Smooth Coordinatorlayout Scrolling, FlingBehavior

activity_main.xml

<!-- Add behaviour to AppBarLayout -->
<CoordinatorLayout>
   <AppBarLayout
      app:layout_behavior="com.farukcankaya.FlingBehavior">
     ...
  </AppBarLayout>
  <CollapsingToolbarLayout>
    <Toolbar/>
    ...
  </CollapsingToolbarLayout>

  <RecyclerView />
  ...
</CoordinatorLayout>

FlingBehavior.java

public final class FlingBehavior extends AppBarLayout.Behavior {
    private static final int TOP_CHILD_FLING_THRESHOLD = 3;
    private boolean isPositive;

    public FlingBehavior() {
    }

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

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
            velocityY = velocityY * -1;
        }
        View v = target;
        if (target instanceof SwipeRefreshLayout && velocityY < 0) {
            v = ((SwipeRefreshLayout) target).getChildAt(0);
        }
        if (v instanceof RecyclerView && velocityY < 0) {
            final RecyclerView recyclerView = (RecyclerView) v;
            final View firstChild = recyclerView.getChildAt(0);
            final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
            consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;
        }
        return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        isPositive = dy > 0;
    }
}