How to set minimum height of SliverAppBar within NestedScrollView in Flutter

I don't know since exactly when, but as of now, you can also use the collapsedHeight property, documented as below:

https://api.flutter.dev/flutter/material/SliverAppBar/collapsedHeight.html

Currently I am on flutter 1.20.1 and I have this property available.

This is Actually an requested Feature - https://github.com/flutter/flutter/issues/21298

A work Around is to use Bottom

SliverAppBar(
              // this is where I would like to set some minimum constraint
              expandedHeight: 300,
              floating: false,
              pinned: true,
              bottom: PreferredSize(                       // Add this code
                preferredSize: Size.fromHeight(60.0),      // Add this code
                child: Text(''),                           // Add this code
              ),                                           // Add this code
              flexibleSpace: Container(
                padding: EdgeInsets.all(10),
                height: 340,
                width: double.infinity,
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.end,
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Container(
                      height: 40,
                    ),
                    Container(
                      height: 60,
                    ),
                    Expanded(child: Container()),
                    Text('TEST'),
                  ],
                ),
                decoration: BoxDecoration(
                    image: DecorationImage(
                        image: NetworkImage('https://picsum.photos/400/400'),
                        fit: BoxFit.cover)),
              ),
            )

Simply use collapsedHeight and specify your minimum height.

 SliverAppBar(
  // Display a placeholder widget to visualize the shrinking size.
  flexibleSpace: Placeholder(),
  expandedHeight: 300,
  collapsedHeight: 60,
);