按照flutter安装步骤一步步执行
执行flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.12.13+hotfix.8, on Mac OS X 10.15.3 19D76, locale zh-Hans-CN)
[!] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
✗ 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.
[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
[✓] Android Studio (version 3.6)
[✓] VS Code (version 1.42.1)
[✓] Connected device (3 available)
! Doctor found issues in 1 category.
一直报错 Android license status unknown。
网上有很多执行flutter doctor --android-licenses命令，然后一路y就能解决问题的，对我没用。
我执行以后显示的是：
flutter doctor --android-licenses
Android sdkmanager tool not found (/Users/suying/Library/Android/sdk/tools/bin/sdkmanager).
Try re-installing or updating your Android SDK,
visit https://flutter.dev/setup/#android-setup for detailed instructions.
还有说在将 android-sdk/emulator/bin 目录拷贝至 android-sdk/tools/，我发现android/sdk/路径下压根没有tools文件夹。我想可能是我android环境变量配置有问题，后来在.bash_profile配置ANDROID_HOME和PATH等变量，问题还是没有解决。
又尝试在Android Studio中SDK Platform和SDK Tools 下载各种SDK，依然没有起作用。
后来在stackoverflow发现一个回答：
I had this issue when I installed on KUbuntu. You need to open AndioStudio In SDK Manager -> SDK Tools uncheck 'Hide Obsolete packages.. download and install Android SDK Tools(Obsolete).
Android Studio SDK Manager
默认Hide Obsolete是选中的，将其选中给取消，然后下载Android SDK Tools(Obsolete)，下载完以后/Users/suying/Library/Android/sdk这个路径下出现了tools文件夹，再执行flutter doctor，就完全没有问题了。
