android studio混淆批量打包编译出错问题，请大神来解答

各位大神，小弟刚刚接触android Studio，现在正在要开发做打包的工作，但是编译上却出了问题，希望大神帮忙解答，错误如下
FAILURE: Build failed with an exception.

• What went wrong:
  
  A problem occurred configuring root project 'android'.

  Could not resolve all dependencies for configuration ':classpath'.
  Could not find com.android.tools.build:gradle:2.2.1.
  Searched in the following locations:
  http://maven.oschina.net/content/groups/public/com/android/tools/build/gradle/2.2.1/gradle-2.2.1.pom
  http://maven.oschina.net/content/groups/public/com/android/tools/build/gradle/2.2.1/gradle-2.2.1.jar
  Required by:
  
  :android:unspecified

• Try:
  
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

希望大神能指出问题所在，谢谢了！