How can I resolve "LateInitializationError: Field 'userMap' has not been initialized."

Question

late Map<String,dynamic> userMap;

bool isLoading = false;
final TextEditingController _search = TextEditingController();


void onSearch() async{
FirebaseFirestore _firestore = FirebaseFirestore.instance;
setState(() {
  isLoading = true;
});
await _firestore.collection('users').where('email', isEqualTo: _search.text)
    .get().then((value) {
      setState(() {
        userMap = value.docs[0].data();
        isLoading = false;
      });
      print(userMap);
});

}

代码的第一部分工作正常，但是当我想创建我的 ListTile 时弹出错误。

userMap != null ?
        ListTile(
          title: Text(userMap['name']),
          subtitle: Text(userMap['email']),
        ):Container(),

如果有人能帮助我，那将是非常感谢！

Answer 1

当你有一个不可为空的变量时可以使用late关键字，但你只想稍后初始化它。变量永远不会为空，只有两种状态，未初始化或使用非空值初始化。

如果您想使用可为空的变量，您只能将 ? 关键字添加到变量中，例如 Map<String,dynamic>? userMap;

How can I resolve "LateInitializationError: Field 'userMap' has not been initialized."

How can I resolve "LateInitializationError: Field 'userMap' has not been initialized."

java

widget

dart

flutter