How to use setState() function inside SearchDelegate?

I am using a list with Check Box in it. The check box are used to select the items in the list. I have implemented a Search function using SearchDelegate.

Reference with below link

How to Set/Update Sate of StatefulWidget from other StatefulWidget in Flutter?

I have called the setState of parent from SearchDelegate.

But when I select an Item from search delegate the checkbox is not animating, when I hit the back button in the search bar, the value has been changed in the List.

Checkbox(
      value: list[index].isSelected,
      onChanged: (val) {
        this.parent.setState((){
        this.parent.widget.invoiceList[index].isSelected = val;
  });
});

I just want the check box to be animated while tapping it from the search delegate. Thank you.