0.10.9 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  source_span: 1.7.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  stack_trace: 1.9.5 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  stream_channel: 2.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  string_scanner: 1.0.5 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  sync_http: 0.2.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  term_glyph: 1.1.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  test_api: 0.2.17 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  test_core: 0.3.10 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  vm_service: 4.1.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  vm_service_client: 0.2.6+2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  watcher: 0.9.7+15 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  web_socket_channel: 1.1.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  webdriver: 2.1.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  webkit_inspection_protocol: 0.7.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
  yaml: 2.2.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"


# PUBSPEC CHECKSUM: f482

错误警告：

[examples/hello_world] flutter pub get 在 hello_world 中运行“flutter pub get”...
因为 hello_world 依赖于来自未知来源“资产”的颤振，所以版本求解失败。 pub get failed (1; 因为 hello_world 依赖于来自未知来源“资产”的颤振，版本解决失败。) 退出代码 1

【问题讨论】：

你尝试过 Flutter 升级吗？

标签： image flutter dart assets

【解决方案1】：

您的 pubspec.yaml 部分 sn-p（错误）

dependencies:
  flutter:
   #sdk: flutter 
   assets:
     - assets/images/pic_1.jpg

正确的方法：

#dependencies: //Remove this line
flutter:                       //And 
   #sdk: flutter               // indent
   assets:                     // this block 
     - assets/images/pic_1.jpg // back

当你想要声明 Flutter 资产时

【讨论】：

【解决方案2】：

在我看来，您的 pubspec.yaml 文件的结构并不完全正确。尝试在“flutter”部分下声明资产（您的资产似乎在“dependencies”部分下，这解释了错误消息因为 hello_world 依赖于来自未知来源“assets”的颤振）：

name: hello_world
description: A new Flutter application.

version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^0.1.2

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  uses-material-design: true
  assets:
    - assets/images/pic_1.jpg

【讨论】：