flutter doctor X Android license status unknown.

问题：当在window上搭建flutter开发环境，最后运行flutter doctor -v时，出现提示：

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, v1.9.1+hotfix.5, on Microsoft Windows [Version 10.0.17763.316], locale zh-CN)
[!] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    X Android license status unknown.
      Try re-installing or updating your Android SDK Manager.
      See https://developer.android.com/studio/#downloads or visit https://flutter.dev/setup/#android-setup for detailed instructions.
[√] Android Studio (version 3.5)
[√] VS Code (version 1.39.2)
[!] Connected device
    ! No devices available

解决方法：

按照提示升级sdk manager

打开命令行窗口，讲目录切换到Android sdk 目录下：AndroidSdk\tools\bin
运行一下命令

sdkmanager --update

D:\tools\Android\AndroidSdk\tools\bin>sdkmanager --update