未處理的異常：MissingPluginException（在通道插件上找不到方法 X 的實現。flutter.io/Y）

Question

我已按照此處的步驟將我的 flutter 項目遷移到 null 安全。

從那時起，我時不時地在以下多個軟件包中遇到此錯誤。

Unhandled Exception: MissingPluginException(No implementation found for method getAll on channel plugins.flutter.io/shared_preferences)

以上是shared_preferences ，但path_provider和firebase_analytics會拋出類似的錯誤。

這是我的pubspec.yaml

name: news_app
description: A news app

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.10+22

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  curved_navigation_bar: ^1.0.1
  http: ^0.13.4
  webview_flutter: ^2.8.0
  firebase_core: ^1.10.6
  firebase_auth: ^3.3.4
  flutter_cache_manager: ^3.3.0
  flutter_widget_from_html_core: ^0.8.4
  flutter_widget_from_html: ^0.8.0
  flutter_html: ^2.1.5
  page_view_indicators: ^2.0.0
  splashscreen: ^1.3.5
  intl: ^0.17.0
  jiffy: ^5.0.0
  dio: ^4.0.4
  dio_http_cache: ^0.3.0
  shared_preferences: ^2.0.6
  connectivity: ^3.0.6
  share: ^2.0.4
  sqflite: ^2.0.1
  path_provider: ^2.0.2
  timeago: ^3.1.0
  auto_size_text: ^3.0.0
  flutter_tts: ^3.3.2
  firebase_messaging: ^11.2.4
  firebase_analytics: ^9.0.4
  flutter_local_notifications: ^9.1.5
  chewie: ^1.2.2
  flutter_svg: ^0.22.0
  provider: ^5.0.0
  webview_flutter_plus: ^0.2.3+1
  firebase_admob: ^0.11.2
  scroll_app_bar: ^2.0.0
  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^1.0.4

dev_dependencies:
  flutter_test:
    sdk: flutter

  flutter_launcher_icons: ^0.9.2

flutter_icons:
  image_path: "assets/logo.jpg"
  android: true
  ios: true

# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:
  fonts:
    - family: sourcePro
      fonts:
        - asset: assets/SourceSansPro-Light.ttf
    - family: serifPro
      fonts:
        - asset: assets/SourceSerifPro-Light.otf
    - family: metaSerifPro
      fonts:
        - asset: assets/FFMetaSerifPro-Light.ttf
  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true
  assets:
    - assets/logo.jpeg
    - assets/tbs_logo_transparent.png
    - assets/logo.png
    - assets/logo.jpg
  # To add assets to your application, add an assets section, like this:
  # assets:
  #  - images/a_dot_burr.jpeg
  #  - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.dev/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.dev/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # fonts:
  #   - family: Schyler
  #     fonts:
  #       - asset: fonts/Schyler-Regular.ttf
  #       - asset: fonts/Schyler-Italic.ttf
  #         style: italic
  #   - family: Trajan Pro
  #     fonts:
  #       - asset: fonts/TrajanPro.ttf
  #       - asset: fonts/TrajanPro_Bold.ttf
  #         weight: 700
  #
  # For details regarding fonts from package dependencies,
  # see https://flutter.dev/custom-fonts/#from-packages

這是flutter doctor的結果

[✓] Flutter (Channel stable, 2.5.3, on Ubuntu 16.04.7 LTS 4.15.0-142-generic, locale en_US.UTF-8)
[✓] Android toolchain - develop for Android devices (Android SDK version 31.0.0)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2020.3)
[✓] VS Code (version 1.63.2)
[✓] Connected device (3 available)

我嘗試了從其他帖子中發現的以下措施，以及 github 問題。

1. 我嘗試切換到不同flutter頻道。
2. 還嘗試更改上述軟件包的版本。
3. 嘗試使用flutter clean刪除緩存。
4. 我卸載了應用程序並重新安裝了它，仍然一樣。
5. 重新安裝了所有軟件包。
6. 使緩存無效后重新啟動 Android Studio。

它沒有任何工作。 在遷移到 null 之前，安全工作正常。

Answer 1

我可以建議你換一種方式。 不要將現有項目遷移到 null 安全性，而是創建新項目（具有 null 安全性）並從舊項目復制lib文件夾。 然后將您從舊的pubspec.yaml文件安裝到新的pubspec.yaml文件中添加軟件包（確保您擁有最新版本。）。 （以及資產和 fonts，如果有）。 如果您添加的軟件包需要針對 iOS 和 Android 平台進行額外集成，請執行此操作。 我以這種方式更新舊版本的 lutter（即非空安全）項目。