我通过在xxx.podspec中添加以下代码行来使我的代码工作：

s.preserve_paths = 'xxxxxx.xcframework/**/*'
s.xcconfig = { 'OTHER_LDFLAGS' => '-framework xxxxxx' }
s.vendored_frameworks = 'xxxxxx.xcframework'

请注意s.preserve_paths末尾的/**/*
下面是完整的xxx.podspec文件：

#
# To learn more about a Podspec see http://guides.cocoapods.org/syntax/podspec.html.
# Run `pod lib lint xxx.podspec` to validate before publishing.
#
Pod::Spec.new do |s|
  s.name             = 'xxx'
  s.version          = '1.0.0'
  s.summary          = 'xxx'
  s.description      = <<-DESC
xxx is a flutter plugin
                       DESC
  s.homepage         = 'https://example.com'
  s.license          = { :file => '../LICENSE', :type => 'BSD' }
  s.author           = { 'xxx' => 'email@example.com' }
  s.source           = { :path => '.' }
  s.source_files = 'Classes/**/*'
  s.dependency 'Flutter'
  s.platform = :ios, '10.0'

  # Flutter.framework does not contain a i386 slice.
  s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES', 'EXCLUDED_ARCHS[sdk=iphonesimulator*]' => 'i386' }
  s.swift_version = '5.0'

  s.preserve_paths = 'xxxxxx.xcframework/**/*'
  s.xcconfig = { 'OTHER_LDFLAGS' => '-framework xxxxxx' }
  s.vendored_frameworks = 'xxxxxx.xcframework'
end

确保将xxxxxx.xcframework目录复制到.../xxx/ios/xxxxxx.xcframework（您的xxx.podspec插件所在的位置）

将xxxxxx.xcframework添加到Pods方案以便能够导入它

运行flutter命令创建插件ie时，Frameworks目录应该在Pods方案下。
flutter create --org com.xxx --template=plugin --platforms=android,ios -a java -i swift xxx个
来源：开发软件包和插件

• （如果没有，请添加）*

1.导航到Pods方案，然后右键单击Frameworks
1.单击Add Files to "Pods"...

1.导航到xxxxxx.xcframework所在的ios目录的根目录
1.取消选中Copy items if needed
1.选择Create folder references
1.检查Pods-Runner
1.检查您的插件ie. xxx
1.单击Add

将xxxxxx.xcframework嵌入到项目中

• （这应该允许您运行/发布到实际设备）*

1.点击Pods方案
1.在TARGETS中选择Pods-Runner
1.单击General选项卡
1.确保xxxxx.xcframework位于Frameworks and Libraries下方（如果没有，请单击+添加）
1.将Embed更改为Embed & Sign

1.点击你的插件，即xxx
1.确保Frameworks and Libraries下面有xxxxx.xcframework
1.将Embed更改为Embed & Sign
x1c4d 1x指令集
1.同样，对于Pods scheme下面的两个目标，接下来的步骤应该已经很好了，但只需检查一下
1.单击Build Phases
1.单击Link Binary With Libraries
1.确保xxxxx.xcframework存在，如果不存在，请单击+添加xxxxx.xcframework，并将Status设置为Required
现在，您应该能够导入框架并在代码中引用它，并且还应该可以完美地发布。
希望这能有所帮助，祝你好运。我希望这不会很快再次改变

• 祈祷吧 *

在做了一些研究之后，我发现some links给了我一个关于真正问题的想法...
为了解决这个问题，我在主项目的构建过程中添加了一个简单的脚本。
此脚本将代码签名添加到内部.framework文件。

cd "${CODESIGNING_FOLDER_PATH}/Frameworks/"

# flatten nested frameworks by copying to APP.app/Frameworks
for framework in *; do
    if [ -d "$framework" ]; then
        if [ -d "${framework}/Frameworks" ]; then
            echo "Moving embedded frameworks from ${framework} to ${PRODUCT_NAME}.app/Frameworks"
            cp -R "${framework}/Frameworks/" .
            rm -rf "${framework}/Frameworks"
        fi
    fi
done

# remove any leftover nested frameworks (i.e. 'PackageName_359AFEED79E48935_PackageProduct.framework')
for framework in *; do
    if [ -d "$framework" ]; then
        if [ -d "${framework}/Frameworks" ]; then
            echo "Removing embedded frameworks from ${framework} to ${PRODUCT_NAME}.app/Frameworks"
            rm -rf "${framework}/Frameworks"
        fi
    fi
done

# codesign for Debugging on device
if [ "${CONFIGURATION}" == "Debug" ] & [ "${SDKROOT}" != *Simulator* ] ; then

    echo "Code signing frameworks..."
    find "${CODESIGNING_FOLDER_PATH}/Frameworks" -maxdepth 1 -name '*.framework' -print0 | while read -d $'\0' framework
    do
        # only sign frameworks without a signature
        if ! codesign -v "${framework}"; then
            codesign --force --sign "${EXPANDED_CODE_SIGN_IDENTITY}" --preserve-metadata=identifier,entitlements --timestamp=none "${framework}"
            echo "Added missing signature to '${framework}'"
        fi
    done
fi

如果以上修复都不起作用，但仍然出现类似“framework xxx not found”的错误，请验证xxx.xcframework和xxx.framework文件夹是否同名。
我花了几天时间未能将.xcframework添加到Flutter插件中，结果发现命名不匹配。