未处理的异常：类型 'Null' 不是类型 'Future<Never>' 的子类型

Question

我已经尝试将 Future 和字符串都设为 nullable，但出了点问题请帮忙？

floatingActionButton: FloatingActionButton(
    onPressed: () {
      getName().then((value) {
        print(value);
        throw("error!!!!!");
      }).catchError((error) => print(error.toString()));
    },
    child: Icon(Icons.add),
),

在我的 class

某处的构建方法之外

Future<String> getName() async =>'Some String';

Answer 1

你可以试试这个

getName().then((value) {
                print(value);
                throw ("error!!!!");
              }).catchError((error) {
                print("catch error :: " + error.toString());
              });

该代码打印 catch error :: error!!!!。是你想要的吗？

Answer 2

所以这修复了我的代码

floatingActionButton: FloatingActionButton(
        onPressed: () => getName().then((value){
          //  the return type of an error handler is not acceptable
          // as the value of future.
          // after lambda expression is executed it gone so
          // we wouldn't know where the error came from
          // because also the return type is dynamic so we 
          //can't get to a datatype interface so it may be null since it's dynamic 
          if(value is FutureOr) {
            throw("error");
          }
        }).catchError((error) =>  print(error.toString()) ) ,

未处理的异常：类型 'Null' 不是类型 'Future<Never>' 的子类型

Unhandled Exception: type 'Null' is not a subtype of type 'Future<Never>'

dart

flutter

dart-null-safety