Updated bottom navigation behavior for BottomNavigationView

BottomNavigationBehavior.java

import android.content.Context;
import android.content.res.TypedArray;
import android.os.Build;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.design.widget.CoordinatorLayout;
import android.support.design.widget.Snackbar;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPropertyAnimatorCompat;
import android.support.v4.view.animation.LinearOutSlowInInterpolator;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.Interpolator;

/**
 * Created by Nikola D. on 3/15/2016.
 */
public final class BottomNavigationBehavior<V extends View> extends VerticalScrollingBehavior<V> {
    private static final Interpolator INTERPOLATOR = new LinearOutSlowInInterpolator();
    private final BottomNavigationWithSnackbar mWithSnackBarImpl = Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP ? new LollipopBottomNavWithSnackBarImpl() : new PreLollipopBottomNavWithSnackBarImpl();
    private int mTabLayoutId;
    private boolean hidden = false;
    private ViewPropertyAnimatorCompat mOffsetValueAnimator;
    private ViewGroup mTabLayout;
    private int mSnackbarHeight = -1;
    private boolean scrollingEnabled = true;
    private boolean hideAlongSnackbar = false;
    int[] attrsArray = new int[]{
            android.R.attr.id, android.R.attr.elevation};
    private int mElevation = 8;

    public BottomNavigationBehavior() {
        super();
    }

    public BottomNavigationBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = context.obtainStyledAttributes(attrs,
                attrsArray);
        mTabLayoutId = a.getResourceId(0, View.NO_ID);
        mElevation = a.getResourceId(1, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, mElevation, context.getResources().getDisplayMetrics()));
        a.recycle();
    }

    public static <V extends View> BottomNavigationBehavior<V> from(@NonNull V view) {
        ViewGroup.LayoutParams params = view.getLayoutParams();
        if (!(params instanceof CoordinatorLayout.LayoutParams)) {
            throw new IllegalArgumentException("The view is not a child of CoordinatorLayout");
        }
        CoordinatorLayout.Behavior behavior = ((CoordinatorLayout.LayoutParams) params)
                .getBehavior();
        if (!(behavior instanceof BottomNavigationBehavior)) {
            throw new IllegalArgumentException(
                    "The view is not associated with BottomNavigationBehavior");
        }
        return (BottomNavigationBehavior<V>) behavior;
    }

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, V child, View dependency) {
        mWithSnackBarImpl.updateSnackbar(parent, dependency, child);
        return dependency instanceof Snackbar.SnackbarLayout;
    }

    @Override
    public void onDependentViewRemoved(CoordinatorLayout parent, V child, View dependency) {
        updateScrollingForSnackbar(dependency, child, true);
        super.onDependentViewRemoved(parent, child, dependency);
    }

    private void updateScrollingForSnackbar(View dependency, V child, boolean enabled) {
        if (dependency instanceof Snackbar.SnackbarLayout) {
            scrollingEnabled = enabled;
            if (!hideAlongSnackbar && ViewCompat.getTranslationY(child) != 0) {
                ViewCompat.setTranslationY(child, 0);
                hidden = false;
                hideAlongSnackbar = true;
            } else if (hideAlongSnackbar) {
                hidden = true;
                animateOffset(child, -child.getHeight());
            }
        }
    }

    @Override
    public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) {
        updateScrollingForSnackbar(dependency, child, false);
        return super.onDependentViewChanged(parent, child, dependency);
    }

    @Override
    public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {
        boolean layoutChild = super.onLayoutChild(parent, child, layoutDirection);
        if (mTabLayout == null && mTabLayoutId != View.NO_ID) {
            mTabLayout = findTabLayout(child);
            elevateNavigationView();
        }

        return layoutChild;
    }

    @Nullable
    private ViewGroup findTabLayout(@NonNull View child) {
        if (mTabLayoutId == 0) return null;
        return (ViewGroup) child.findViewById(mTabLayoutId);
    }

    @Override
    public void onNestedVerticalOverScroll(CoordinatorLayout coordinatorLayout, V child, @ScrollDirection int direction, int currentOverScroll, int totalOverScroll) {
    }

