title: Firebase error: cannot acces zzans
body: <p>I develop an android app with use of Firebase. And when I want to build my project I get error in the <code>OnCreateView()</code> method on initializing, I get the error:</p>
  
  <blockquote>
    <p>Error:(69, 36) error: cannot access zzans
    class file for com.google.android.gms.internal.zzans not found</p>
  </blockquote>
  
  <pre><code>firebaseAuth = FirebaseAuth.getInstance();
  firebaseAuthListener = new FirebaseAuth.AuthStateListener()
  </code></pre>
  
  <p>LoginActivity</p>
  
  <pre><code>import android.content.Intent;
  import android.os.Bundle;
  import android.support.annotation.NonNull;
  import android.support.v7.app.AppCompatActivity;
  import android.view.View;
  import android.widget.ProgressBar;
  import android.widget.Toast;
  
  import com.google.android.gms.auth.api.Auth;
  import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
  import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
  import com.google.android.gms.auth.api.signin.GoogleSignInResult;
  import com.google.android.gms.common.ConnectionResult;
  import com.google.android.gms.common.SignInButton;
  import com.google.android.gms.common.api.GoogleApiClient;
  import com.google.android.gms.tasks.OnCompleteListener;
  import com.google.android.gms.tasks.Task;
  import com.google.firebase.auth.AuthCredential;
  import com.google.firebase.auth.AuthResult;
  import com.google.firebase.auth.FirebaseAuth;
  import com.google.firebase.auth.FirebaseUser;
  import com.google.firebase.auth.GoogleAuthProvider;
  
  public class LogInActivity extends AppCompatActivity implements GoogleApiClient.OnConnectionFailedListener {
  
      private GoogleApiClient googleApiClient;
  
      private SignInButton signInButton;
  
      public static final int SIGN_IN_CODE = 777;
  
      private FirebaseAuth firebaseAuth;
      private FirebaseAuth.AuthStateListener firebaseAuthListener;
  
      private ProgressBar progressBar;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_login);
  
          GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                  .requestIdToken(getString(R.string.default_web_client_id))
                  .requestEmail()
                  .build();
  
          googleApiClient = new GoogleApiClient.Builder(this)
                  .enableAutoManage(this, this)
                  .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                  .build();
  
          signInButton = (SignInButton) findViewById(R.id.signInButton);
  
          signInButton.setSize(SignInButton.SIZE_WIDE);
  
          signInButton.setColorScheme(SignInButton.COLOR_DARK);
  
          signInButton.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View v) {
                  Intent intent = Auth.GoogleSignInApi.getSignInIntent(googleApiClient);
                  startActivityForResult(intent, SIGN_IN_CODE);
              }
          });
  
  
          firebaseAuth = FirebaseAuth.getInstance();
          firebaseAuthListener = new FirebaseAuth.AuthStateListener() {
              @Override
              public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                  FirebaseUser user = firebaseAuth.getCurrentUser();
                  if (user != null) {
                      goMainScreen();
                  }
              }
          };
  
          progressBar = (ProgressBar) findViewById(R.id.progressBar);
      }
  
      @Override
      protected void onStart() {
          super.onStart();
  
          firebaseAuth.addAuthStateListener(firebaseAuthListener);
      }
  
      @Override
      public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
  
      }
  
      @Override
      protected void onActivityResult(int requestCode, int resultCode, Intent data) {
          super.onActivityResult(requestCode, resultCode, data);
  
          if (requestCode == SIGN_IN_CODE) {
              GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
              handleSignInResult(result);
          }
      }
  
      private void handleSignInResult(GoogleSignInResult result) {
          if (result.isSuccess()) {
              firebaseAuthWithGoogle(result.getSignInAccount());
          } else {
              Toast.makeText(this, R.string.not_log_in, Toast.LENGTH_SHORT).show();
          }
      }
  
      private void firebaseAuthWithGoogle(GoogleSignInAccount signInAccount) {
  
          progressBar.setVisibility(View.VISIBLE);
          signInButton.setVisibility(View.GONE);
  
          AuthCredential credential = GoogleAuthProvider.getCredential(signInAccount.getIdToken(), null);
          firebaseAuth.signInWithCredential(credential).addOnCompleteListener(this, new OnCompleteListener&lt;AuthResult&gt;() {
              @Override
              public void onComplete(@NonNull Task&lt;AuthResult&gt; task) {
  
                  progressBar.setVisibility(View.GONE);
                  signInButton.setVisibility(View.VISIBLE);
  
                  if (!task.isSuccessful()) {
                      Toast.makeText(getApplicationContext(), R.string.not_firebase_auth, Toast.LENGTH_SHORT).show();
                  }
              }
          });
      }
  
      private void goMainScreen() {
          Intent intent = new Intent(this, MainActivity.class);
          intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
          startActivity(intent);
      }
  
      @Override
      protected void onStop() {
          super.onStop();
  
          if (firebaseAuthListener != null) {
              firebaseAuth.removeAuthStateListener(firebaseAuthListener);
          }
      }
  }
  </code></pre>
  
  <p>Gradle</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 25
      buildToolsVersion "25.0.2"
      defaultConfig {
          applicationId "kz.brainpull.googleauth"
          minSdkVersion 19
          targetSdkVersion 25
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
          exclude group: 'com.android.support', module: 'support-annotations'
      })
      compile 'com.android.support:appcompat-v7:25.3.1'
      testCompile 'junit:junit:4.12'
  
      compile 'com.google.android.gms:play-services-auth:10.2.1'
      compile 'com.google.firebase:firebase-auth:9.8.0'
      compile 'com.github.bumptech.glide:glide:3.7.0'
      compile 'com.google.firebase:firebase-core:9.2.0'
      compile 'com.google.firebase:firebase-messaging:9.2.0'
  }
  apply plugin: 'com.google.gms.google-services'
  </code></pre>
  
  <p>Help me to solve that error, please)</p>