Реализация кнопки входа в Facebook Sdk 4 android

Итак, я пытаюсь реализовать кнопку входа в систему, используя Fragment. Документация на сайте facebook немного сбивает с толку. Мое приложение вылетает даже при запуске. Ошибки в сборке нет. Вот мой код.. Если кто-то может мне помочь, я был бы признателен!!

MainActivity.java:

public class MainActivity extends FragmentActivity {


    private CallbackManager callbackManager;
   // private Fragment mainfrag=new Fragment();
    private AccessTokenTracker accessTokenTracker;
    private boolean isResumed = false;


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


        FacebookSdk.sdkInitialize(getApplicationContext());
        callbackManager = CallbackManager.Factory.create();
        accessTokenTracker = new AccessTokenTracker() {
           @Override
            protected void onCurrentAccessTokenChanged(AccessToken oldAccessToken, AccessToken currentAccessToken) {

            }
        };

        setContentView(R.layout.activity_main);
 }

activity_main.xml:

<LinearLayout 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:background="@drawable/bg"
android:orientation="vertical"
android:weightSum="1">

<ImageView
    android:layout_width="300dp"
    android:layout_height="100dp"
    android:layout_gravity="center"
    android:src="@drawable/banner" />

<fragment
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:name="com.moviere.MainFragment"
    android:id="@+id/fragment"
    android:layout_gravity="center_horizontal"
    android:layout_weight="0.17" />

fragment_main.xml:

<FrameLayout 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" tools:context="com.moviere.MainFragment">


<TextView android:layout_width="match_parent" android:layout_height="match_parent"
    android:text="@string/hello_blank_fragment"
    android:gravity="center_horizontal" />

<com.facebook.widget.LoginButton
    android:id="@+id/login_button"
    android:layout_width="250dp"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal|top"
    android:layout_marginTop="30dp" />

and at last MainFragment.java:

public class MainFragment extends Fragment {

private CallbackManager callbackManager;
private LoginButton loginButton;

public MainFragment() {
    // Required empty public constructor
}

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

    loginButton = (LoginButton) view.findViewById(R.id.login_button);
    loginButton.setReadPermissions("user_friends");
    // If using in a fragment
    loginButton.setFragment(this);
    // Other app specific specialization
// Callback registration
    loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {
            Toast.makeText(getActivity(),"Success",Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onCancel() {
            Toast.makeText(getActivity(),"fail",Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onError(FacebookException exception) {
            Toast.makeText(getActivity(),"error", Toast.LENGTH_SHORT).show();
        }
    });
    return view;
}

Изменить: Android Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.moviere" >
<uses-permission android:name="android.permission.INTERNET"/>
<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <meta-data android:name="com.facebook.sdk.ApplicationId" android:value="@string/facebook_app_id"/>
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name="com.facebook.FacebookActivity"
        android:configChanges=
            "keyboard|keyboardHidden|screenLayout|screenSize|orientation"
        android:theme="@android:style/Theme.Translucent.NoTitleBar"
        android:label="@string/app_name" />
</application>