Could not resolve io.flutter

打包Android APK是发生这类错误，主要是io.flutter库没有下载下来，重新配置一下国内的资源

buildscript { ext.kotlin_version = '1.3.50'

 repositories {

 // google()

 // jcenter()

 maven { url 'http://maven.aliyun.com/nexus/content/repositories/google' }

 maven { url 'http://maven.aliyun.com/nexus/content/repositories/jcenter' } 

 maven { url 'https://jitpack.io' }

 }

}

allprojects { 

 repositories { 

 // google() 

 // jcenter()

 maven { url 'http://maven.aliyun.com/nexus/content/repositories/google' }

 maven { url 'http://maven.aliyun.com/nexus/content/repositories/jcenter' }

 maven { url 'https://jitpack.io' } 

 maven { url "https://storage.googleapis.com/download.flutter.io" }

 }//这句是为了解决io.flutter异常问题}

这样可以提高运行编译速度，也解决了io.flutter异常问题