public class LoginActivity extends AppCompatActivity {

    private static final int RC_SIGN_IN = 343;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        
        //I rather using a list, this way handling providers is separeted from the login methods
        List<AuthUI.IdpConfig> providers = Arrays.asList(
                new AuthUI.IdpConfig.EmailBuilder().build(),
                new AuthUI.IdpConfig.GoogleBuilder().build(),
                new AuthUI.IdpConfig.FacebookBuilder().build()
        );
        startActivityForResult(
                AuthUI.getInstance()
                        .createSignInIntentBuilder()
                        .setAvailableProviders(providers)                        
                        .setTheme(R.style.LoginTheme)
                        .setLogo(R.mipmap.logo)
                        .build(),
                RC_SIGN_IN);
    }
}