Flutter踩坑之 Could not find io.flutter.....

用AS打开Flutter项目Android模块，然后build，结果报错如下：

Could not resolve all files for configuration ':app:debugCompileClasspath'.
> Could not resolve io.flutter:flutter_embedding_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
  Required by:
      project :app
   > Could not resolve io.flutter:flutter_embedding_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/flutter_embedding_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/flutter_embedding_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:flutter_embedding_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/flutter_embedding_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/flutter_embedding_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:flutter_embedding_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/flutter_embedding_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/flutter_embedding_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
> Could not resolve io.flutter:arm64_v8a_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
  Required by:
      project :app
   > Could not resolve io.flutter:arm64_v8a_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/arm64_v8a_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/arm64_v8a_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:arm64_v8a_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/arm64_v8a_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/arm64_v8a_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:arm64_v8a_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/arm64_v8a_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/arm64_v8a_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
> Could not resolve io.flutter:x86_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
  Required by:
      project :app
   > Could not resolve io.flutter:x86_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/x86_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/x86_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:x86_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/x86_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/x86_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:x86_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/x86_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/x86_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
> Could not resolve io.flutter:x86_64_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
  Required by:
      project :app
   > Could not resolve io.flutter:x86_64_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/x86_64_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/x86_64_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:x86_64_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/x86_64_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/x86_64_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.
   > Could not resolve io.flutter:x86_64_debug:1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.
      > Could not parse POM http://download.flutter.io/io/flutter/x86_64_debug/1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94/x86_64_debug-1.0.0-e7f9ef6aa0b9040102d1b3c9a6ae934df746ef94.pom
         > Already seen doctype.

解决办法：

Android项目的build.gradle 

allprojects {
    repositories {
        ......
       //添加这一行
        maven { url "https://storage.googleapis.com/download.flutter.io" }
    }
}

重新build,完成

参考地址：https://github.com/flutter/flutter/issues/39729