NoSuchMethodError : The getter 'title' was called on null. Receiver : null. Tried calling: title. //Anyone please

Question

这些是我的一些 todo_detail.dart 代码。请帮我。在调试控制台中显示

The relevant error-causing widget was
TodoDetail
lib/Screens/todo_list.dart:100
When the exception was thrown, this was the stack
#1      TodoDetailState.build
package:todo_list/Screens/todo_detail.dart:35



class TodoDetail extends StatefulWidget {
  TodoDetail(this.todo, this.appBarTitle);

  final String appBarTitle;
  final Todo todo;

  @override
  State<StatefulWidget> createState() {
    return TodoDetailState(this.todo, this.appBarTitle);
  }
}

class TodoDetailState extends State<TodoDetail> {
  DatabaseHelper helper = DatabaseHelper();

  String appBarTitle;
  Todo todo;

  TextEditingController titleController = TextEditingController();
  TextEditingController descriptionController = TextEditingController();

  TodoDetailState(this.todo, this.appBarTitle);

  @override
  Widget build(BuildContext context) {
    TextStyle textStyle = Theme.of(context).textTheme.headline6;
    final Todo todo = ModalRoute.of(context).settings.arguments;

    titleController.text = todo.title;
    descriptionController.text = todo.description,......

This is the screenshot 在我的物理设备上构建后的错误

Answer 1

Todo 在上面的代码中作为 Widget 参数传递，因此，我们可以通过以下方式访问它：

final Todo todo = widget.todo;

完整代码示例：

class TodoDetailState extends State<TodoDetail> {
  DatabaseHelper helper = DatabaseHelper();

  String appBarTitle;
  Todo todo;

  TextEditingController titleController = TextEditingController();
  TextEditingController descriptionController = TextEditingController();

  TodoDetailState(this.todo, this.appBarTitle);

  @override
  Widget build(BuildContext context) {
       TextStyle textStyle = Theme.of(context).textTheme.headline6;
       final Todo todo = widget.todo;
       titleController.text = todo.title;
       descriptionController.text = todo.description;
       return Container();
    }
}