SliverAppBar needs a custom widget area at the bottom of the layout #129868
Description
Is there an existing issue for this?
- I have searched the existing issues
- I have read the guide to filing a bug
Use case
I want to add some custom dropdown controls below the title text in the SliverAppBar. There is no clean way to do this currently.
I have a SliverAppBar that contains a FlexibleSpaceBar with a cover image, a drawer, and some title text.
I tried adding these controls to the FlexibleSpaceBar, by hijacking background with a Column widget, but clearly the layout was not designed for this, and it's pretty much impossible to get the layout and animation right.
I added a SliverPersistentHeader, which does place the controls below the SliverAppBar, but there are several issues:
- Really I just want the extra controls in the
SliverPersistentHeaderto appear as part of theSliverAppBar, not have their own hide/show semantics that are different from those of theSliverAppBar. - The pinning/floating behavior of
SliverPersistentHeaderis bizarre at best -- I want this header to appear whenever theSliverAppBaris maximized and I drag down, at any position in the wrappingCustomScrollView. However,SliverPersistentHeaderseems to pin at an absolute position near the top of theCustomScrollView, so it only appears if I scroll theCustomScrollViewnearly to the top. Seefloatingbehavior ofSliverPersistentHeaderdoes not match that ofSliverAppBar#129869. - There is a tiny half-pixel gap between the
SliverAppBarand theSliverPersistentHeader. This shows up as a faint white line occasionally, since both the app bar and the header have non-white backgrounds. See There is a half-pixel gap betweenSliverAppBarandSliverPersistentHeader#129870.
Proposal
Please add a SliverAppBar.footer field that allows the user to add a Widget to the bottom of the SliverAppBar.
It would also be great if this footer were dyamically-sizeable, so that content could be added to or removed from it, and it would take only as much vertical space as necessary to wrap the content.