flutter doctor出現問題 [!] Android toolchain - develop for Android devices (Android SDK version 28.0.3)

首先，問題描述：

flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, v1.5.4-hotfix.2, on Microsoft Windows [Version 10.0.17134.765],
    locale zh-CN)
[!] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    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 3.2)
[√] VS Code (version 1.34.0)
[!] Connected device
    ! No devices available

! Doctor found issues in 2 categories.

解決辦法：

一、 Android SDK version 28

Android Studio -> SDK Manager -> SDK Platforms tab -> 選擇 Android 9.0 Pie 並安裝

二、Android BuildTools version 28.0.3

Android Studio -> SDK Manager -> SDK Tools tab -> 選擇右下角 Show Package Details -> 在 Android SDK Build-Tools 裏選擇 28.0.3 並下載

而後重啓Android studio，再在cmd裏輸入命令便可

參考連接：https://juejin.im/post/5d8c7be5f265da5b8305db5b