FLUTTER FIRST RUN：构建失败并出现异常

Question

我正在尝试通过 Genymotion 在 Flutter 上执行我的第一个 测试应用程序 run，但除了控制台中的这条消息外，我什么也没有收到：

Launching lib\main.dart on Motorola Moto X in debug mode...
Running Gradle task 'assembleDebug'...

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring root project 'android'.
> Could not resolve all artifacts for configuration ':classpath'.
   > Could not find com.android.tools.build:gradle:3.5.0.
     Searched in the following locations:
       - https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.5.0/gradle-3.5.0.pom
       - https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.5.0/gradle-3.5.0.jar
       - https://jcenter.bintray.com/com/android/tools/build/gradle/3.5.0/gradle-3.5.0.pom
       - https://jcenter.bintray.com/com/android/tools/build/gradle/3.5.0/gradle-3.5.0.jar
     Required by:
         project :

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 26s
Finished with error: Gradle task assembleDebug failed with exit code 1

另外（我认为这可能会有所帮助），在build menu 下，我没有找到一些实用的子菜单；例如build、clean 或...

可能是什么问题？

任何帮助都真的感激！

---

由于@TaufikNurRahmanda 需要 flutter doctor 和 flutter clean 命令的响应作为更多细节，我将它们添加为编辑；

扑医生：

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, v1.12.13+hotfix.7, on Microsoft Windows [Version 10.0.10586], locale en-US)

[!] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    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 3.4)
[√] IntelliJ IDEA Community Edition (version 2019.3)
[√] Connected device (1 available)

! Doctor found issues in 1 category.

干净利落：

Error: No pubspec.yaml file found.
This command should be run from the root of your Flutter project.
Do not run this command from the root of your git clone of Flutter.

---

flutter doctor --android-licenses 的回复也可能有用（虽然我安装了Android SDK Build-tools 29.0.3）：

A newer version of the Android SDK is required. To update, run: C:\Users\[user]\AppData\Local\Android\android-sdk\tools\bin\sdkmanager --update

当我运行上面建议的命令 (sdkmanager --update) 时，我得到了这个：

Error: Could not find or load main class '-Dcom.android.sdklib.toolsdir=C:\Users\[user]\AppData\Local\Android\android-sdk\tools\bin\\..-XX:+IgnoreUnrecognizedVMOptions 

Answer 1

您似乎不接受某些 android 许可证。运行：

flutter doctor --android-licenses

并接受y 的所有许可。