Why when I open an ExpansionTile it scrolls to top? How to keep scrolled at the item selected-CodePudding

I have the following list of expansionTiles inside a listView (to be able to scroll because there are more than 20 items), and when I tap on it, it shows another content in a panel. I want to open only one item per time (if I open one the other opened has to close) and this part is working now. See the code:

Expanded(
  child: ListView.separated(
    itemCount: snapshot.data[i].products.length,
    key: Key('builder ${selected.toString()}'),
    itemBuilder: (ctx, index) {
      return ExpansionTile(
        title: Row(
          children: [
           Text('${snapshot.data[i].products[index].code} - ', style: TextStyle(fontWeight: FontWeight.bold),),
           Expanded(
             child: Text('${snapshot.data[i].products[index].price == null ? "0.00" : NumberFormat.simpleCurrency(locale: 'pt_Br').format(snapshot.data[i].products[index].price)}', style: TextStyle(fontWeight: FontWeight.bold, color: Colors.red),)
           )
         ],
        ),
        children: [
          Container(
            height: MediaQuery.of(context).size.height * 0.60,
            width: MediaQuery.of(context).size.width,
            child: ProductsColorWidget(snapshot.data[i].products[index], snapshot.data[i], refresh)
          ),
        ],
        onExpansionChanged: ((newState) {
          if(newState){
            setState(() {
              selected = index;
            });
          }else{
            setState(() {
              selected = -1;
            });
          }
        }),
        key: Key(index.toString()),
        initiallyExpanded: index == selected,
      );
    },
    separatorBuilder: (context, index) {
      return Divider();
    },
  )
)

The problem is every time I open an item it rebuilds the screen and I have to scroll again to find the item I clicked on.

For example, I tapped in the last item, so, I want to see that item's content, but the list scrolls to the first item, and I have to scroll back to the last one to see its content;

What I want: Not scroll to the list init every time I tap in one item. Just tap in an item, open and show its content.. or scroll to the item tapped.

CodePudding user response：

ListView.builder(
  itemCount: snapshot.data[i].products.length,
  itemBuilder: (BuildContext context, int index) {
    return ExpansionTile(
      key: Key('builder ${selected.toString()}'),
      initiallyExpanded: index == selected,