title: Failed to resolve Gradle Android Studio
body: <p>I want to add some third-party libraries, but I always got the "Failed to resolve" error.
  I tried some suggestions I found here, like:
  <a href="https://stackoverflow.com/questions/32519219/error23-17-failed-to-resolve-junitjunit4-12">Error:(23, 17) Failed to resolve: junit:junit:4.12</a> , 
  <a href="https://stackoverflow.com/questions/28493470/gradle-failed-to-resolve-library-in-android-studio">Gradle failed to resolve library in Android Studio</a>
  and <a href="https://stackoverflow.com/questions/29118606/gradle-in-android-studio-failed-to-resolve-third-party-libraries">Gradle in Android Studio: Failed to resolve third-party libraries</a>
  but it didn't work! how can I solve the problem? thanks in advance
  <a href="https://i.stack.imgur.com/DuN40.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DuN40.png" alt="enter image description here"></a></p>