Google login works in emulator but not in phone
<p>I have a very serious problem with implementing Google sign in with Firebase.
I can log in with my emulator Android 7.0(SDK built for x86_64),
but if I upload my project to my phone (Android 6.0) I cannot log in with Google.
The only thing I see, is that the app closes. In rare situations, it will log in if I double-tap login button quickly, but won't get credentials for further use.
What might be the issue?</p>

<p><strong>The code in LoginActivity</strong></p>

<pre><code>@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if(requestCode == FirebaseConstants.LOG_IN_REQUEST){

        GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
        Intent i = new Intent(LoginActivity.this, MainActivity.class);
        startActivity(i);

    }
    if(requestCode == FirebaseConstants.LOG_OUT_REQUEST){
        TastyToast.makeText(this, "Logged out successfully", TastyToast.LENGTH_LONG, TastyToast.SUCCESS);
    }
}
</code></pre>

<p>Here is the code that is in the onCreate method (button click):</p>

<pre><code>    btnGoogleSignIn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(NetworkUtil.isNetworkAvailable(LoginActivity.this)){
                googleLogin.logIn(LoginActivity.this);
            }else{
                TastyToast.makeText(LoginActivity.this, "Network is unavailable", TastyToast.LENGTH_LONG, TastyToast.ERROR);
            }
        }
    });
</code></pre>

<p><strong>The google login instance</strong></p>

<pre><code>    public class GoogleLogin extends Observable implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener{

        private final GoogleApiClient googleApiClient;
        private final WeakReference&lt;Activity&gt; activityWeakReference;
        private static GoogleLogin googleLogin;

        public GoogleLogin(final Activity activity) {
            activityWeakReference = new WeakReference&lt;&gt;(activity);
            // Configure Google Sign In
            GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                    .requestIdToken(activity.getString(R.string.default_web_client_id))
                    .requestEmail()
                    .build();
            googleApiClient = new GoogleApiClient.Builder(activity)
                    .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                    .build();
        }

        @Override
        public void onConnected(@Nullable Bundle bundle) {
        }

        @Override
        public void onConnectionSuspended(int i) {

        }

        @Override
        public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
        }

        public static GoogleLogin getInstance(Activity activity) {
            if (null == googleLogin) {
                googleLogin = new GoogleLogin(activity);
            }

            return googleLogin;
        }


        public void logIn(Activity activity){
            Context c = activityWeakReference.get().getApplicationContext();
            googleApiClient.connect();
            if(googleApiClient.isConnected()){
                Intent i = new Intent(c, MainActivity.class);
                googleApiClient.connect();
                activity.startActivity(i); // this wont start an activity
            }else if(!googleApiClient.isConnected()){
                Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(googleApiClient);
                googleApiClient.connect();
// this wont start an activity either
                activity.startActivityForResult(signInIntent, FirebaseConstants.LOG_IN_REQUEST);



            }
        }

        public void signOut(final Activity activity){
            if(googleApiClient.isConnected()) {
                Auth.GoogleSignInApi.signOut(googleApiClient).setResultCallback(
                        new ResultCallback&lt;Status&gt;() {
                            @Override
                            public void onResult(Status status) {
                                Intent i = new Intent(activity, LoginActivity.class);
                                activity.startActivityForResult(i, FirebaseConstants.LOG_OUT_REQUEST);
                            }
                        });
            }
        }

        public void disconnect(Activity activity){
            activity.getApplicationContext();
            if(googleApiClient.isConnected()){
                googleApiClient.disconnect();
                Intent i = new Intent(activity, LoginActivity.class);
            }
        }


    }
</code></pre>

<p>I cannot fix this problem without your help guys. I really need to get it working!</p>

<p><strong>The dependencies in build.gradle</strong></p>

<pre><code>compile 'com.google.firebase:firebase-messaging:9.6.1'
compile 'com.google.firebase:firebase-database:9.6.1'
compile 'com.google.firebase:firebase-core:9.6.1'
compile 'com.google.firebase:firebase-auth:9.6.1'
compile 'com.google.android.gms:play-services-auth:9.6.1'
compile 'com.google.firebase:firebase-ads:9.6.1'
</code></pre>

<p><strong>At the bottom of build.gradle</strong></p>

<pre><code>apply plugin: 'com.google.gms.google-services'
</code></pre>