Flutter saving data dynamically

Question

I want to save data from my TextField in my device. I accomplish this by TextEditingController. But now, I want to do that dynamically. I will have meany TextField's and I only learned how to do it statically. Can someone write demo application showing how I should do it, or explain somehow?

I was trying to find anything on the internet, sadly I didn't

(in the end, I want my application to use this data if I close application or restart phone)

This class is saving data statically, but I think the problem is with controller:

class Storage {
  //gets path of the file
  Future<String> get _localPath async {
    final dir = await getApplicationDocumentsDirectory();
    return dir.path;
  }

  //gets the location of the file
  Future<File> get _localFile async {
    final path = await _localPath;
    return File("$path/db.txt");
  }

  //write to the file
  Future<File> writeData(String message) async {
    final file = await _localFile;
    return file.writeAsString("$message");
  }

  //read from the file
  Future<String> readData() async {
    try {
      final file = await _localFile;
      String body = await file.readAsString();
      return body;
    } catch (e) {
      return e.toString();
    }
  }
}

Answer 1

等待大神答复