top_sheet_scroll.java

int currentTop = child.getTop();
int newTop = currentTop - dy;
if (dy > 0) {
    if (!ViewCompat.canScrollVertically(target, 1)) {
        if (newTop >= mMinOffset || mHideable) {
            consumed[1] = dy;
            ViewCompat.offsetTopAndBottom(child, -dy);
            setStateInternal(STATE_DRAGGING);
        } else {
            consumed[1] = currentTop - mMinOffset;
            ViewCompat.offsetTopAndBottom(child, -consumed[1]);
            setStateInternal(STATE_COLLAPSED);
        }
    }
} else if (dy < 0) {
    if (newTop < mMaxOffset) {
        consumed[1] = dy;
        ViewCompat.offsetTopAndBottom(child, -dy);
        setStateInternal(STATE_DRAGGING);
    } else {
        consumed[1] = currentTop - mMaxOffset;
        ViewCompat.offsetTopAndBottom(child, -consumed[1]);
        setStateInternal(STATE_EXPANDED);
    }
}