How to automatically select all items above the selected one & deselect all items below the deselected one flutter

Question

  for (var item in _data)
    ListView.builder(
      shrinkWrap: true,
      itemCount: _data.length,
      itemBuilder: (context, index){
    return CheckboxListTile(
      value: item.isChecked,
      onChanged: (value) {
        setState(() {
          for (var i = 0; i <= _data.indexOf(item); i++) {
            _data[i].isChecked = value!;
          }
        }
        );
      },
    );

Answer 1

From what I understood from your question,

Try this,

setState(() {
 for (var i = 0; i < _data.length; i++) {
   if(i <= index){
    _data[i].isChecked = true;
   } else {
    _data[i].isChecked = false;
   }
 }