Facebook authentication without login button

@erdomester, @sromku

Facebook launch new sdk version 4.x where Session is deprecated,

There new concept of login as from facebook

LoginManager and AccessToken - These new classes perform Facebook Login

So, Now you can access Facebook authentication without login button as

layout.xml

    <Button
            android:id="@+id/btn_fb_login"
            .../>

MainActivity.java

private CallbackManager mCallbackManager;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    FacebookSdk.sdkInitialize(this.getApplicationContext());

    mCallbackManager = CallbackManager.Factory.create();

    LoginManager.getInstance().registerCallback(mCallbackManager,
            new FacebookCallback<LoginResult>() {
                @Override
                public void onSuccess(LoginResult loginResult) {
                    Log.d("Success", "Login");

                }

                @Override
                public void onCancel() {
                    Toast.makeText(MainActivity.this, "Login Cancel", Toast.LENGTH_LONG).show();
                }

                @Override
                public void onError(FacebookException exception) {
                    Toast.makeText(MainActivity.this, exception.getMessage(), Toast.LENGTH_LONG).show();
                }
            });

    setContentView(R.layout.activity_main);

    Button btn_fb_login = (Button)findViewById(R.id.btn_fb_login);

    btn_fb_login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
              LoginManager.getInstance().logInWithReadPermissions(this, Arrays.asList("public_profile", "user_friends"));
        }
    });

}

Edit

If you don't add the following, it won't work (rightly pointed out by @Daniel Zolnai in comment below):

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if(mCallbackManager.onActivityResult(requestCode, resultCode, data)) {
        return;
    }
}

Something like this

private void performFacebookLogin()
{
    Log.d("FACEBOOK", "performFacebookLogin");
    final Session.NewPermissionsRequest newPermissionsRequest = new Session.NewPermissionsRequest(this, Arrays.asList("email"));
    Session openActiveSession = Session.openActiveSession(this, true, new Session.StatusCallback()
    {
        @Override
        public void call(Session session, SessionState state, Exception exception)
        {
            Log.d("FACEBOOK", "call");
            if (session.isOpened() && !isFetching)
            {
                Log.d("FACEBOOK", "if (session.isOpened() && !isFetching)");
                isFetching = true;
                session.requestNewReadPermissions(newPermissionsRequest);
                Request getMe = Request.newMeRequest(session, new GraphUserCallback()
                {
                    @Override
                    public void onCompleted(GraphUser user, Response response)
                    {
                        Log.d("FACEBOOK", "onCompleted");
                        if (user != null)
                        {
                            Log.d("FACEBOOK", "user != null");
                            org.json.JSONObject graphResponse = response.getGraphObject().getInnerJSONObject();
                            String email = graphResponse.optString("email");
                            String id = graphResponse.optString("id");
                            String facebookName = user.getUsername();
                            if (email == null || email.length() < 0)
                            {
                                Logic.showAlert(
                                        ActivityLogin.this,
                                        "Facebook Login",
                                        "An email address is required for your account, we could not find an email associated with this Facebook account. Please associate a email with this account or login the oldskool way.");
                                return;
                            }
                        }
                    }
                });
                getMe.executeAsync();
            }
            else
            {
                if (!session.isOpened())
                    Log.d("FACEBOOK", "!session.isOpened()");
                else
                    Log.d("FACEBOOK", "isFetching");

            }
        }
    });

Actually exactly like that. It works perfectly fine for me.

This worked for me

    import android.os.Bundle;
    import android.app.Activity;
    import android.content.Intent;
    import android.widget.TextView;
    import com.facebook.*;
    import com.facebook.model.*;

    public class MainActivity extends Activity {

      @Override
      public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // start Facebook Login
        Session.openActiveSession(this, true, new Session.StatusCallback() {

          // callback when session changes state
          @Override
          public void call(Session session, SessionState state, Exception exception) {
            if (session.isOpened()) {

              // make request to the /me API
              Request.newMeRequest(session, new Request.GraphUserCallback() {

                // callback after Graph API response with user object
                @Override
                public void onCompleted(GraphUser user, Response response) {
                  if (user != null) {
                    TextView welcome = (TextView) findViewById(R.id.welcome);
                    welcome.setText("Hello " + user.getName() + "!");
                  }
                }
              }).executeAsync();
            }
          }
        });
      }

      @Override
      public void onActivityResult(int requestCode, int resultCode, Intent data) {
          super.onActivityResult(requestCode, resultCode, data);
          Session.getActiveSession().onActivityResult(this, requestCode, resultCode, data);
      }

    }

if you need to get authorizations after verify that session is open ,add this way:

List<String> permissions = session.getPermissions();             
                 Session.NewPermissionsRequest newPermissionsRequest = new         Session.NewPermissionsRequest(getActivity(), Arrays.asList("read_mailbox"));
                 session.requestNewReadPermissions(newPermissionsRequest);