callback in react native?

Question

Android

There is a basic module CalendarModule which is made according to the documentation https://reactnative.dev/docs/native-modules-android , in order to return a string from the module I use the following code:

@ReactMethod
    public String returnString(Callback callback) {
        callback.invoke("string111");
    }

but when I build I get an error

CalendarModule.java:29: error: cannot find symbol Callback

i.e. java cannot find the callback interface, tell me what to do to make it work

Answer 1

Import may be missing some