StickyUpDownDemo. 一个界面上有一个`headerView`、一个`toolbar`和一个`tableview`，在`tableview`向上滚动时，`headerView`和`toolbar`也向上移动，在`headerView`完全消失时，`toolbar`就固定在导航条下面，`tableview`就固定在`toolbar`下面。

Problem

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.

Audience

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.

Market

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.

Pricing

The full read on this project is a sign-in away — what it solves, who it serves, and where it sits in the market.