title: FATAL Error in native method: Using JNIEnv in non-java thread
body: <p>I'm implementing some JNI callback (native -> java) functionality alongside another larger native framework and on one of the <em>framework's</em> callbacks I'm getting this error when trying to callback to <em>java</em>.</p>
  
  <pre><code>FATAL Error in native method: Using JNIEnv in non-java thread
  </code></pre>
  
  <p>What exactly does this mean? What is a java-thread and how do I go about using JNI in another native thread?</p>