当我运行flutter doctor时，我注意到许可证状态未知。

[√] Flutter (Channel stable, v1.0.0, on Microsoft Windows [Version 10.0.17763.253], locale en-US)
[!] Android toolchain - develop for Android devices (Android SDK 28.0.3)
    X Android license status unknown.
[√] Android Studio (version 3.3)
[√] IntelliJ IDEA Ultimate Edition (version 2018.3)
[!] VS Code (version 1.30.2)
[!] Connected device
    ! No devices available

! Doctor found issues in 3 categories.

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我发现，为了解决许可证，我需要运行此命令flutter doctor --android-licenses.当我运行，我得到以下错误：

The system cannot find the path specified.
The system cannot find the path specified.
The system cannot find the path specified.
A newer version of the Android SDK is required. To update, run:
C:\Users\myusername\AppData\Local\Android\sdk\tools\bin\sdkmanager --update

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然后我试着运行C:\Users\myusername\AppData\Local\Android\sdk\tools\bin\sdkmanager --update，我收到了下面的错误：

'E\AppData\Local\Android\Sdk\tools\bin\' is not recognized as an internal or external command,
operable program or batch file.
Error: Could not find or load main class com.android.sdklib.tool.sdkmanager.SdkManagerCli

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我在网上到处找，找不到任何答案。我是新的Flutter，不知道如何解决这个问题。任何帮助将是伟大的感谢！