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

    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());
        }
    }

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

    private void animateOffset(final V child, final int offset) {
        ensureOrCancelAnimator(child);
        mOffsetValueAnimator.translationY(offset).start();
    }



    private void ensureOrCancelAnimator(@NonNull  V child) {
        if (mOffsetValueAnimator == null) {
            mOffsetValueAnimator = ViewCompat.animate(child);
            mOffsetValueAnimator.setDuration(100);
            mOffsetValueAnimator.setInterpolator(INTERPOLATOR);
        } else {
            mOffsetValueAnimator.cancel();
        }
    }

    private void elevateNavigationView() {
        if (mTabLayout != null) {
            ViewCompat.setElevation(mTabLayout, mElevation);
        }
    }

    public boolean isScrollingEnabled() {
        return scrollingEnabled;
    }

    public void setScrollingEnabled(boolean scrollingEnabled) {
        this.scrollingEnabled = scrollingEnabled;
    }

    public void setHidden(V view, boolean bottomLayoutHidden) {
        if (!bottomLayoutHidden && hidden) {
            animateOffset(view, 0);
        } else if (bottomLayoutHidden && !hidden) {
            animateOffset(view, -view.getHeight());
        }
        hidden = bottomLayoutHidden;
    }

    private interface BottomNavigationWithSnackbar {
        void updateSnackbar(CoordinatorLayout parent, View dependency, View child);
    }

    private class PreLollipopBottomNavWithSnackBarImpl implements BottomNavigationWithSnackbar {

        @Override
        public void updateSnackbar(CoordinatorLayout parent, View dependency, View child) {
            if (dependency instanceof Snackbar.SnackbarLayout) {
                if (mSnackbarHeight == -1) {
                    mSnackbarHeight = dependency.getHeight();
                }

                int targetPadding = child.getMeasuredHeight();

                int shadow = (int) ViewCompat.getElevation(child);
                ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams) dependency.getLayoutParams();
                layoutParams.bottomMargin = targetPadding - shadow;
                child.bringToFront();
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
                    child.getParent().requestLayout();
                    ((View) child.getParent()).invalidate();
                }

            }
        }
    }

    private class LollipopBottomNavWithSnackBarImpl implements BottomNavigationWithSnackbar {

        @Override
        public void updateSnackbar(CoordinatorLayout parent, View dependency, View child) {
            if (dependency instanceof Snackbar.SnackbarLayout) {
                if (mSnackbarHeight == -1) {
                    mSnackbarHeight = dependency.getHeight();
                }
                int targetPadding = (mSnackbarHeight +
                        child.getMeasuredHeight());
                dependency.setPadding(dependency.getPaddingLeft(),
                        dependency.getPaddingTop(), dependency.getPaddingRight(), targetPadding
                );
            }
        }
    }
}

VerticalScrollingBehavior.java

import android.content.Context;
import android.os.Parcelable;
import android.support.annotation.IntDef;
import android.support.design.widget.CoordinatorLayout;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.WindowInsetsCompat;
import android.util.AttributeSet;
import android.view.View;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

/**
 * Created by Nikola on 11/22/2015.
 */
public abstract class VerticalScrollingBehavior<V extends View> extends CoordinatorLayout.Behavior<V> {

    private int mTotalDyUnconsumed = 0;
    private int mTotalDy = 0;
    @ScrollDirection
    private int mOverScrollDirection = ScrollDirection.SCROLL_NONE;
    @ScrollDirection
    private int mScrollDirection = ScrollDirection.SCROLL_NONE;

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

    public VerticalScrollingBehavior() {
        super();
    }

    @Retention(RetentionPolicy.SOURCE)
    @IntDef({ScrollDirection.SCROLL_DIRECTION_UP, ScrollDirection.SCROLL_DIRECTION_DOWN})
    public @interface ScrollDirection {
        int SCROLL_DIRECTION_UP = 1;
        int SCROLL_DIRECTION_DOWN = -1;
        int SCROLL_NONE = 0;
    }


    /*
       @return Overscroll direction: SCROLL_DIRECTION_UP, CROLL_DIRECTION_DOWN, SCROLL_NONE
   */
    @ScrollDirection
    public int getOverScrollDirection() {
        return mOverScrollDirection;
    }


    /**
     * @return Scroll direction: SCROLL_DIRECTION_UP, SCROLL_DIRECTION_DOWN, SCROLL_NONE
     */

    @ScrollDirection
    public int getScrollDirection() {
        return mScrollDirection;
    }


