IssueTracker

Sample project https://drive.google.com/open?id=0B6SE3dTgd8NPSGFTMkg0dDd5dFU

I'm going to leave this here as well, for reference: http://stackoverflow.com/questions/40171801/bottomnavigationview-hides-when-scrolling-up-instead-of-down

In my use case, the BottomNavigationView is inside a fragment, inside a FrameLayout which is contained in a CoordinatorLayout and the scroll to hide technique works, but in reverse compared to how it's supposed to work. Using the BottomNavigationView directly inside the CoordinatorLayout doesn't have any scroll behavior though.

I'm having the same issue. There is an estimation when this issue will be fixed?

This has been released in support library 25.0.1.

Scroll behavior is still missing. For those that are looking for one, sample project archive contains it.

Elevation part was fixed. Still working on the behavior.

Elevation is broken if you use app:itemBackground rather than android:background since it's setting the elevation on itself rather than mMenuView. Why is itemBackground exposed? Should I not just use android:background?

[Comment deleted]

Set transparent color for app:itemBackground and use solid color on the BottomNavigationView background. That would be the only way to see the elevation, otherwise the top most parent (BNV) will not draw the elevation onto which you are applying elevation, since it doesnt have solid background.  

If android:background is used on < 21, shadow is overlaid over the background. Elevation does not cast upward shadow, does it? So the method addCompatibilityTopDivider() in current 25.0.1 should be available for all versions.

app:itemBackground is meant to be used for adding ripples/pressed state. By default it just has a round ripple. To set the background color for you should use android:background, once you do so you will see the shadow on API 21+ above BottomNavigationView (just using elevation) and for pre API 21 we add a simple 1dp divider to separate it from the background as elevation does not exist in these platforms.

Am I missing something?

You can't cast shadow to the top. I tried to add android:elevation="40dp" and         android:elevation="8dp" on a solid background but still I was unable to see the shadow cast on the top, shadow is cast only below the BNV (this is perfectly normal). Given this, I said that top divider should be available for all version to achieve top shadow.

I was just confused by what app:itemBackground was for, but that makes sense. thanks!

When is the scrolling behavior planned to be released?

I have updated to the new Support Library version (25.1.0) and I still see no shadow above the BNV, see attached screenshot.

    <android.support.design.widget.BottomNavigationView
        android:elevation="40dp"
        android:id="@+id/bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="@color/darkestGray"
        app:itemIconTint="@drawable/nav_item_color_state"
        app:itemTextColor="@drawable/nav_item_color_state"
        app:menu="@menu/bottom_navigation_widget" />

Updated to 25.1.0. Shadow doesn't displayed.

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="@color/colorPrimary"
        android:elevation="8dp"
        app:elevation="8dp"
        app:itemIconTint="@drawable/bottom_nav_color_state"
        app:itemTextColor="@drawable/bottom_nav_color_state"
        app:menu="@menu/bottom_navigation_main"/>

is the shadow and scrolling behavior has been added?

wait for shadow and scrolling behavior...

The target release was 25.0.1 and we're now at 26.0.0-beta2. Could you guys at least put an actual, realistic target on this issue?

Scrolling behavior with CoordinatorLayout has been implemented, and should be available in the next release.

Passing bug to Avigail to comment about bottom nav elevation behavior.

I could not find any info about this, is this released ?

Any news on when this will be released?

I'm revisiting a project with this issue and this is still not fixed on v27.1.1. If I have a BottomNavigationView inside a parent CoordinatorLayout, it doesn't scroll. It works though perfectly when manually setting translationY:

appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
    @Override
    public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
        bottomNavigationView.setTranslationY(verticalOffset*-1);
    }
});

However, when trying the same technique, while having the BottomNavigationView inside a FrameLayout, which itself is the child of the parent CoordinatorLayout, the BottomNavigationView doesn't even show up in the UI.
Trying the same AppBarLayout OffsetChangedListener on a different UI component (such as a FAB), while inside the FrameLayout, works just as if the FAB was a direct child of the CoordinatorLayout.

So what's the difference between the 2 setups? Why does the FAB work, but not the BottomNavigationView?
Also, where's the scrolling behavior that was about to be released?

Scrolling behavior has been added. You can use it by setting a HideBottomViewOnScrollBehavior on the BottomNavigationView: app:layout_behavior="@string/hide_bottom_view_on_scroll_behavior".

See class documentation for BottomNavigationView: https://developer.android.com/reference/com/google/android/material/bottomnavigation/BottomNavigationView.

And for HideBottomViewOnScrollBehavior: https://developer.android.com/reference/com/google/android/material/behavior/HideBottomViewOnScrollBehavior.

This is available in our 28.0.0-alpha1 release or the 1.0.0-alpha1 release or later.

When the bottom bar is partly visible (eg user scrolled just a bit and stopped scrolling), does the bottom bar snaps automatically to either be fully visible or hidden like
a CollapsingToolbarLayout would do with  app:layout_scrollFlags="scroll|snap"  ?

Im on 28.0.0 and the bottom shadow still doesnt show up at the top when i set the app:elevation in BNV.

is it yet to be fixed ? Here is my layout

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/landing_bottom_nav"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:background="@color/white"
        app:elevation="4dp"
        android:elevation="4dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:menu="@menu/landing_menu"/>

With this HideBottomViewOnScrollBehavior , Scrolling behavior working fine but, Showing white space occupying the size of that bottom view.