環境

Xcode 12.5
Android Studio 4.2.1

エラーが起きた背景

FlutterをVSCodeで使用するため、flutter doctor -v コマンドを入れた時下記ような事が出てきた。

$ flutter doctor -v 
[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at /Users/Username/Library/Android/sdk
    • Platform android-30, build-tools 30.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6916264)
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/macos#android-setup for more details.

エラー内容

$ flutter doctor --android-licenses
Exception in thread "main" java.lang.NoClassDefFoundError: javax/xml/bind/annotation/XmlSchema
    at com.android.repository.api.SchemaModule$SchemaModuleVersion.<init>(SchemaModule.java:156)
    at com.android.repository.api.SchemaModule.<init>(SchemaModule.java:75)
    at com.android.sdklib.repository.AndroidSdkHandler.<clinit>(AndroidSdkHandler.java:81)
    at com.android.sdklib.tool.sdkmanager.SdkManagerCli.main(SdkManagerCli.java:73)
    at com.android.sdklib.tool.sdkmanager.SdkManagerCli.main(SdkManagerCli.java:48)
Caused by: java.lang.ClassNotFoundException: javax.xml.bind.annotation.XmlSchema
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    ... 5 more

##解決方法

Android Studioを開く
Tools -> SDK Managerをクッリク
Appearance & Behavior > System Settings > Android SDK
SDK ToolsからAndroid SDK Command-line tools (latest)をチェックしてインストールする

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at /Users/Username/Library/Android/sdk
    • Platform android-30, build-tools 30.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6916264)
    • All Android licenses accepted.

###参考
https://stackoverflow.com/questions/61993738/flutter-doctor-android-licenses-gives-a-java-error