How to hide bottom nav bar in fragment

Question

I have bottom nav bar define in the Main activity. I have three fragments linked with BottomNavigation bar in fragments I have recycler view so I want to hide BottomNavigation bar when RecyclerView scrolls down and shows when RecyclerView scrolls up. My problem is how can I access BottomNavigation bar in fragments because it is defined in MainActivity.

This is my code:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<android.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay"
    app:elevation="0dp"
    android:background="@color/colorPrimary"
    android:paddingBottom="7dp"
    android:fitsSystemWindows="true">


    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:popupTheme="@style/AppTheme.PopupOverlay"
        app:layout_scrollFlags="scroll|enterAlways|snap">

        <Spinner
            android:layout_width="110dp"
            android:layout_height="50dp"
            android:id="@+id/chooseLocation"
            app:backgroundTint="@android:color/white"/>

    </android.support.v7.widget.Toolbar>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:layout_marginLeft="16dp"
        android:layout_marginRight="16dp"
        android:id="@+id/search"
        android:paddingTop="6dp"
        android:paddingBottom="6dp"
        android:paddingRight="6dp"
        android:paddingLeft="12dp"
        android:hint="Search here"
        android:textColorHint="#9e9e9e"
        android:textColor="#000"
        tools:ignore="HardcodedText"
        android:background="@drawable/search_edit_text"
        android:paddingEnd="6dp"
        android:paddingStart="12dp"/>

</android.support.design.widget.AppBarLayout>

<include layout="@layout/content_main" />

<android.support.design.widget.BottomNavigationView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/bottomBar"
    android:layout_gravity="bottom"
    app:menu="@menu/bottom_menu"
    android:background="#fff"
    app:itemIconTint="@drawable/nav_check"
    app:itemTextColor="@drawable/nav_check"/>

</android.support.design.widget.CoordinatorLayout>

fragment_home.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
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=".Tab1Fragment"
android:background="#fff">

<android.support.v7.widget.RecyclerView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/purchasedBook"/>


</RelativeLayout>

This is how my fragments are defined as there is no bottom nav bar in any fragments so how can I access bottom nav bar in fragments.

Someone, please let me know any help would be appreciated.

THANKS

Answer 1

To access your BottomNavigationView from within the fragments use the following code:

BottomNavigationView navBar = getActivity().findViewById(R.id.bottomBar);

Answer 2

navController.addOnDestinationChangedListener { _, destination, _ ->
   if(destination.id == R.id.full_screen_destination) {
       
       bottomNavigationView.visibility = View.GONE
   } else {
       
       bottomNavigationView.visibility = View.VISIBLE
   }
}

Do this in the main activity. Here R.id.full_screen_destination is id of the fragment in navigation fragment.

Answer 3

As the fragment is always inside an activity and you can call getActivity() in fragment to access objects that already exist in the activity. So you can do this:

Activity

public class MainActivity extends Activity {
//...
   Toolbar toolbar;
//...
   public Toolbar getNav() {
      return toolbar;
   }
//...
}

Fragment

//...
if(getActivity() != null && getActivity instanceOf MainActivity)
    ((MainActivity)getActivity()).getNav().setVisiblity(View.GONE);
//...

Answer 4

Try this,

Add this line in the BottomNavigationView in Xml

app:layout_behavior="@string/hide_bottom_view_on_scroll_behavior"

And Implement this BottomNavigation behavior using CoOrdinator Layout and you can hide or show the view using the scroll listeners.

public class BottomNavigationViewBehavior extends CoordinatorLayout.Behavior<BottomNavigationView> {

private int height;

@Override
public boolean onLayoutChild(CoordinatorLayout parent, BottomNavigationView child, int layoutDirection) {
    height = child.getHeight();
    return super.onLayoutChild(parent, child, layoutDirection);
}

@Override
public boolean onStartNestedScroll(@NonNull CoordinatorLayout coordinatorLayout,
                               BottomNavigationView child, @NonNull 
                               View directTargetChild, @NonNull View target,
                               int axes, int type)
{
    return axes == ViewCompat.SCROLL_AXIS_VERTICAL;
}

@Override
public void onNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull BottomNavigationView child,
           @NonNull View target, int dxConsumed, int dyConsumed,
           int dxUnconsumed, int dyUnconsumed, 
            @ViewCompat.NestedScrollType int type)
{
   if (dyConsumed > 0) {
       slideDown(child);
   } else if (dyConsumed < 0) {
       slideUp(child);
   }
}

private void slideUp(BottomNavigationView child) {
    child.clearAnimation();
    child.animate().translationY(0).setDuration(200);
}

private void slideDown(BottomNavigationView child) {
    child.clearAnimation();
    child.animate().translationY(height).setDuration(200);
}

}

Add this line code to your Activity where it contains bottom navigation

bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_nav);
CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) 
bottomNavigationView .getLayoutParams();
layoutParams.setBehavior(new BottomNavigationViewBehavior());

Try this and let me know Digvijay.Happy Coding.