I'm trying to make a collapsible SliverAppBar that has an expanded state and a collapsed state and no intermediate states. That means that you cannot scroll down a little bit and leave the app bar in a partial transition. When left in this position it should animate either to a collapsed or expanded state based on where it's going to land.
The scroll position should automatically adjust itself to match. In other words, if the app bar expands it should simultaneously push the content down with it.