title: cannot resolve symbol for v4 media and app classes
body: <p>I'm trying to <em>import</em> the following classes for my media player, but my app does not recognize them:</p>
  
  <pre><code>import android.support.v4.media.MediaMetadataCompat;
  import android.support.v4.media.session.MediaControllerCompat;
  import android.support.v4.media.session.MediaSessionCompat;
  import android.support.v7.app.NotificationCompat;
  </code></pre>
  
  <p>I've tried as others suggested <code>(File-&gt;Invalidate Caches/restart)</code>, but the error remains.</p>
  
  <p>gradle:</p>
  
  <pre><code>dependencies {
      implementation fileTree(dir: 'libs', include: ['*.jar'])
      implementation 'com.android.support:appcompat-v7:28.0.0-rc02'
      implementation 'com.android.support.constraint:constraint-layout:1.1.3'
      testImplementation 'junit:junit:4.12'
      androidTestImplementation 'com.android.support.test:runner:1.0.2'
      androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
  
      implementation 'com.android.support:recyclerview-v7:28.0.0-rc02'
      implementation 'com.android.support:cardview-v7:28.0.0-rc02'
      implementation 'com.android.support:design:28.0.0-rc02'
      implementation group: 'com.google.code.gson', name: 'gson', version: '2.7', changing: true
  }
  </code></pre>