title: Get javac to use androidx
body: <p>I am now coding Android apps without using Android Studio, and when I compile, I encountered the errors:</p>
  <blockquote>
  <p>./src/com/example/projectname/GamePanel.java:8: error: cannot find symbol
  import androidx.annotation.NonNull;</p>
  </blockquote>
  <p>where the &quot;^&quot; points at the period before &quot;NonNull&quot;, and</p>
  <blockquote>
  <p>error: package androidx.appcompat.app does not exist</p>
  </blockquote>
  <p>And my compile command is:</p>
  <p><code>javac -d obj -sourcepath src -classpath ../android/platforms/android-32/android.jar ./src/com/example/projectname/*.java</code></p>
  <p>The internet tells me that I should set android.useAndroidX to true, but I am not using Android Studio. Is there any way to let javac know that I am using AndroidX?</p>