Flutter 使用json 文件生成dart 类文件报错：Target of URI doesn't exist Try creating the file referenced

参考：Flutter报错Target of URI hasn't been generated: - 简书 (jianshu.com)

首先需要确保你的项目根目录下的/jsons文件夹下：

ls .


    Directory: C:\Users\Administrator\Documents\Flutter\项目根目录


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----        2024-01-15   1:50 PM                .dart_tool
d-----        2024-01-15   1:23 PM                .idea
d-----        2024-01-15   1:25 PM                android
d-----        2024-01-15   1:23 PM                ios
d-----        2024-01-15   1:34 PM                jsons
d-----        2024-01-15   1:26 PM                lib
d-----        2024-01-15   1:23 PM                linux
d-----        2024-01-15   1:23 PM                macos
d-----        2024-01-15   1:23 PM                test
d-----        2024-01-15   1:23 PM                web
d-----        2024-01-15   1:23 PM                windows
-a----        2024-01-15   1:23 PM            745 .gitignore
-a----        2024-01-15   1:23 PM           1668 .metadata
-a----        2024-01-15   1:23 PM           1482 analysis_options.yaml
-a----        2024-01-15   1:50 PM          16112 pubspec.lock
-a----        2024-01-15   1:50 PM           4077 pubspec.yaml
-a----        2024-01-15   1:23 PM            581 README.md

是否有对应的结构无误的.json 文件，我这里以user.json 为例，其中是定义要生成的User 实体类的字段：

{
    "login": "TheFairyTale", 
    "avatar_url": "https://github.com/images/error/TheFairyTale.gif", 
    "type": "User", 
    "name?": "TheFairyTale", 
    "company?": "", 
    "blog?": "https://github.com/TheFairyTale", 
    "location?": "",
    "email?": "TheFairyTale@github.com", 
    "hireable?": false,
    "bio?": "", 
    "public_repos": 20, 
    "followers": 1, 
    "following": 0, 
    "created_at": "1970-01-01T00:00:00Z", 
    "updated_at": "1970-01-01T00:00:00Z", 
    "total_private_repos": 0, 
    "owned_private_repos": 0
  }

如果确定以上文件与内容无误，则需要引入以下依赖：

dependencies:
  flutter:
  json_model: ^1.0.0

先使用命令来根据项目根目录下的jsons 文件夹生成对应lib/models 下的dart 类文件：

flutter packages pub run json_model

此时在你的项目目录下的/lib/models 文件夹下就已经有了根据/jsons 文件夹内.json文件描述所生成的类文件了：

ls .\lib\models\


    Directory: C:\Users\Administrator\Documents\Flutter\项目根目录\lib\models


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a----        2024-01-15   2:01 PM            363 cacheConfig.dart
-a----        2024-01-15   1:47 PM             98 index.dart
-a----        2024-01-15   1:47 PM            431 profile.dart
-a----        2024-01-15   1:47 PM            721 repo.dart
-a----        2024-01-15   1:47 PM            629 user.dart

而如果你查看/lib/models 中生成的类文件，你会发现以下代码会报错，提示是

Target of URI doesn't exist: 'package:know_github_client_app/models/cacheConfig.g.dart.p'.

Try creating the file referenced by the URI, or try using a URI for a file that does exist.

part 'cacheConfig.g.dart';

这是因为在/lib/models 也就是类文件的同级目录下没有这个g.dart 文件，我们还需要添加以下依赖到pubspec.yml中：

dependencies:
  json_annotation: ^4.8.1

dev_dependencies:
  json_serializable: ^6.7.1
  build_runner: ^2.4.8

再使用以下命令以根据类文件生成对应的g.dart文件：

flutter packages pub run build_runner build

完整代码与命令：

pubspec.yml:

environment:
  sdk: '>=3.0.5 <4.0.0'

dependencies:
  flutter:
    sdk: flutter

  cupertino_icons: ^1.0.2
  json_annotation: ^4.8.1
  json_model: ^1.0.0

dev_dependencies:
  flutter_test:
    sdk: flutter

  flutter_lints: ^2.0.0
  json_serializable: ^6.7.1
  build_runner: ^2.4.8

第一步生成dart class 类文件命令:

flutter packages pub run json_model

第二步根据/lib/models 中的类文件生成对应的".g.class" 文件命令:

flutter packages pub run build_runner build