今天执行 flutter doctor -v 的时候发现一个问题，提示信息是
[!] Android toolchain – develop for Android devices (Android SDK version 30.0.2)
• Android SDK at /Users/zhaopingfu/Library/Android/sdk
• Platform android-S, build-tools 30.0.2
• 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.
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然后根据提示信息执行 flutter doctor –android-licenses，发现报错了，错误信息是
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:522)
… 5 more
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通过 java -version 查看了 java 版本是 1.8
java version “1.8.0_281”
Java(TM) SE Runtime Environment (build 1.8.0_281-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.281-b09, mixed mode)
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网上好多说是 jdk 版本的问题，但是我的 jdk 就是 1.8，尝试了 jdk 升级到 11 再回退到 1.8 还是不行，所以排除这种情况
最后通过查找各种资料找到了解决办法
打开 AndroidStudio 中的 SdkManager
下载最新版本的 Android SDK Command-lines Tools，如下图所示
重新运行 flutter doctor –android-licenses，提示信息为
[========= ] 25% Fetch remote repository…
7 of 9 SDK package licenses not accepted. 100% Computing updates…
Review licenses that have not been accepted (y/N)?
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运行 flutter doctor -v，提示信息为
• No issues found!
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参考资料: https://www.dev2qa.com/how-to-fix-java-lang-noclassdeffounderror-javax-xml-bind-annotation-xmlschema-when-install-android-sdk/