title: How to stop firebase error in flutter app
body: <p>my app isn't building again, don't know what I did wrong. The error message  is listed below</p>
  <pre><code>C:\flutter\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_auth-0.8.0+1\android\src\main\java\io\flutter\plugins\firebaseauth\FirebaseAuthPlugin.java:9: error: package androidx.annotation does not exist
  import androidx.annotation.NonNull;
                            ^
  C:\flutter\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_auth-0.8.0+1\android\src\main\java\io\flutter\plugins\firebaseauth\FirebaseAuthPlugin.java:10: error: package androidx.annotation does not exist
  import androidx.annotation.Nullable;
                            ^
  C:\flutter\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_auth-0.8.0+1\android\src\main\java\io\flutter\plugins\firebaseauth\FirebaseAuthPlugin.java:638: error: cannot find symbol
  </code></pre>