title: Pro-guard Obfuscation not working in android studio
body: <p>Using Latest Android Studio and having updated all platform ( OsX) :</p>
  
  <p>Build.gradle :</p>
  
  <pre><code>android {
  compileSdkVersion 26
  defaultConfig {
      applicationId "com.xxxxxxlxxxxxx.apps.firebase"
      minSdkVersion 16
      targetSdkVersion 26
      versionCode 1
      versionName "1.0"
      testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  }
  buildTypes {
      release {
          minifyEnabled true
          proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
      }
  }
  }
  
  dependencies {
  implementation fileTree(dir: 'libs', include: ['*.jar'])
  implementation 'com.android.support:appcompat-v7:26.1.0'
  implementation 'com.android.support:design:26.1.0'
  implementation 'com.android.support.constraint:constraint-layout:1.1.2'
  implementation 'com.firebase:firebase-jobdispatcher:0.8.5'
  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'
  }
  </code></pre>
  
  <hr>
  
  <p>Proguard-rules.pro :</p>
  
  <pre><code>-keep public class OpenSource
  </code></pre>
  
  <hr>
  
  <p>As you can see proguard is enabled and rules also given for just keeping <code>OpenSource</code> class. Still when i build its apk / signed apk. And uses following commands on apk file :</p>
  
  <ol>
  <li>Unzip apk</li>
  <li>sh Dex2jar.sh classes.dex</li>
  <li>And by opening output jar file with Jd-GUI </li>
  <li>I get all all my classes right from MainActivity and rest all, as it is. There is no Obfuscation seen working</li>
  </ol>
  
  <p>It would be very nice to have your suggestions on it. Thanks.</p>