title: Dex: Error converting bytecode to dex: Cause: Dex cannot parse version 52 byte code in unity andorid build
body: <p>I have implement Tensorflow Android as a unity plugin. After building aar and integrate to Unity project, i get error:</p>
  
  <pre><code>CommandInvokationFailure: Gradle build failed. 
  /Library/Java/JavaVirtualMachines/jdk1.8.0_162.jdk/Contents/Home/bin/java -classpath "/Applications/Unity/PlaybackEngines/AndroidPlayer/Tools/gradle/lib/gradle-launcher-4.0.1.jar" org.gradle.launcher.GradleMain "-Dorg.gradle.jvmargs=-Xmx2048m" "assembleRelease"
  
  stderr[
  Dex: Error converting bytecode to dex:
  Cause: Dex cannot parse version 52 byte code.
  This is caused by library dependencies that have been compiled using Java 8 or above.
  If you are using the 'java' gradle plugin in a library submodule add 
  targetCompatibility = '1.7'
  sourceCompatibility = '1.7'
  to that submodule's build.gradle
  </code></pre>
  
  <p>I have got aar tensorflow file in: <a href="https://jcenter.bintray.com/org/tensorflow/tensorflow-android/1.8.0/" rel="nofollow noreferrer">https://jcenter.bintray.com/org/tensorflow/tensorflow-android/1.8.0/</a>
  and copy to Assets/Plugin but it still get this error.
  I am stuck in a day and can not come out problem.</p>