Flutter:无法创建插件包

Question

我正在尝试创建一个插件包，以便在 Android(使用 Kotlin)和 iOS(使用 Swift)中访问一些特定的硬件 API。为此，我尝试按照此处的说明进行操作:

https://flutter.dev/docs/development/packages-and-plugins/developing-packages

我现在只处理问题的 Swift 方面，所以到目前为止所做的工作如下:

1) 转到其他 Dart 包所在的目录(非 Flutter 包，并且运行良好)并运行:

flutter create --org com.example --template=plugin my_plugin

这创建了文档中描述的整个事情，并且没有报告错误。

2) 然后，如上一个链接所述，我前往 my_plugin/example 并运行 flutter build ios --no-codesign，具有以下(显然可以？)输出:

 Warning: Building for device with codesigning disabled. You will have to manually codesign before deploying to device.
 Building com.example.myPluginExample for device (ios-release)...
 Running pod install...                                              6.5s
 ├─Building Dart code...                                     2.9s
 ├─Generating dSYM file...                                   1.0s
 ├─Stripping debug symbols...                                0.6s
 ├─Assembling Flutter resources...                           1.0s
 └─Compiling, linking and signing...                         9.0s
 Xcode build done.                                           19.8s

3) 所以现在使用刚刚创建的插件，尝试将其添加到主项目中，因此，在其 pubspec.yaml 文件中，插入以下行(对于我正在使用的 Flutter 应用程序，该插件位于 ../pkgs 中:

dependencies:
  flutter:
    sdk: flutter
  my_plugin:
    path: ../pkgs/my_plugin

4)现在刚尝试在物理设备和模拟器中运行Flutter应用，总是出现如下错误:

Launching lib/main.dart on iPhone Xʀ in debug mode...
CocoaPods' output:
↳
      Preparing
    Analyzing dependencies
    Inspecting targets to integrate
      Using `ARCHS` setting to build architectures of target `Pods-Runner`: (``)
    Finding Podfile changes
      A my_plugin
      - Flutter
    Fetching external sources
    -> Fetching podspec for `Flutter` from `.symlinks/flutter/ios`
    -> Fetching podspec for `my_plugin` from `.symlinks/plugins/my_plugin/ios`
    Resolving dependencies of `Podfile`
    Comparing resolved specification to the sandbox manifest
      A Flutter
      A my_plugin
    Downloading dependencies
    -> Installing Flutter (1.0.0)
    -> Installing my_plugin (0.0.1)
      - Running pre install hooks
    [!] Unable to determine Swift version for the following pods:
    - `my_plugin` does not specify a Swift version and none of the targets (`Runner`) integrating it have the `SWIFT_VERSION` attribute set. Please contact the author or set the `SWIFT_VERSION` attribute in at least one of the targets that integrate this pod.
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/cocoapods-1.6.1/lib/cocoapods/installer/xcode/target_validator.rb:115:in `verify_swift_pods_swift_version'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/cocoapods-1.6.1/lib/cocoapods/installer/xcode/target_validator.rb:37:in `validate!'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/cocoapods-1.6.1/lib/cocoapods/installer.rb:459:in `validate_targets'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/cocoapods-1.6.1/lib/cocoapods/installer.rb:138:in `install!'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/cocoapods-1.6.1/lib/cocoapods/command/install.rb:48:in `run'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/claide-1.0.2/lib/claide/command.rb:334:in `run'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/cocoapods-1.6.1/lib/cocoapods/command.rb:52:in `run'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/gems/cocoapods-1.6.1/bin/pod:55:in `<top (required)>'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/bin/pod:22:in `load'
    /usr/local/Cellar/cocoapods/1.6.1/libexec/bin/pod:22:in `<main>'
Error output from CocoaPods:
↳
        WARNING: CocoaPods requires your terminal to be using UTF-8 encoding.
        Consider adding the following to ~/.profile:
        export LANG=en_US.UTF-8

Error running pod install
Error launching application on iPhone Xʀ.
Exited (sigterm)

5) 我试图通过将以下行添加到我可以在整个目录结构中看到的仅有的 2 个 Podfile 文件(属于应用程序和属于新插件“示例”的应用程序 - 这两个文件都是由 Flutter 的工具自动创建的，直到今天都没有收到任何编辑 -):

config.build_settings['SWIFT_VERSION'] = '4.1'

