In ViewPager of Fragments, fragments cannot flip like cards

Introduction

I am creating an application that has a start menu with multiple images / slices. I want every image I click to animate to flip the map and change it to another image (which has some ImageButtons that lead you to the main application)

Problem

I tried to implement animation by following this but whenever I click on the image / fragment there is a problem which after doing a little research on the internet I found out about it from trying to do an action for fragments on the android.support.v4.app file. Fragments in logcat file:

java.lang.RuntimeException: Unknown animation name: objectAnimator

Main activity class

public class MainMenuActivity extends FragmentActivity {
/**
 * the pager which handles animation and lets up swipe horizontally to access previous and next memo game
 */
ViewPager viewPager;

/**
 * the pager adapter which provides the pages to the pager widget
 */
PagerAdapter adapter;

/**
 * probably useless but we'll see in the future
 */
int[] game;

/**
 * the number of the memo games provided in the version
 */
public static final int NUM_OF_GAMES=8;
/**
 * the number of the position where the pager is
 */
public static int POSITION;
public Context context;
/**
 * whether or not we're showing the back of the card (otherwise showing the front)
 */
private boolean mShowingBack = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    //remove the title
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    super.onCreate(savedInstanceState);
    //making the window full screen
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.activity_main_menu);

    context=this.getApplicationContext();

    viewPager=(ViewPager)findViewById(R.id.pager);
    adapter = new MemoGameFragmentPagerAdapter(getSupportFragmentManager());
    viewPager.setAdapter(adapter);

    viewPager.setOffscreenPageLimit(6);
    viewPager.setPageMargin(20);
}

private class MemoGameFragmentPagerAdapter extends FragmentStatePagerAdapter{
    public MemoGameFragmentPagerAdapter(android.support.v4.app.FragmentManager fm){
        super(fm);
    }

    @Override
    public Fragment getItem(int position){
        MainMenuActivity.POSITION=position;
        return new MemoFrontFragment();
    }

    @Override
    public int getCount(){
        return NUM_OF_GAMES;
    }

    @Override
    public float getPageWidth(int position){
        return (0.4f);
    }
}


public void flipMemoGame(){
    //the card is on its back side
    if(mShowingBack){
        android.support.v4.app.FragmentManager fm =getSupportFragmentManager();
        fm.popBackStack();
        return;
    }

    //the card is on its front side
    mShowingBack=true;
    getSupportFragmentManager().beginTransaction().setCustomAnimations(R.animator.card_flip_right_in,
            R.animator.card_flip_right_out,
            R.animator.card_flip_left_in,R.animator.card_flip_left_out)
            .replace(R.id.pager,new MemoBackFragment()).addToBackStack(null).commit();
}

public void setOnClickListeners(View v){
    ImageView img;
    img=(ImageView)v;
    img.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            flipMemoGame();
        }
    });
}}

      

        
        
        
      

    

Java Snippet File

public class MemoFrontFragment extends Fragment {

static ImageView IMAGE;
int[] game;
int position=MainMenuActivity.POSITION;
ImageView img;
View view;

@Override
public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState){

    game = new int[]{R.drawable.img,R.drawable.img0,R.drawable.img1,R.drawable.img2,R.drawable.img3,R.drawable.img4,R.drawable.img6,R.drawable.img7};

        view=inflater.inflate(R.layout.fragment_memo_front_game_1,container,false);
    img=(ImageView)view.findViewById(R.id.united_states_flag);
    img.setImageResource(game[position]);
    IMAGE=img;
    return view;
}
}

      

        
        
        
      

    

Another snippet file

public class MemoBackFragment extends Fragment {
    View view;

    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState){
        view=inflater.inflate(R.layout.fragment_memo_back_game_1,container,false);
        return view;
    }
}

      

        
        
        
      

    

If you need anything else, let me know and I will provide it as soon as possible.