How to send data of three fragments to single activity?

Question

I have a question more simple, but I can't find answers about it on the internet. Here's the deal: I have three fragments and I need to send data of each fragment to a single activity and then to open another activity. I intend to use an interface to do that. So, I need to create three interfaces one to each fragment and implements them on activity? I have three implementations getting data for each activity? Before doing the codes, I need about it. Thanks in advance.

Demo image

Answer 1

First, let's create an interface.

interface MyInterface {
     fun onSomethingDone(someData: Int)  //A sample function, you can customize it your needs.
 }

Then

override onAttachFragment in your activity like this. Always remember this rule, never tightly couple a fragment to an activity. So, what you can do is to check the fragment and do relevant operations like this:

class MyActivity : AppCompatActivity() {

    override onAttachFragment(fragment: Fragment) {

           when (fragment) { //A switch statement, checking using instanceOf() in Java.
             is Fragment1 -> fragment.firstFragmentListener = this //Proviving context of your activity to public variable of each fragment.
             is Fragment2 -> fragment.secondFragmentListener = this
             is Fragment3 -> fragment.thirdFragmentListener = this
         }
     }
 }

This will ensure that you are not tightly coupling the fragment like casting it the context of a specific activity while setting up your custom listener.

Lets move to fragments

 class Fragment1 : Fragment() {

     var firstFragmentListener: MyInterface? =  null  //public member, we are accessing it in our activity method, look above! 

      override onCreate() {

          myButton.setOnClickListener {
              firstFragmentListener.onSomethingDone(999) // Just sending random integer as the method parameter.
           }
       }
  }

This one sample fragment class should give you enough idea on how this is being set up. Just the way this fragment class is implemented, you can do the same with Fragment2, and Fragment3.

Back to our activity

But this time, we will implement a listener method.

class MyActivity : AppCompatActivity(), MyInterface {

   override fun onSomethingDone(someData: Int) {
      when (someData) {
         999 -> //Came from first fragment
         1000 -> //Second fragment
         1001 -> //Third fragment
      }
    }

    override onAttachFragment(fragment: Fragment) {

           when (fragment) { //A switch statement, checking using instanceOf() in Java.
             is Fragment1 -> firstFragmentListener = this //Proviving context of your activity to public variable of each fragment.
             is Fragment2 -> secondFragmentListener = this
             is Fragment3 -> thirdFragmentListener = this
         }
     }
 }

This is about it, I will hook up a link to give you a wild idea. Single interface for multiple fragments. While ViewModel is a part of the second generation Android development and offers various advantages not just intercommunication between fragments and an activity.

Answer 2

You could create one seperate interface via New > Java Class and then simply choose Kind > Interface in the dialog. Then you add the methods you need to the Interface and let your Activity implement it. After doing so you go to your Fragments and get an instance of that Interface in the onAttach(Context context) method like this:

    @Override
    public void onAttach(@NonNull Context context)
    {
        Log.d(TAG, "onAttach:true");

        super.onAttach(context);

        if (context instanceof OnFragmentInteractionListener)
        {
            mFragmentInteractionListener = (OnFragmentInteractionListener) context;
        }
        else
        {
            throw new RuntimeException(context.toString() + " must implement OnFragmentInteractionListener");
        }
    }

Now you can call the Interfaces methods by saying mFragmentInteractionListener.deleteInternet(true) anywhere in your Fragment class for example.

If you have any further questions, just let me know in the comments.