title: Gradle error for java library module in Android Studio
body: <p>In my Android Studio project, there are 2 modules: an android app module and a java library module, they all worked. But after I upgraded the Android Studio and Gradle, the java library module doesn't work.</p>
  
  <pre><code>Error:Gradle: A problem occurred configuring root project 'demo'.
   &gt; Could not resolve all dependencies for configuration ':classpath'.
   &gt; Could not resolve com.android.tools.build:gradle:2.0.0.
   Required by:
       :demo:unspecified
    &gt; No cached version of com.android.tools.build:gradle:2.0.0 available for  offline mode.
  </code></pre>
  
  <p>If there is no com.android.tools.build:gradle:2.0.0 in my Android Studio, why the android app module works normally?</p>