在android / java中传递信息的最佳做法

Question

Hi I'm writing an app in android and was wondering about best practices and potential advantages and disadvantages of each the methods presented below if you want to call a method defined in Class A from Class B or pass information from class A to B

Method1: Passing Method A as argument.

class A {
    B object;
    A(B object) {
        this.object = object;
    }
    void someMethod() {
        object.someOtherMethod();
    }
}
class B {
    void someOtherMethod(){
        ...
    }
}

Method2: Defining a interface.

class A {
    Helper helper;
    A(Helper helper) {
        this.helper= helper;
    }
    void someMethod() {
        helper.someOtherMethod();
    }
    interface Helper {
        void someOtherMethod();
    }
}
class B implements A.Helper {
    @Override
    void someOtherMethod(){
        ...
    }
}

In the android docs I read that the preferred way for passing information from a Fragment to an Activity is the second method. But was wondering why this is the case?

Answer 1

If I'm understanding your question correctly, this sounds more like a question about why/when to use interfaces in OOP.

The best example would be when we add another class, C. If class C implements A.Helper as well, then you can pass C into A no problem, using the second method. If you use the first method, C can not be passed into A, because it is expecting an object of type B.

Some further reading: https://softwareengineering.stackexchange.com/questions/145437/why-use-an-interface-when-the-class-can-directly-implement-the-functions