title: java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.google.android.gms.ads.identifier.d.a' on a null object reference:
body: <blockquote>
    <p>Unable to get advertising id: java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.google.android.gms.ads.identifier.d.a' on a null object reference: ufv.a(:com.google.android.gms:3134)</p>
  </blockquote>
  
  <p>I have searched Stack Overflow and Google for a solution but no luck; as well as the error above I was also getting the same error as
  <a href="https://stackoverflow.com/questions/37604283/android-studio-attempt-to-setonclicklistener-on-a-null-object-reference">Android Studio: Attempt to setOnClickListener on a null object reference</a>, but the solution did not help and that error seems to come and go.</p>
  
  <p>I am trying to implement sign in with Google following a tutorial on YouTube, I have done everything the same however my app closes on launch.</p>
  
  <p>I think the error is related to this line of the code, but I am not sure.</p>
  
  <pre><code>    findViewById(R.id.sign_in_button).setOnClickListener(this);
  </code></pre>
  
  <p>Below is the rest of the code.</p>
  
  <pre><code>protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_instructors);
          mAuth = FirebaseAuth.getInstance();
  
          mAuthListener = new FirebaseAuth.AuthStateListener() {
              @Override
              public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                  FirebaseUser user = firebaseAuth.getCurrentUser();
                  if(user != null)
                      Log.d ("AUTH", "user Logged in: " + user.getEmail());
                  else
                      Log.d("AUTH", "user logged out.");
              }};
  
          GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                  .requestIdToken(getString(R.string.default_web_client_id))
                  .requestEmail()
                  .build();
          mGoogleApiClient = new GoogleApiClient.Builder(this)
                  .enableAutoManage(this, this)
                  .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                  .build();
  
          findViewById(R.id.sign_in_button).setOnClickListener(this);
  </code></pre>
  
  <p>and the xml for the sign_in_button is:</p>
  
  <pre><code>&lt;com.google.android.gms.common.SignInButton
              android:id="@+id/sign_in_button"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"/&gt;
  </code></pre>
  
  <p>This is the logcat:</p>
  
  <pre><code>01-16 23:02:49.226 1757-24616/com.actionlauncher.playstore V/FA: Activity paused, time: 35229566
  01-16 23:02:50.236 1757-24616/com.actionlauncher.playstore D/FA: Application backgrounded. Logging engagement
  01-16 23:02:50.238 1757-24616/com.actionlauncher.playstore D/FA: Logging event (FE): _e, Bundle[{_o=auto, _et=293642}]
  01-16 23:02:50.239 1757-24616/com.actionlauncher.playstore V/FA: Using measurement service
  01-16 23:02:50.239 1757-24616/com.actionlauncher.playstore V/FA: Connecting to remote service
  01-16 23:02:50.254 1757-24616/com.actionlauncher.playstore D/FA: Connected to remote service
  01-16 23:02:50.254 1757-24616/com.actionlauncher.playstore V/FA: Processing queued up service tasks: 1
  01-16 23:02:50.261 1811-24637/com.google.android.gms V/FA-SVC: Logging event: origin=auto,name=_e,params=Bundle[mParcelledData.dataSize=60]
  01-16 23:02:50.271 1811-24637/com.google.android.gms D/FA-SVC: Unable to get advertising id: java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.google.android.gms.ads.identifier.d.a' on a null object reference: ufv.a(:com.google.android.gms:3134)
  01-16 23:02:50.289 1811-24637/com.google.android.gms V/FA-SVC: Saving event, name, data size: _e, 30
  01-16 23:02:50.290 1811-24637/com.google.android.gms V/FA-SVC: Event recorded: Event{appId='com.actionlauncher.playstore', name='_e', params=Bundle[{_o=auto, _et=293642}]}
  01-16 23:02:50.310 1811-24637/com.google.android.gms V/FA-SVC: Upload scheduled in approximately ms: 1956907
  01-16 23:02:50.317 1811-24637/com.google.android.gms V/FA-SVC: Background event processing time, ms: 56
  01-16 23:02:55.263 1757-24616/com.actionlauncher.playstore V/FA: Inactivity, disconnecting from AppMeasurementService
  01-16 23:03:59.719 1757-25003/com.actionlauncher.playstore V/FA: Activity resumed, time: 35300060
  01-16 23:04:05.460 1757-25003/com.actionlauncher.playstore V/FA: Activity paused, time: 35305801
  01-16 23:04:06.462 1757-25003/com.actionlauncher.playstore D/FA: Application backgrounded. Logging engagement
  01-16 23:04:06.466 1757-25003/com.actionlauncher.playstore D/FA: Logging event (FE): _e, Bundle[{_o=auto, _et=5741}]
  01-16 23:04:06.466 1757-25003/com.actionlauncher.playstore V/FA: Using measurement service
  01-16 23:04:06.466 1757-25003/com.actionlauncher.playstore V/FA: Connecting to remote service
  01-16 23:04:06.474 1757-25003/com.actionlauncher.playstore D/FA: Connected to remote service
  01-16 23:04:06.474 1757-25003/com.actionlauncher.playstore V/FA: Processing queued up service tasks: 1
  01-16 23:04:06.478 1811-25093/com.google.android.gms V/FA-SVC: Logging event: origin=auto,name=_e,params=Bundle[mParcelledData.dataSize=60]
  01-16 23:04:06.483 1811-25093/com.google.android.gms D/FA-SVC: Unable to get advertising id: java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.google.android.gms.ads.identifier.d.a' on a null object reference: ufv.a(:com.google.android.gms:3134)
  01-16 23:04:06.490 1811-25093/com.google.android.gms V/FA-SVC: Saving event, name, data size: _e, 29
  01-16 23:04:06.490 1811-25093/com.google.android.gms V/FA-SVC: Event recorded: Event{appId='com.actionlauncher.playstore', name='_e', params=Bundle[{_o=auto, _et=5741}]}
  01-16 23:04:06.529 1811-25093/com.google.android.gms V/FA-SVC: Upload scheduled in approximately ms: 1880688
  01-16 23:04:06.532 1811-25093/com.google.android.gms V/FA-SVC: Background event processing time, ms: 54
  </code></pre>