What methods are used for interaction between Fragments in the same Activity?

Interaction between fragments within the same Activity is usually implemented through the Activity acting as a mediator. Main methods:

1. Using a callback interface

   • The fragment declares an interface with methods for data transfer.
   • The Activity implements this interface and receives data from one fragment.
   • The Activity passes data to another fragment.

2. Using ViewModel with Activity lifecycle (Shared ViewModel)

   • A ViewModel is created, associated with the Activity.
   • Both fragments access the same ViewModel.
   • Fragments exchange data via LiveData or other observable objects.

3. Using FragmentManager to find fragments and call their methods directly

   • Less preferred method, as it increases coupling.

Example with interface:

// In Fragment A
interface OnDataPass {
    fun onDataPass(data: String)
}

class FragmentA : Fragment() {
    lateinit var dataPasser: OnDataPass

    override fun onAttach(context: Context) {
        super.onAttach(context)
        dataPasser = context as OnDataPass
    }

    fun passData() {
        dataPasser.onDataPass("Hello from FragmentA")
    }
}

// In Activity
class MainActivity : AppCompatActivity(), FragmentA.OnDataPass {
    override fun onDataPass(data: String) {
        val fragmentB = supportFragmentManager.findFragmentById(R.id.fragmentB) as FragmentB
        fragmentB.updateData(data)
    }
}