QuickReturnFooterBehavior

public class QuickReturnFooterBehavior extends CoordinatorLayout.Behavior<View> {

    private static final Interpolator INTERPOLATOR = new FastOutSlowInInterpolator();
    private static final long ANIMATION_DURATION = 200;

    private int dyDirectionSum;
    private boolean isShowing;
    private boolean isHiding;

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

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

    @Override
    public void onNestedPreScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull View child, @NonNull View target, int dx, int dy, @NonNull int[] consumed, int type) {
        // 스크롤이 반대방향으로 전환
        if (dy > 0 && dyDirectionSum < 0
                || dy < 0 && dyDirectionSum > 0) {
            child.animate().cancel();
            dyDirectionSum = 0;
        }

        dyDirectionSum += dy;

        if (dyDirectionSum > child.getHeight()) {
            hideView(child);
        } else if (dyDirectionSum < -child.getHeight()) {
            showView(child);
        }
    }

    private void hideView(final View view) {
        if (isHiding || view.getVisibility() != View.VISIBLE) {
            return;
        }

        ViewPropertyAnimator animator = view.animate()
                .translationY(view.getHeight())
                .setInterpolator(INTERPOLATOR)
                .setDuration(ANIMATION_DURATION);

        animator.setListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animator) {
                isHiding = true;
            }

            @Override
            public void onAnimationEnd(Animator animator) {
                isHiding = false;
                view.setVisibility(View.INVISIBLE);
            }

            @Override
            public void onAnimationCancel(Animator animator) {
                // 취소되면 다시 보여줌
                isHiding = false;
                showView(view);
            }

            @Override
            public void onAnimationRepeat(Animator animator) {
                // no-op
            }
        });

        animator.start();
    }

    private void showView(final View view) {
        if (isShowing || view.getVisibility() == View.VISIBLE) {
            return;
        }
        ViewPropertyAnimator animator = view.animate()
                .translationY(0)
                .setInterpolator(INTERPOLATOR)
                .setDuration(ANIMATION_DURATION);

        animator.setListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animator) {
                isShowing = true;
                view.setVisibility(View.VISIBLE);
            }

            @Override
            public void onAnimationEnd(Animator animator) {
                isShowing = false;
            }

            @Override
            public void onAnimationCancel(Animator animator) {
                // 취소되면 다시 숨김
                isShowing = false;
                hideView(view);
            }

            @Override
            public void onAnimationRepeat(Animator animator) {
                // no-op
            }
        });

        animator.start();
    }
}