Take a look at shared preference

When you are adding the text to a list from the on saved method add the text to a List. Save this list in shared preferences. When you create the task card take it from shared preferences

i want to make a to do list with input textField but when i refresh the page the list of tasks refreshs too so it become as default
to explain it i want to send a task by the text field and the task enter the list and after we will add a task to the bottom of the listView

class Tasks extends StatefulWidget {
  List<tasks> L = [];
  bool b = false;

  Tasks(this.L, this.b);

  @override
  State<Tasks> createState() => _TasksState();
}

class _TasksState extends State<Tasks> {
  final ctrl = TextEditingController();
  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
    ctrl.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Column(children: [
      Visibility(maintainInteractivity: true,maintainState: true,maintainSize: true,maintainAnimation: true,
          visible: this.widget.b,
          child: TextField(
            controller: ctrl,focusNode: FocusNode(descendantsAreFocusable: true),
            onSubmitted: (text) => {
              setState(() {
                String s = text;
                this.widget.L.add(tasks(text, []));
                ctrl.clear();
              })
            },
            decoration:
                InputDecoration(fillColor: Colors.white, hintText: "dafaf"),
            style: TextStyle(color: Colors.white, fontWeight: FontWeight.w400),
          )),
      Expanded(
          child: ListView.builder(
        itemCount: this.widget.L.length,
        itemBuilder: (BuildContext context, int index) {
          return Card(
            color: Colors.black,
            child: Column(
              children: [
                ListTile(
                    textColor: Colors.white,
                    iconColor: Colors.white,
                    title: Row(children: [
                      Checkbox(
                          value: false,
                          checkColor: Color.fromRGBO(85, 85, 85, 1),
                          tristate: false,
                          onChanged: (value) {}),
                      Text(this.widget.L[index].tite)
                    ])),
              ],
            ),
          );
        },
      ))
    ]);
  }
}