Question

我正在尝试使用可使用复选框选择的项目列表视图来实现屏幕。这是主屏幕和复选框的代码：

class InterestHobbies extends StatefulWidget {
  @override
  _InterestHobbiesState createState() => _InterestHobbiesState();
}

class _InterestHobbiesState extends State<InterestHobbies> {

  final interests = [
    ModelCheckbox(title: 'Sports'),
    ModelCheckbox(title: 'Sports'),
    ModelCheckbox(title: 'Sports'),
    ModelCheckbox(title: 'Sports'),
    ModelCheckbox(title: 'Sports'),
    ModelCheckbox(title: 'Sports'),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: ListView(
        children: [
          ...interests.map((interest) => null).toList(),
        ],
      ),
    );
  }

  Widget buildSingleCheckbox(ModelCheckbox interest) => buildCheckbox(
    interest: interest,
    onClicked: (){
      setState(() {
        final newValue = !interest.value;
        interest.value = newValue;
      });
    }
  );

  Widget buildCheckbox({
    @required ModelCheckbox interest,
    @required VoidCallback onClicked,
  }) =>
      ListTile(
        onTap: onClicked,

        leading: Checkbox(
          value: interest.value,
          onChanged: (value) => onClicked(),
        ),
        title: Text(interest.title),
      );
}

我还创建了一个模型文件：

class ModelCheckbox {
  String title;
  bool value;

  ModelCheckbox({
    @required this.title,
    this.value = false,
  });
}

我收到以下错误：

The getter 'key' was called on null.
Receiver: null
Tried calling: key

Null check operator used on a null value

有人知道为什么吗？我将值作为兴趣传递，并相应地创建了模型，以便能够动态显示标题而不是硬编码。

Answer 1

您正在将兴趣列表的每个元素映射到 null。 ListView 只能将 Widgets 作为其子项。

试试

  body: ListView(
    children: interests.map((interest) => buildSingleCheckbox(interest)).toList(),
  ),

在 null flutter 错误时调用了 getter 'Key'

1 个答案: