How to scroll up/down of bottom bar on scrolling of RecyclerView

Question

With Google’s recent release of the Design Support Library several cool new views have been introduced. Using some of the new components (e.g. CoordinatorLayout ) might (!) enable you to achieve the scrolling behavior.

I was tryed with some built in scrolling behavior but nothing is working for me,

I have a bottombar(LinearLayout) in my layout in place of FloatingActionButton

Here what I want.

1. OnLaunch of this screen bottom bar should appear.
2. On scrollup of recyclerview bottom bar should scrolldown.
3. On scrolldown of recyclerview bottom bar should scrollup

Is there any builtin mechanism to achieve this ? or We need write java code?

Here is my code:

main_activty.xml

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

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

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:elevation="5dp"
            app:tabGravity="fill"
            app:tabIndicatorColor="@android:color/white"
            app:tabMode="fixed" />

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

    <!-- All Scrollable Views -->

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <!-- Bottom bar-->

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:background="#a0000000"
        android:orientation="horizontal"
        android:paddingBottom="@dimen/padding_small"
        android:paddingTop="@dimen/padding_small">

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.33"
            android:gravity="center"
            android:paddingBottom="@dimen/padding_small"
            android:paddingTop="@dimen/padding_small"
            android:text="AC"
            android:textColor="@color/white" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.33"
            android:gravity="center"
            android:paddingBottom="@dimen/padding_small"
            android:paddingTop="@dimen/padding_small"
            android:text="Sleeper"
            android:textColor="@color/white" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.33"
            android:gravity="center"
            android:paddingBottom="@dimen/padding_small"
            android:paddingTop="@dimen/padding_small"
            android:text="Premium"
            android:textColor="@color/white" />

    </LinearLayout>


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

fragment.xml (here I was putted my recyclerview code)

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:paddingBottom="@dimen/padding_small"
        android:paddingTop="@dimen/padding_small"
        android:weightSum="1">

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.33"
            android:background="@drawable/bg_srp_sorter"
            android:clickable="true"
            android:gravity="center"
            android:paddingBottom="@dimen/padding_small"
            android:paddingTop="@dimen/padding_small"
            android:text="Departure" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.33"
            android:background="@drawable/bg_srp_sorter"
            android:gravity="center"
            android:paddingBottom="@dimen/padding_small"
            android:paddingTop="@dimen/padding_small"
            android:text="Duration" />

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.33"
            android:gravity="center"
            android:paddingBottom="@dimen/padding_small"
            android:paddingTop="@dimen/padding_small"
            android:text="Price" />

    </LinearLayout>

    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/lite_gray"></View>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:weightSum="1">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/bus_list_recycler_view"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" />

    </LinearLayout>
</LinearLayout>

toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar 

xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorPrimary"
    app:layout_scrollFlags="scroll|enterAlways"
    android:minHeight="?attr/actionBarSize">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:weightSum="1">

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.10">

            <ImageView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:src="@drawable/abc_ic_ab_back_mtrl_am_alpha" />


        </LinearLayout>


        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.78"
            android:orientation="vertical">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:weightSum="1">

                <TextView
                    android:id="@+id/toolbar_title_source"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="0.47"
                    android:ellipsize="end"
                    android:singleLine="true"
                    android:text="Thiruvananthapuram "
                    android:textColor="@color/white"
                    android:textSize="@dimen/label_text_size_large" />

                <TextView
                    android:id="@+id/toolbar_title_arrow"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="0.08"
                    android:text="@string/char_right"
                    android:textColor="@color/white"
                    android:textSize="@dimen/label_text_size_large"
                    android:textStyle="bold" />

                <TextView
                    android:id="@+id/toolbar_title_destination"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="0.47"
                    android:ellipsize="end"
                    android:singleLine="true"
                    android:text=" Cochin"
                    android:textColor="@color/white"
                    android:textSize="@dimen/label_text_size_large" />


            </LinearLayout>


            <TextView
                android:id="@+id/toolbar_sub_title"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="2 Seat(s)"
                android:textColor="@color/lite_gray"
                android:textSize="@dimen/label_text_size_normal" />

        </LinearLayout>


        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.13">

            <ImageView
                android:layout_width="30dp"
                android:layout_height="30dp"
                android:scaleType="fitCenter"
                android:src="@drawable/filter" />
        </LinearLayout>
    </LinearLayout>

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

Obsess

Take a look at this answer #34027692 but don't extend default FAB behavior because you are not doing it for FAB. :) – Crosslet

Answer 1

since you are using CoordinatorLayout you could create a custom Behaviour that can achieve what you requested follow example below: create a class that extends CoordinatorLayout.Behavior<View> follow example below:

public class QuickReturnFloaterBehavior extends CoordinatorLayout.Behavior<View> {

    private int distance;

    public QuickReturnFloaterBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, View child, View directTargetChild, View target, int nestedScrollAxes) {
        return (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
    }

    @Override public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dx, int dy, int[] consumed) {
        if (dy > 0 && distance < 0 || dy < 0 && distance > 0) {
            child.animate().cancel();
            distance = 0;
        }
        distance += dy;
        final int height = child.getHeight() > 0 ? (child.getHeight()) : 600/*update this accordingly*/;
        if (distance > height && child.isShown()) {
            hide(child);
        } else if (distance < 0 && !child.isShown()) {
            show(child);
        }
    }

    private void hide(View view) {
        view.setVisibility(View.GONE);// use animate.translateY(height); instead
    }

    private void show(View view) {
        view.setVisibility(View.VISIBLE);// use animate.translateY(-height); instead
    }

}

now to apply this behaviour add this to your layout

app:layout_behavior="com.example.QuickReturnFloaterBehavior"

Libation

Answer 2

This how I did it:

mRecylerView.addOnScrollListener(new HideShowScrollListener() {
            @Override
            public void onHide() {
                //fab.animate().setInterpolator(new AccelerateDecelerateInterpolator()).scaleX(0).scaleY(0);
               // do your hiding animation here

            }

            @Override
            public void onShow() {
               // fab.animate().setInterpolator(new AccelerateDecelerateInterpolator()).scaleX(1).scaleY(1);
              // do your showing animation here
            }
        });

You will be needing HideShowScrollListener.class

/**
* This class is a ScrollListener for RecyclerView that allows to show/hide
* views when list is scrolled.
* */
public abstract class HideShowScrollListener extends RecyclerView.OnScrollListener {
    private static final int HIDE_THRESHOLD = 20;
    private int scrolledDistance = 0;
    private boolean controlsVisible = true;

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);

        if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) {
            onHide();
            controlsVisible = false;
            scrolledDistance = 0;
        } else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) {
            onShow();
            controlsVisible = true;
            scrolledDistance = 0;
        }

        if((controlsVisible && dy>0) || (!controlsVisible && dy<0)) {
            scrolledDistance += dy;
        }
    }

    public abstract void onHide();
    public abstract void onShow();

}

Mazuma

How about two different RecyclerView used?? – Eudora

Answer 3

Visibility and Hide with Animation in Your Fragment:

recyclerView.addOnScrollListener(new HideShowScrollListener() {
        final Fragment parentFragment = getParentFragment();
        @Override
        public void onHide() {
            bottomLayout.animate().setDuration(200).translationYBy(-bottomLayout.getHeight()).setListener(new AnimatorListenerAdapter() {
                    @Override
                    public void onAnimationEnd(Animator animation) {
                        bottomLayout.setVisibility(View.GONE);
                    }
            });
        }

        @Override
        public void onShow() {
            bottomLayout.animate().setDuration(200).translationY(0).setListener(new AnimatorListenerAdapter() {
                    @Override
                    public void onAnimationEnd(Animator animation) {
                        bottomLayout.setVisibility(View.VISIBLE);
                    }
            });
        }

        @Override
        public void onScrolled() {
            // To load more data
        }
    });

HideShowScrollListener.java

public abstract class HideShowScrollListener extends RecyclerView.OnScrollListener {
        private static final int HIDE_THRESHOLD = 20;
        private int scrolledDistance = 0;
        private boolean controlsVisible = true;

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

            onScrolled();

            if (scrolledDistance > HIDE_THRESHOLD && controlsVisible) {
                onHide();
                controlsVisible = false;
                scrolledDistance = 0;
            } else if (scrolledDistance < -HIDE_THRESHOLD && !controlsVisible) {
                onShow();
                controlsVisible = true;
                scrolledDistance = 0;
            }

            if((controlsVisible && dy>0) || (!controlsVisible && dy<0)) {
                scrolledDistance += dy;
            }
        }

        public abstract void onHide();
        public abstract void onShow();
        public abstract void onScrolled();
}

Hydrostatic

Answer 4

package com.keshav.hideactionbarandfooterexample;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.DecelerateInterpolator;
import android.widget.FrameLayout;
import android.widget.ImageButton;

import java.util.ArrayList;
import java.util.List;

import adapters.RecyclerAdapter;
import listners.HidingScrollListener;

public class MainActivity extends AppCompatActivity {

    private Toolbar mToolbar;
    private Toolbar toolbar_bottom;
    private ImageButton mFabButton;

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

        Log.e("keshav", "MainActivity called");

        initToolbar();
        mFabButton = (ImageButton) findViewById(R.id.fabButton);
        initRecyclerView();
    }

    private void initToolbar() {
        mToolbar = (Toolbar) findViewById(R.id.toolbar);
        toolbar_bottom = (Toolbar) findViewById(R.id.toolbar_bottom);
        setSupportActionBar(mToolbar);
        setSupportActionBar(toolbar_bottom);
        setTitle(getString(R.string.app_name));
        mToolbar.setTitleTextColor(getResources().getColor(android.R.color.white));
        toolbar_bottom.setTitleTextColor(getResources().getColor(android.R.color.white));


        toolbar_bottom.setVisibility(View.GONE);
    }

    private void initRecyclerView() {
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        RecyclerAdapter recyclerAdapter = new RecyclerAdapter(createItemList());
        recyclerView.setAdapter(recyclerAdapter);

        recyclerView.addOnScrollListener(new HidingScrollListener() {
            @Override
            public void onHide() {
                hideViews();
            }

            @Override
            public void onShow() {
                showViews();
            }
        });
    }

    private void hideViews() {
        // TODO (-mToolbar)  plus means  2 view above ho jaye or not visible to user
        mToolbar.animate().translationY(-mToolbar.getHeight()).setInterpolator(new AccelerateInterpolator(2));

        // TODO uncomment this Hide Footer in android when Scrolling
        // TODO (+mToolbar)  plus means  2 view forward ho jaye or not visible to user
        toolbar_bottom.animate().translationY(+toolbar_bottom.getHeight()).setInterpolator(new AccelerateInterpolator(2));

        // TODO keshav Hide Also Floatng Button In Android
        FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) mFabButton.getLayoutParams();
        int fabBottomMargin = lp.bottomMargin;
        mFabButton.animate().translationY(mFabButton.getHeight() + fabBottomMargin).setInterpolator(new AccelerateInterpolator(2)).start();
        // TODO keshav Hide Also Floatng Button In Android
    }

    private void showViews() {
        mToolbar.animate().translationY(0).setInterpolator(new DecelerateInterpolator(2));

        // TODO uncomment this Hide Footer in android when Scrolling
        toolbar_bottom.animate().translationY(0).setInterpolator(new DecelerateInterpolator(2));
        mFabButton.animate().translationY(0).setInterpolator(new DecelerateInterpolator(2)).start();
    }

    private List<String> createItemList() {
        List<String> itemList = new ArrayList<>();
        for (int i = 0; i < 20; i++) {
            itemList.add("Item " + i);
        }
        return itemList;
    }
}

=============================================
             RecyclerAdapter
=============================================
package adapters;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.keshav.hideactionbarandfooterexample.R;

import java.util.List;

/*
* RecyclerView Adapter that allows to add a header view.
* */
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private static final int TYPE_HEADER = 2;
    private static final int TYPE_ITEM = 1;
    private List<String> mItemList;

    public RecyclerAdapter(List<String> itemList) {
        mItemList = itemList;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        Context context = parent.getContext();
        if (viewType == TYPE_ITEM) {
            final View view = LayoutInflater.from(context).inflate(R.layout.recycler_item, parent, false);
            return RecyclerItemViewHolder.newInstance(view);
        } else if (viewType == TYPE_HEADER) {
            final View view = LayoutInflater.from(context).inflate(R.layout.recycler_header, parent, false);
            return new RecyclerHeaderViewHolder(view);
        }
        throw new RuntimeException("There is no type that matches the type " + viewType + " + make sure your using types correctly");
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
        if (!isPositionHeader(position)) {
            RecyclerItemViewHolder holder = (RecyclerItemViewHolder) viewHolder;
            String itemText = mItemList.get(position - 1); // header
            holder.setItemText(itemText);
        }
    }

    public int getBasicItemCount() {
        return mItemList == null ? 0 : mItemList.size();
    }


    @Override
    public int getItemViewType(int position) {
        if (isPositionHeader(position)) {
            return TYPE_HEADER;
        }

        return TYPE_ITEM;
    }

    @Override
    public int getItemCount() {
        return getBasicItemCount() + 1; // header
    }

    private boolean isPositionHeader(int position) {
        return position == 0;
    }

}

=====================================================
         RecyclerHeaderViewHolder
=====================================================
package adapters;

import android.support.v7.widget.RecyclerView;
import android.view.View;

public class RecyclerHeaderViewHolder extends RecyclerView.ViewHolder {
    public RecyclerHeaderViewHolder(View itemView) {
        super(itemView);
    }
}

=====================================================
              RecyclerItemViewHolder
=====================================================

package adapters;

import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.TextView;

import com.keshav.hideactionbarandfooterexample.R;


public class RecyclerItemViewHolder extends RecyclerView.ViewHolder {

    private final TextView mItemTextView;

    public RecyclerItemViewHolder(final View parent, TextView itemTextView) {
        super(parent);
        mItemTextView = itemTextView;
    }

    public static RecyclerItemViewHolder newInstance(View parent) {
        TextView itemTextView = (TextView) parent.findViewById(R.id.itemTextView);
        return new RecyclerItemViewHolder(parent, itemTextView);
    }

    public void setItemText(CharSequence text) {
        mItemTextView.setText(text);
    }

