此解决方法实例化于中国大陆,需要将一些镜像更改为阿里云的镜像
maven { url 'https://maven.aliyun.com/repository/google' }
maven { url 'https://maven.aliyun.com/repository/jcenter' }
maven { url 'https://maven.aliyun.com/nexus/content/groups/public' }
Step1 打开 你的应用/android/gradle/build.gradle,按下图更改

Step2 打开 你的Flutter所在目录/flutter/packages/flutter_tools/gradle/flutter.gradle, 按下图更改

然后就行了
参考文献:
https://blog.csdn.net/jinglinggg/article/details/105383270
以上,曾实例化于Win10 21H2 + Flutter3.0.1 + VS Code