    /**
     * @param coordinatorLayout CoordinatoyLayout parent
     * @param child             View child
     * @param direction         Direction of the overscroll: SCROLL_DIRECTION_UP, SCROLL_DIRECTION_DOWN
     * @param currentOverScroll Unconsumed value, negative or positive based on the direction;
     * @param totalOverScroll   Cumulative value for current direction
     */
    public abstract void onNestedVerticalOverScroll(CoordinatorLayout coordinatorLayout, V child, @ScrollDirection int direction, int currentOverScroll, int totalOverScroll);

    /**
     * @param scrollDirection Direction of the overscroll: SCROLL_DIRECTION_UP, SCROLL_DIRECTION_DOWN
     */
    public abstract void onDirectionNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed, @ScrollDirection int scrollDirection);

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

    @Override
    public void onNestedScrollAccepted(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) {
        super.onNestedScrollAccepted(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target) {
        super.onStopNestedScroll(coordinatorLayout, child, target);
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
        if (dyUnconsumed > 0 && mTotalDyUnconsumed < 0) {
            mTotalDyUnconsumed = 0;
            mOverScrollDirection = ScrollDirection.SCROLL_DIRECTION_UP;
        } else if (dyUnconsumed < 0 && mTotalDyUnconsumed > 0) {
            mTotalDyUnconsumed = 0;
            mOverScrollDirection = ScrollDirection.SCROLL_DIRECTION_DOWN;
        }
        mTotalDyUnconsumed += dyUnconsumed;
        onNestedVerticalOverScroll(coordinatorLayout, child, mOverScrollDirection, dyConsumed, mTotalDyUnconsumed);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        if (dy > 0 && mTotalDy < 0) {
            mTotalDy = 0;
            mScrollDirection = ScrollDirection.SCROLL_DIRECTION_UP;
        } else if (dy < 0 && mTotalDy > 0) {
            mTotalDy = 0;
            mScrollDirection = ScrollDirection.SCROLL_DIRECTION_DOWN;
        }
        mTotalDy += dy;
        onDirectionNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, mScrollDirection);
    }


    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY, boolean consumed) {
        super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
        mScrollDirection = velocityY > 0 ? ScrollDirection.SCROLL_DIRECTION_UP : ScrollDirection.SCROLL_DIRECTION_DOWN;
        return onNestedDirectionFling(coordinatorLayout, child, target, velocityX, velocityY, mScrollDirection);
    }

    protected abstract boolean onNestedDirectionFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY, @ScrollDirection int scrollDirection);

    @Override
    public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY) {
        return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
    }

    @Override
    public WindowInsetsCompat onApplyWindowInsets(CoordinatorLayout coordinatorLayout, V child, WindowInsetsCompat insets) {

        return super.onApplyWindowInsets(coordinatorLayout, child, insets);
    }

    @Override
    public Parcelable onSaveInstanceState(CoordinatorLayout parent, V child) {
        return super.onSaveInstanceState(parent, child);
    }

}

@laszlo-galosi Sorry for delayed response. Yes, Behavior MUST find the bottomnavigationview so it can set 8dp or do it in your xml.

Cheers,

Hi Nikola, thanks for the great work, I wonder how can we expand the bottom bar manually with some method similar to appbar.setExpanded(boolean)?

[Updated]

I just wrote the method below based on your code:

private void expandBottomBar(View bottomBar){
    if (ViewUnit.getWindowHeight(context) < (int) bottomBar.getY() + bottomBar.getHeight()){
        ViewCompat.animate(bottomBar).setDuration(100)
            .setInterpolator(BottomNavigationBehavior.INTERPOLATOR)
            .translationY(0).start();
    }
}

@ghost There is a method setHidden(V view, boolean bottomLayoutHidden) it can be accessed:

BottomNavigationBehavior behavior = BottomNavigationBehavior.from(mBottomNavigationView);
if(behavior != null){
   behavior.setHidden(mBottomNavigationView, true); //or false
}

I believe animateOffset should be called with +view.getHeight() when bottomLayoutHidden == true
as per te following fix

public void setHidden(V view, boolean bottomLayoutHidden) {
        if (!bottomLayoutHidden && hidden) {
            animateOffset(view, 0);
        } else if (bottomLayoutHidden && !hidden) {
            animateOffset(view, view.getHeight());
        }
        hidden = bottomLayoutHidden;
    }