}

===================================================
            activity_main.xml
===================================================

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="match_parent"
                android:layout_height="match_parent">

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

    <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"/>

    <ImageButton
            android:id="@+id/fabButton"
            android:layout_width="56dp"
            android:layout_height="56dp"
            android:layout_gravity="bottom|right"
            android:layout_marginBottom="16dp"
            android:layout_marginRight="16dp"
            android:background="@drawable/fab_bcg"
            android:src="@drawable/ic_favorite_outline_white_24dp"
            android:contentDescription="@string/fab_description"/>


    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar_bottom"
        android:layout_width="match_parent"
        android:layout_alignParentBottom="true"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"/>

    </RelativeLayout>

</FrameLayout>


==================================================
    recycle_header.xml in layout folder
==================================================

<?xml version="1.0" encoding="utf-8"?>
<View xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="?attr/actionBarSize"/>

==================================================
    recycle_item.xml in layout folder
==================================================
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:layout_margin="8dp"
    card_view:cardCornerRadius="4dp">
    <TextView
        android:id="@+id/itemTextView"
        android:layout_width="match_parent"
        android:layout_height="?attr/listPreferredItemHeight"
        android:gravity="center_vertical"
        android:padding="8dp"
        style="@style/Base.TextAppearance.AppCompat.Body2"/>
</android.support.v7.widget.CardView>


=================================================
                      styles.xml
=================================================
<resources>

    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
    </style>

    <style name="AppThemeRed" parent="AppTheme">
        <item name="colorPrimary">@color/color_primary_red</item>
        <item name="colorPrimaryDark">@color/color_primary_red_dark</item>
    </style>

    <style name="AppThemeGreen" parent="AppTheme">
        <item name="colorPrimary">@color/color_primary_green</item>
        <item name="colorPrimaryDark">@color/color_primary_green_dark</item>
    </style>

    <style name="AppThemeBlue" parent="AppTheme">
        <item name="colorPrimary">@color/color_primary_blue</item>
        <item name="colorPrimaryDark">@color/color_primary_blue_dark</item>
        <item name="colorAccent">@color/color_accent_pink</item>
    </style>

</resources>

build.gradle Dependency

  compile 'com.android.support:appcompat-v7:25.3.1'
    compile 'com.android.support:recyclerview-v7:25.3.1'
    compile 'com.android.support:cardview-v7:25.3.1'
    compile 'com.android.support:design:25.3.1'

Directorate

drive.google.com/open?id=0BzBKpZ4nzNzUVi0xeU1UMjZHeFE ---- Whole – Directorate

Answer 5

@k0sh gave a fine solution. I want to update it to get a smooth animation while showing and hiding the layout. Replace complete code inside onNestedPreScroll() with the below code:

if (dy > 0) {

        CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) child.getLayoutParams();
        int viewBottomMargin = layoutParams.bottomMargin;
        child.animate().translationY(child.getHeight() + viewBottomMargin).setInterpolator(new LinearInterpolator()).start();

} else if (dy < 0) {

        child.animate().translationY(0).setInterpolator(new LinearInterpolator()).start();

}

Baiss

Answer 6

@k0sh's QuickReturnFloaterBehavior works but it sometimes not listen to the slight scrolls.

I am having contents in NestedScrollView with a LinearLayout as a bottom bar & didn't have the recycler view. so, I can't use other suggested answers.

Those who are having the same situation can use the BottomNavigationBehavior from this post Bottom Navigation Behavior. it works perfectly & useful.

When the current top-level view has a scrolling content, the bottom navigation should hide when it is scrolled down and retract back when the content is scrolled up. For this purpose, we need to be aware of the direction of the scroll. VerticalScrollingBehavior is a generic layout behavior that it is somehow an extension to the CoordinatorLayout.Behavior that dispatches events on for direction of scrolling.

source code for BottomNavigationBehavior - https://gist.github.com/NikolaDespotoski/1d6fef4949eb9be05a46#file-bottomnavigationbehavior-java

snippet from BottomNavigationBehavior

@Override
public void onDirectionNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed, @ScrollDirection int scrollDirection) {
    handleDirection(child, scrollDirection);
}

@Override
protected boolean onNestedDirectionFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY, @ScrollDirection int scrollDirection) {
    handleDirection(child, scrollDirection);
    return true;
}

private void handleDirection(V child, @ScrollDirection int scrollDirection) {
    if (!scrollingEnabled) return;
    if (scrollDirection == ScrollDirection.SCROLL_DIRECTION_DOWN && hidden) {
        hidden = false;
        animateOffset(child, 0);
    } else if (scrollDirection == ScrollDirection.SCROLL_DIRECTION_UP && !hidden) {
        hidden = true;
        animateOffset(child, child.getHeight());
    }
}

Sigrid