还尝试删除.gradle和gradle文件..
但这个问题仍然存在.

Error:Unable to find method
‘com.android.build.gradle.BaseExtension.getTestVariants()Lorg/gradle/api/internal/DefaultDomainObjectSet;’.
Possible causes for this unexpected error include:

• Gradle’s
  dependency cache may be corrupt (this sometimes occurs after a network
  connection timeout.) Re-download dependencies
  and sync project (requires network)
• The state of a Gradle
  build process (daemon) may be corrupt. Stopping all Gradle daemons may
  solve this problem. Stop Gradle build
  processes (requires restart)
• Your project may be using a
  third-party plugin which is not compatible with the other plugins in
  the project or the version of Gradle requested by the
  project.

In the case of corrupt Gradle processes,you can
also try closing the IDE and then killing all Java processes.

有什么想法吗？

感谢您的帮助！