Android ผมลองเขียนปุ่ม login facebook แล้วมันขึ้น error รบกวนช่วยแนะนำหน่อยว่ามต้องแก้ไขตรงไหน

package com.example.firstlogin;

import android.content.Intent;
import android.os.*;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

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

public class MainActivity extends ActionBarActivity {

    private static String TAG = MainActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        
        if (savedInstanceState == null) {
            getSupportFragmentManager()
            	.beginTransaction()
                .add(R.id.facebookLoginButton, new PlaceholderFragment())
                .commit();
        } 
        
        
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        private UiLifecycleHelper uiHelper;
        private Session.StatusCallback callback = new Session.StatusCallback() {
            @Override
            public void call(Session session, SessionState state, Exception exception) {
                onSessionStateChange(session, state, exception);
            }
        };

        public PlaceholderFragment() {
        }

        private void onSessionStateChange(Session session, SessionState state, Exception exception) {
            if (state.isOpened()) {

                Request request = Request.newMeRequest(session, new GraphUserCallback() {

                    @Override
                    public void onCompleted(GraphUser user, Response response) {
                        Toast.makeText(getActivity(), 
                                "Hello " + user.getName(), 
                                Toast.LENGTH_LONG).show();
                    }
                });
                request.executeAsync();

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

        @Override
        public void onResume() {
            super.onResume();

            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);
        }

        @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 rootView = inflater.inflate(R.layout.activity_main, container,
                    false);

            LoginButton authButton = (LoginButton) rootView.findViewById(R.id.facebookLoginButton);
            authButton.setFragment(this);
            return rootView;
        }

    }

}