How to access a fragment method from a class which is passed to it as a context

Question

I have 3 fragments which are shown using add tab methods in the main activity.

tablayout.addTab(one)
tablayout.addTab(two)
tablayout.addTab(three)

I have a non activity class operations which is passed the context of the fragments when ever it is called. The class operations will performs actions for the three fragments.

Operations op = new Operations(getActivity, list, emptyList, recyclerView)

The first parameter getActivity is the context of the calling fragment.

Fragment 1 has a method showMessage1 Fragment 2 has a method showMessage2 Fragment 3 has a method showMessage3

HOW CAN I CALL ANY ONE OF THESE METHODS FROM OPERATIONS CLASS WHICH IS HAVING THE CONTEXT OF ONE OF THESE FRAGMENTS?

Answer 1

you need to cast context to your Fragment class

Example, inside your Operations class, you need to cast your context to Fragment 1

When you need to call Fragment1's Method

(context as Fragment1).showMessage1()

When you need to call Fragment2's Method

(context as Fragment2).showMessage2()

Answer 2

The main problem in this situation is high-coupling. If you separate your logic in two classes: Fragment and Operations and Fragment knows about Operations and Operations knows about Fragment it is not good at all. Let Operations depend on an abstraction.

Create an interface and make each of your fragments to implement it.

MessageDisplay.java

interface MessageDisplay { void showMessage(); }

Fragment1.java

class Fragment1 implements MessageDisplay { }

Fragment2.java

class Fragment2 implements MessageDisplay { }

Fragment3.java

class Fragment3 implements MessageDisplay { }

Fragment1.java

Operations op = new Operations(getActivity(), this, list, .... );

Operations.java

class Operations {
    ....
    private MessageDisplay messageDisplay;
    ....
    public Operations(Activity activity, MessageDisplay messageDisplay, ...) {
        ....
        this.messageDisplay = messageDisplay;
        ....
    }

    public void methodWithYourCustomLogic(){
        ....
        messageDisplay.showMessage();
    }
}