Programmatically show BottomNavigationView in CoordinatorLayout when it's hidden in another fragment

Question

Im using bottom navigation view with hide_bottom_view_on_scroll_behavior. When user selects item from first fragment list app goes to detail fragment.I want to show bottom navigation view if its hidden in that (detail) fragment.

Main activity xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.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"
android:fitsSystemWindows="true"
tools:actionBarNavMode="standard"
tools:context=".MainActivity">

<com.google.android.material.appbar.AppBarLayout
    android:id="@+id/app_bar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay"
    app:elevation="0dp">

    <com.google.android.material.appbar.CollapsingToolbarLayout
        android:id="@+id/toolbar_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        app:contentScrim="?attr/colorPrimary"
        app:layout_scrollFlags="scroll|exitUntilCollapsed">
        <!--app:layout_scrollFlags="scroll|exitUntilCollapsed"-->
        <!--app:layout_scrollFlags="scroll|enterAlways|snap"-->

        <ImageView
            android:id="@+id/expandedImage"
            android:layout_width="match_parent"
            android:layout_height="200dp"
            android:scaleType="centerCrop"
            android:src="@drawable/hrt1"
            android:visibility="gone"
            app:layout_collapseMode="parallax"
            app:layout_collapseParallaxMultiplier="0.7" />

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:layout_collapseMode="pin"
            app:layout_scrollFlags="scroll|enterAlways|snap" />
    </com.google.android.material.appbar.CollapsingToolbarLayout>
</com.google.android.material.appbar.AppBarLayout>

<com.aero51.moviedatabase.ui.CustomViewPager
    android:id="@+id/view_pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:isScrollContainer="true"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

<com.google.android.material.bottomnavigation.BottomNavigationView
    android:id="@+id/bottom_navigation"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom"
    android:background="@color/colorPrimary"
    app:itemBackground="@color/colorPrimary"
    app:itemIconTint="@drawable/bottom_navigation_color_selector"
    app:itemTextColor="@drawable/bottom_navigation_color_selector"
    app:layout_behavior="@string/hide_bottom_view_on_scroll_behavior"
    app:menu="@menu/menu_bottom_navigation" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

I tried with following code in my detail fragment onCreateView but it doesnt work:

   bottomNavigationView = (BottomNavigationView) getActivity().findViewById(R.id.bottom_navigation);
   bottomNavigationView.setVisibility(View.VISIBLE);
   bottomNavigationView.animate().alpha(1f).setDuration(1000).start();

Help appreciated

Answer 1

To show the BottomNavigationView you need to inflate the behavior as below:

And then call slideDown() to hide or slideUp to show the BottomNavigationView

BottomNavigationView bottomNavigationView = (BottomNavigationView) getActivity().findViewById(R.id.bottom_navigation);
ViewGroup.LayoutParams layoutParams = bottomNavigationView.getLayoutParams();
if (layoutParams instanceof CoordinatorLayout.LayoutParams) {
    CoordinatorLayout.Behavior behavior =
            ((CoordinatorLayout.LayoutParams) layoutParams).getBehavior();
    if (behavior instanceof HideBottomViewOnScrollBehavior) {
        HideBottomViewOnScrollBehavior<BottomNavigationView> hideShowBehavior =
                (HideBottomViewOnScrollBehavior<BottomNavigationView>) behavior;
        hideShowBehavior.slideUp(bottomNavigationView);
    }
}