This is my first time working with fragments. I'm implementing a facebook login. When I add the piece of code for the fragment

```
            /* FACEBOOK FRAGMENT SETUP */
            if (savedInstanceState == null) {
                // Add the fragment on initial activity setup
                mainFragment = new MainFragment();
                getSupportFragmentManager()
                .beginTransaction()
                .add(android.R.id.content, mainFragment)
                .commit();
            } else {
                // Or set the fragment from restored state info
                mainFragment = (MainFragment) getSupportFragmentManager()
                .findFragmentById(android.R.id.content);
            }

```

then none of the onClickListeners for my buttons or text views work. I'm not sure why this is happening. Can anyone shed light on this?

Main Activity Code

```
public class ActivityLogin extends FragmentActivity {
     // label to display gcm messages
    TextView lblMessage;

    // Asyntask
    AsyncTask<Void, Void, Void> mRegisterTask;

    private EditText edt_username, edt_password;
    public String gcm_id, un, pw, tab;
    public ProgressDialog pdialog;
    static int count = 0;
    public String gcm_regid;

    ConnectionDetector cd;
    AlertDialogManager alert = new AlertDialogManager();
    SharedPreferences sp1;
    GPSTracker gpstracker;

    RequestQueue queue;

    //FB FRAGMENT
    private MainFragment mainFragment;

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

        Intent in = getIntent();
        tab = in.getStringExtra("tab");
        queue = Volley.newRequestQueue(this);

        //Check for saved credentials.
        sp1=getSharedPreferences("Login",MODE_PRIVATE);
        un = sp1.getString("un", "");
        pw = sp1.getString("pw", "");

        // Make sure the device has the proper dependencies.
        GCMRegistrar.checkDevice(this);
        gpstracker = new GPSTracker(getApplicationContext());

        // Make sure the manifest was properly set - comment out this line
        // while developing the app, then uncomment it when it's ready.
        //GCMRegistrar.checkManifest(this);

        cd = new ConnectionDetector(getApplicationContext());

        //registerReceiver(mHandleMessageReceiver, new IntentFilter(DISPLAY_MESSAGE_ACTION));
        final String regId = GCMRegistrar.getRegistrationId(this);

        // Check if regid already presents
        if (regId.equals("")) {
            // Registration is not present, register now with GCM           
            GCMRegistrar.register(this, SENDER_ID);
            gcm_id=GCMRegistrar.getRegistrationId(this);
        } else {
            gcm_id=regId;
            // Device is already registered on GCM
            if (GCMRegistrar.isRegisteredOnServer(this)) {
                // Skips registration.              
                Toast.makeText(getApplicationContext(), "Already registered with GCM", Toast.LENGTH_LONG).show();
            }
        }

        /*if(un==""){*/
            setContentView(R.layout.login_layout);

            Button login = (Button) findViewById(R.id.btn_login);
            /* init EditText */
            edt_username = (EditText) findViewById(R.id.edt_userNameLogin);
            edt_password = (EditText) findViewById(R.id.edt_PasswordLogin);

            login.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {

                    if (edt_username.getText().toString().equalsIgnoreCase("")) {

                        alert.showAlertDialog(ActivityLogin.this, "KpFun alert!",
                                "Username no empty!", false);
                        edt_username.requestFocus();
                        return;
                    }
                    if (edt_password.getText().toString().equalsIgnoreCase("")) {
                        alert.showAlertDialog(ActivityLogin.this, "KpFun alert!",
                                "Password no empty!", false);
                        edt_password.requestFocus();
                        return;
                    }
                    if (!cd.isConnectingToInternet()) {
                        alert.showAlertDialog(ActivityLogin.this, "KpFun alert!",
                                "No network, Please check your data connection!",
                                false);
                        return;
                    }

                    Login();

                }
            });

            TextView backLink = (TextView) findViewById(R.id.tv_Back);
            backLink.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    Intent inRegister = new Intent(ActivityLogin.this,
                            SplashScreen.class);
                    startActivity(inRegister);
                    finish();

                }
            });

        /*}else{
            Login();

        }*/

             /* FACEBOOK FRAGMENT SETUP */
            if (savedInstanceState == null) {
                // Add the fragment on initial activity setup
                mainFragment = new MainFragment();
                getSupportFragmentManager()
                .beginTransaction()
                .add(android.R.id.content, mainFragment)
                .commit();
            } else {
                // Or set the fragment from restored state info
                mainFragment = (MainFragment) getSupportFragmentManager()
                .findFragmentById(android.R.id.content);
            }

            if(!un.equals("")){
                Login();
            }

    }
    /* MORE STUFF TAKEN OUT */

```

FRAGMENT CODE

```
package com.kpfunusa1;

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

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.Response;
import com.facebook.Request;
import com.facebook.Session;
import com.facebook.SessionState;
import com.facebook.UiLifecycleHelper;
import com.facebook.model.GraphUser;
import com.facebook.widget.LoginButton;

public class MainFragment extends Fragment {
    private static final String TAG = "MainFragment";
    private UiLifecycleHelper uiHelper;

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

    }

    @Override
    public View onCreateView(LayoutInflater inflater, 
            ViewGroup container, 
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.login_layout, container, false);

        LoginButton authButton = (LoginButton) view.findViewById(R.id.authButton);
        authButton.setFragment(this);
        authButton.setReadPermissions(Arrays.asList("public_profile", "email", "user_friends", "user_birthday", "user_location", "user_website", "user_likes", "user_status"));

        return view;
    }

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

    private void onSessionStateChange(Session session, SessionState state, Exception exception) 
     {
        if (state.isOpened()) 
        {
            Log.i("facebook", "Logged in...");
            Request.newMeRequest(session, new Request.GraphUserCallback() 
            {

                @Override
                public void onCompleted(GraphUser user, Response response) 
                {

                    if(user!=null)
                    {
                      String test=user.getName();
                      test =user.getProperty("email")+"";
                      test=(user.getProperty("gender")+"");
                      test=(user.getId()+"");
                      test=user.getBirthday();
                      test=user.getUsername();
                      test=user.getId();
                    }
                    else
                    {
                        String test=("its null");
                        test=(response.getError().getErrorMessage());
                    }
                }
            }).executeAsync();

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

    @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);
    }

}

```