在配置Flutter开发环境时，执行以下命令：
flutter doctor
然后报了下面这个错误
Android toolchain - develop for Android devices (Android SDK version 30.0.2) ✗ Android license status unknown. Try re-installing or updating your Android SDK Manager. See https://developer.android.com/studio/#downloads or visit visit https://flutter.dev/docs/get-started/install/macos#android-setup for detailed instructions.
按正常流程执行
flutter doctor --android-licensesr
然后又发现出现了这个问题
Exception in thread "main" java.lang.NoClassDefFoundError: javax/xml/bind/annotation/XmlSchema
at com.android.repository.api.SchemaModule$SchemaModuleVersion.<init>(SchemaModule.java:156)
at com.android.repository.api.SchemaModule.<init>(SchemaModule.java:75)
at com.android.sdklib.repository.AndroidSdkHandler.<clinit>(AndroidSdkHandler.java:81)
at com.android.sdklib.tool.sdkmanager.SdkManagerCli.main(SdkManagerCli.java:73)
at com.android.sdklib.tool.sdkmanager.SdkManagerCli.main(SdkManagerCli.java:48)
Caused by: java.lang.ClassNotFoundException: javax.xml.bind.annotation.XmlSchema
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
... 5 more
google一通，最后找到解决方案
打开android studio ，preferences -- android sdk -- sdk tools ，安装 android sdk command-line tools，点击apply。
重新执行
flutter doctor
搞定。
最后说下我的开发环境
jdk 11.0.2
android studio 4.2.1
flutter 2.2.1
macos 11.2.3
感谢stackoverflow原博主
