title: How to use ProGuard in Library Module
body: <p>I want to enable ProGuard in library module but getting compilation error that package does not exists. Why package not exists after apply ProGuard in library module?</p>
  
  <p>library module build.gradle</p>
  
  <pre><code>buildTypes {
          release {
              minifyEnabled true
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  </code></pre>
  
  <p>Log Error</p>
  
  <pre><code> /home/hitesh/Documents/Android Studio Project/ALPR-Sample/app/src/main/java/com/alpr/sample/GalleryActivity.java
  Error:(15, 32) error: package com.alprlib.alpr.doc does not exist
  Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
  &gt; Compilation failed; see the compiler error output for details.
  </code></pre>
  
  <p>here doc class file exist in library module</p>
  
  <p>ProGuard file rules</p>
  
  <pre><code>-keep class com.alprlib.alpr.** { *; }
  -keepclassmembers class alprlib.alpr.** {*;}
  </code></pre>