Facebook login in SDK v 4.0

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <com.facebook.login.widget.LoginButton
        android:id="@+id/login_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="30dp"
        android:layout_marginBottom="30dp" />

</RelativeLayout>

mainactivity.java

//Necessary imports
...

//Facebook imports
import com.facebook.AccessToken;
import com.facebook.AccessTokenTracker;
import com.facebook.CallbackManager;
import com.facebook.FacebookSdk;
import com.facebook.Profile;
import com.facebook.login.widget.LoginButton;


public class MainActivity extends ActionBarActivity {

    CallbackManager callbackManager;
    LoginButton loginButton;
    AccessTokenTracker accessTokenTracker;

    //Constants
    public static int SPLASH_TIME_OUT = 2000;
    String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FacebookSdk.sdkInitialize(getApplicationContext());
        callbackManager = CallbackManager.Factory.create();

        setContentView(R.layout.activity_main);
        
        loginButton = (LoginButton) findViewById(R.id.login_button);

        //Init Access token Tracker
        //This method tracks the tokens and updates login/logout status
        updateWithToken(AccessToken.getCurrentAccessToken());

        //Token Tracker
        accessTokenTracker = new AccessTokenTracker() {
            @Override
            protected void onCurrentAccessTokenChanged(AccessToken oldAccessToken, AccessToken newAccessToken) {
                updateWithToken(newAccessToken); 
            }
        };
    }

    private void updateWithToken(AccessToken currentAccessToken) {

        if (currentAccessToken != null) {
            new Handler().postDelayed(new Runnable() {

                @Override
                public void run() {
                    //Use Intent to forward to screen where user should be, once logged in
                    Log.e(TAG,"Logged in");
                    Profile userProfile = Profile.getCurrentProfile();
                    Log.e(TAG,userProfile.getName());
                }
            }, SPLASH_TIME_OUT);
        } else {
            new Handler().postDelayed(new Runnable() {

                @Override
                public void run() {
                    //User is logged out now!! Handle in your way
                    Log.e(TAG,"Logged out");
                }
            }, SPLASH_TIME_OUT);
        }
    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        //This line below is really necessary
        callbackManager.onActivityResult(requestCode, resultCode, data);
    }
    
    ... //Other Methods
}