SliverList setState to Affect Only Selected Item Flutter

I have a button on every item on my SliverList. When I click a specific list item button, I wish it change to a different widget by using setState. Only that specific item button should change to a different widget while the rest on the list retains its own item button.

Example below. The problem of course is that when I click any button on the list, all buttons on every item on the list changes. What is needed so that it affects only the specific item on the list whose button was pressed?

SliverList(
   delegate: SliverChildBuilderDelegate((BuildContext context, int index) {
     final item = gd[index];
     return Container(
       child: Column(
         children: [
           item.mypicwidget(context,item.pid),
           _shownewwidget
              ? item.newwidget(context)
              : RaisedButton(
                   onPressed: () {
                      setState(() {
                        _shownewwidget=true;
                      });
                   },
                  child: const Text('Press Me'),
                ),
]
),
);