Background color animation not working with setOnTabSelectedListener

[AliRezaBeitari]

This is my code:

import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.view.ViewPager;
import android.support.v4.view.animation.LinearOutSlowInInterpolator;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.app.AppCompatDelegate;
import android.view.View;
import android.view.animation.OvershootInterpolator;
import android.widget.Toast;

import com.aurelhubert.ahbottomnavigation.AHBottomNavigation;
import com.aurelhubert.ahbottomnavigation.AHBottomNavigationItem;
import com.aurelhubert.ahbottomnavigation.AHBottomNavigationViewPager;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity implements PageFragment.OnFragmentInteractionListener {

    private MainViewPagerAdapter adapter;
    private ArrayList<AHBottomNavigationItem> bottomNavigationItems = new ArrayList<>();

    // UI
    private AHBottomNavigationViewPager viewPager;
    private AHBottomNavigation bottomNavigation;
    private FloatingActionButton floatingActionButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);

        initUI();
    }

    /**
     * Init UI
     */
    private void initUI() {

        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
            AppCompatDelegate.setCompatVectorFromResourcesEnabled(true);
        }

        bottomNavigation = findViewById(R.id.bottom_navigation);

        viewPager = findViewById(R.id.view_pager);
        viewPager.setPagingEnabled(true);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            }

            @Override
            public void onPageSelected(int position) {
                bottomNavigation.setCurrentItem(position);
                animateFloatingButton(position);
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
        floatingActionButton = findViewById(R.id.floating_action_button);

        AHBottomNavigationItem item1 = new AHBottomNavigationItem(R.string.tab_1, R.drawable.ic_apps_black_24dp, R.color.color_tab_1);
        AHBottomNavigationItem item2 = new AHBottomNavigationItem(R.string.tab_2, R.drawable.ic_maps_local_bar, R.color.color_tab_2);
        AHBottomNavigationItem item3 = new AHBottomNavigationItem(R.string.tab_3, R.drawable.ic_maps_local_restaurant, R.color.color_tab_3);

        bottomNavigationItems.add(item1);
        bottomNavigationItems.add(item2);
        bottomNavigationItems.add(item3);

        bottomNavigation.addItems(bottomNavigationItems);

        bottomNavigation.setColored(true);
        bottomNavigation.setSelectedBackgroundVisible(true);

        bottomNavigation.manageFloatingActionButtonBehavior(floatingActionButton);
        bottomNavigation.setTranslucentNavigationEnabled(true);

        bottomNavigation.setOnTabSelectedListener(new AHBottomNavigation.OnTabSelectedListener() {
            @Override
            public boolean onTabSelected(int position, boolean wasSelected) {
                if (wasSelected) {
                    return true;
                }

                viewPager.setCurrentItem(position);

                animateFloatingButton(position);

                return true;
            }
        });

        viewPager.setOffscreenPageLimit(3);
        adapter = new MainViewPagerAdapter(getSupportFragmentManager());
        viewPager.setAdapter(adapter);

        bottomNavigation.setCurrentItem(1);
    }

    @Override
    public void onFragmentInteraction(Uri uri) {

    }

    void animateFloatingButton(int position) {
        if (position == 1) {
            floatingActionButton.setVisibility(View.VISIBLE);
            floatingActionButton.setAlpha(0f);
            floatingActionButton.setScaleX(0f);
            floatingActionButton.setScaleY(0f);
            floatingActionButton.animate()
                    .alpha(1)
                    .scaleX(1)
                    .scaleY(1)
                    .setDuration(300)
                    .setInterpolator(new OvershootInterpolator())
                    .setListener(new Animator.AnimatorListener() {
                        @Override
                        public void onAnimationStart(Animator animation) {

                        }

                        @Override
                        public void onAnimationEnd(Animator animation) {
                            floatingActionButton.animate()
                                    .setInterpolator(new LinearOutSlowInInterpolator())
                                    .start();
                        }

                        @Override
                        public void onAnimationCancel(Animator animation) {

                        }

                        @Override
                        public void onAnimationRepeat(Animator animation) {

                        }
                    })
                    .start();

        } else {
            if (floatingActionButton.getVisibility() == View.VISIBLE) {
                floatingActionButton.animate()
                        .alpha(0)
                        .scaleX(0)
                        .scaleY(0)
                        .setDuration(300)
                        .setInterpolator(new LinearOutSlowInInterpolator())
                        .setListener(new Animator.AnimatorListener() {
                            @Override
                            public void onAnimationStart(Animator animation) {

                            }

                            @Override
                            public void onAnimationEnd(Animator animation) {
                                floatingActionButton.setVisibility(View.GONE);
                            }

                            @Override
                            public void onAnimationCancel(Animator animation) {
                                floatingActionButton.setVisibility(View.GONE);
                            }

                            @Override
                            public void onAnimationRepeat(Animator animation) {

                            }
                        })
                        .start();
            }
        }
    }
}

When I slide the view pager, background color animation will be triggered; but when I click on each tab it won't!! Where is the problem?!

Thanks!