1.3.5　检查Flutter开发环境

在终端输入命令flutter doctor，输出如下信息：

 Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, v1.9.1+hotfix.6, on Mac OS X 10.14.6 18G1012,
    locale zh-Hans-CN)

[!] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    ! Some Android licenses not accepted.  To resolve this, run: flutter doctor
      --android-licenses
[√] Xcode - develop for iOS and macOS (Xcode 11.2.1)
[√] Android Studio (version 3.5)
[√] Connected device (1 available)

! Doctor found issues in 1 category.

运行结果表明没有缺失的环境，如果出现红色叉，则需要我们解决问题。