SetState() called in constructor

I've build a Custemized List. Now I include a Checkbox and if I would checked or unchecked , the following error was thrown: 'setState() called in constructor'

class Lists extends StatefulWidget{  
     @override
    _List createState() => _List();
}

class _List extends State<Lists> {  
  bool checkedvalue = true;
  @override
Widget build(BuildContext context) {

 return futureBuilder();
}

Widget futureBuilder(){  
  var futureBuilder = new FutureBuilder(
      future: rest.fetchPost(),
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        switch (snapshot.connectionState) {
          case ConnectionState.none:
          case ConnectionState.waiting:
            return new Text('loading...');
          default:
            if (snapshot.hasError)
              return new Text('Error: ${snapshot.error}');
            else                    
                return listBuilder(context, snapshot);            
        }
      }
 );

 return new Scaffold(         
      body: futureBuilder,
    );
}

Widget listBuilder(BuildContext context, AsyncSnapshot snapshot) {  
  List<rest.Status> values = snapshot.data;

  if (values == null || values.length == 0){
    return null;
  }


  int items = values.length;

  return ListView.builder(   
  itemCount: items,
  itemBuilder: (BuildContext context, int index) {
    String statusText;
    Image image ;
    Uint8List bytes;

    if(statusList.globalStatus != null){
      for(int i=0;i< statusList.globalStatus.length; i++){
        if(values[index].statusID == statusList.globalStatus[i].id){

            if(statusList.globalStatus[i].kurzform != null){
              statusText = statusList.globalStatus[i].kurzform;
            }else{
              statusText = statusList.globalStatus[i].kurzform;
            }

            if (statusList.globalStatus[i].icon != null){
              bytes = base64Decode(statusList.globalStatus[i].icon);
              image = new Image.memory(bytes) ;
            } 
        }

        if(image== null || statusText == null){            
          statusText= 'Kein Status';
          image=  new Image.asset('assets/null.png');
        }              
      }
    }   
    return new Container( 
      decoration: new BoxDecoration(
          border: Border(top: BorderSide(
          color: Colors.black26,
          width: 1
          )
        )
      ), 


      child:Column(
        children: <Widget>[
          CustomListItemTwo( 
            statusText: statusText,                               
            status:image,
            materialNR: values[index].uArtText,          
            material: values[index].untersuchungsMaterialName,
            probenArt:  values[index].probenart,
            eingansdatum: values[index].eingangsdatumText,
            patient: values[index].vorname + ' ' + values[index].nachname ,
            geburtsdatum: values[index].geburtstagText ,

          ),
          Checkbox(            
              value: checkedvalue ,           
              onChanged: (bool newValue) =>                
                setState(() {
                  checkedvalue = newValue; 
                })              
            ),
        ] 
      ),
    );
  }       
  );
}

}

I/flutter ( 5067): ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════ I/flutter ( 5067): The following assertion was thrown while handling a gesture: I/flutter ( 5067): setState() called in constructor: _List#9044e(lifecycle state: created, no widget, not mounted) I/flutter ( 5067): This happens when you call setState() on a State object for a widget that hasn't been inserted into I/flutter ( 5067): the widget tree yet. It is not necessary to call setState() in the constructor, since the state is I/flutter ( 5067): already assumed to be dirty when it is initially created.