MainFragment.java

package jaangari.opensoft.iitkgp.jaankari;

import android.content.Intent;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.Signature;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Base64;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.facebook.Session;
import com.facebook.SessionState;
import com.facebook.UiLifecycleHelper;
import com.facebook.widget.LoginButton;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import jaangari.opensoft.iitkgp.jaangari.R;

/**
 * Created by rahulanishetty on 20/01/15.
 */
public class MainFragment extends Fragment {

    private static final String TAG = "MainFragment";
    private UiLifecycleHelper uiHelper;

    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.activity_login, container, false);
        LoginButton authButton = (LoginButton) view.findViewById(R.id.authButton);
        authButton.setReadPermissions(Arrays.asList("public_profile"));
        authButton.setFragment(this);
        return view;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        uiHelper = new UiLifecycleHelper(getActivity(), callback);
        uiHelper.onCreate(savedInstanceState);
    }

    @Override
    public void onResume() {
        super.onResume();
        // For scenarios where the main activity is launched and user
        // session is not null, the session state change notification
        // may not be triggered. Trigger it if it's open/closed.
        Session session = Session.getActiveSession();
        if (session != null &&
                (session.isOpened() || session.isClosed()) ) {
            onSessionStateChange(session, session.getState(), null);
        }
        uiHelper.onResume();
    }

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

    @Override
    public void onPause() {
        super.onPause();
        uiHelper.onPause();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        uiHelper.onDestroy();
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        uiHelper.onSaveInstanceState(outState);
    }

    private void onSessionStateChange(Session session, SessionState state, Exception exception) {
        // TODO When the session state is open, you can display your authenticated UI, such as making a new button visible.
        // When the state is closed, you can display the non-authenticated UI, such as hiding the new button.

        if (state.isOpened()) {
            Log.i(TAG, "Logged in...");
        } else if (state.isClosed()) {
            Log.i(TAG, "Logged out...");
        }
    }

    private Session.StatusCallback callback = new Session.StatusCallback() {
        @Override
        public void call(Session session, SessionState state, Exception exception) {
            onSessionStateChange(session, state, exception);
        }
    };
}