(这个想法来自 https://stackoverflow.com/a/52194702/6348097，是的:我尝试了至少一个不同的版本号)。错误还是一样。

生成的插件的 Podfile 是:

platform :ios, '9.0'

# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
ENV['COCOAPODS_DISABLE_STATS'] = 'true'

project 'Runner', {
  'Debug' => :debug,
  'Profile' => :release,
  'Release' => :release,
}

def parse_KV_file(file, separator='=')
  file_abs_path = File.expand_path(file)
  if !File.exists? file_abs_path
    return [];
  end
  pods_ary = []
  skip_line_start_symbols = ["#", "/"]
  File.foreach(file_abs_path) { |line|
      next if skip_line_start_symbols.any? { |symbol| line =~ /^\s*#{symbol}/ }
      plugin = line.split(pattern=separator)
      if plugin.length == 2
        podname = plugin[0].strip()
        path = plugin[1].strip()
        podpath = File.expand_path("#{path}", file_abs_path)
        pods_ary.push({:name => podname, :path => podpath});
      else
        puts "Invalid plugin specification: #{line}"
      end
  }
  return pods_ary
end

target 'Runner' do
  use_frameworks!

  # Prepare symlinks folder. We use symlinks to avoid having Podfile.lock
  # referring to absolute paths on developers' machines.
  system('rm -rf .symlinks')
  system('mkdir -p .symlinks/plugins')

  # Flutter Pods
  generated_xcode_build_settings = parse_KV_file('./Flutter/Generated.xcconfig')
  if generated_xcode_build_settings.empty?
    puts "Generated.xcconfig must exist. If you're running pod install manually, make sure flutter packages get is executed first."
  end
  generated_xcode_build_settings.map { |p|
    if p[:name] == 'FLUTTER_FRAMEWORK_DIR'
      symlink = File.join('.symlinks', 'flutter')
      File.symlink(File.dirname(p[:path]), symlink)
      pod 'Flutter', :path => File.join(symlink, File.basename(p[:path]))
    end
  }

  # Plugin Pods
  plugin_pods = parse_KV_file('../.flutter-plugins')
  plugin_pods.map { |p|
    symlink = File.join('.symlinks', 'plugins', p[:name])
    File.symlink(p[:path], symlink)
    pod p[:name], :path => File.join(symlink, 'ios')
  }
end

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      config.build_settings['SWIFT_VERSION'] = '4.1'
      config.build_settings['ENABLE_BITCODE'] = 'NO'
    end
  end
end

我在 Flutter 应用的 Podfile 中添加了相同的内容。此外，指定 iOS 平台的第一行最初是注释的(这会产生警告)，所以我还取消了两个 podfile 中的该行的注释。

这是flutter doctor的输出:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.2.1, on Mac OS X 10.14.3 18D109, locale en-ES)
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
[✓] iOS toolchain - develop for iOS devices (Xcode 10.2)
[✓] Android Studio (version 3.3)
[✓] VS Code (version 1.33.1)
[✓] Connected device (1 available)

• No issues found!

问题只是如何使这项工作。我什至没有开始添加自己的代码，但我坚持使用非常基本的 Flutter 插件创建工具。另外，我不知道为什么我的包中需要所有肮脏而复杂的 example 子目录(所以作为一个并不重要的次要问题:我可以在这工作后将其删除吗？)

编辑:我做了另一个测试:使用 VSC 的“Flutter: New Project”命令创建了一个空应用程序(创建了“Flutter 101”增量计数器示例)。然后再次按照上述步骤创建插件包，并在新创建的项目中包含该包并在 iOS 模拟器中运行它时出现相同的错误。所以那里绝对没有我的代码，除了将新插件添加为示例应用程序的依赖项。

Answer 1

尝试用Xcode打开文件夹ios/Runner/Runner.xcworkspac中的IOS项目。然后在该目录的任何位置创建/添加一个新的 Swift 文件。然后 Xcode 将自动应用所需的更改以支持您的 Flutter 应用程序的 swift 部分。

另一件事可能是您的 PodFile 以某种方式被修改:尝试通过此链接将其与 Google 的主 PodFile 进行比较:PodFile Master File