Bottom Navigation View gets Shrink Down

Question

I have made an app with bottom navigation view with Promo, Store, Reward, Coupon and Account tabs when I am changing from Coupon fragment to any other fragment, the bottom navigation view gets shrunk down as shown in the image, I tried changing layout width, height and converting coordinator layout to linear layout but it didn't help. The problem is occurring when I'm switching from home to any other tab only.

Layout File activity_main.xml

<android.support.constraint.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activity.MainActivity">

<FrameLayout
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginBottom="56dp"
    android:text="@string/title_home"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="0dp"
    android:layout_marginStart="0dp"
    android:background="@color/white"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:itemTextColor="@color/selector_bottom_navigation"
    app:itemIconTint="@color/selector_bottom_navigation"
    app:menu="@menu/navigation" />

Java File MainActivity.java

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

    //loading the default fragment
    loadFragment(new PromoFragment());

    //getting bottom navigation view and attaching the listener
    BottomNavigationView navigation = findViewById(R.id.navigation);
    BottomNavigationViewUtils.disableShiftMode(navigation);
    navigation.setOnNavigationItemSelectedListener(this);
}

@Override
public boolean onCreatePanelMenu(int featureId, Menu menu) {
    getMenuInflater().inflate(R.menu.menu_wallet, menu);
    return super.onCreatePanelMenu(featureId, menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle item selection
    switch (item.getItemId()) {
        case R.id.menu_wallet1:
            return true;
        case R.id.menu_qrcode:
            Intent intent = new Intent(this, ScannerActivity.class);
            startActivity(intent);
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
    Fragment fragment = null;

    switch (item.getItemId()) {
        case R.id.navigation_promo:
            fragment = new PromoFragment();
            break;

        case R.id.navigation_store:
            fragment = new StoreFragment();
            break;

        case R.id.navigation_reward:
            fragment = new RewardFragment();
            break;

        case R.id.navigation_coupon:
            fragment = new CouponFragment();
            break;

        case R.id.navigation_account:
            fragment = new AccountFragment();
            break;
    }

    return loadFragment(fragment);
}

private boolean loadFragment(Fragment fragment) {
    if (fragment != null) {
        getSupportFragmentManager()
                .beginTransaction()
                .replace(R.id.fragment_container, fragment)
                .commit();
        return true;
    }
    return false;
}

This is the picture I meant:

I previously added SearchView to the coupon fragment and fragment store

Answer 1

It turns out that if you are using a coordinator layout and viewpager inside a fragment, you will notice that the viewpager extends the screen a bit. Just disable the scroll features of the coordinator layout inside the fragment and you will notice the bottom bar doesn't get shrunk. Weird I know, but it works.