List all ways of data transfer between fragments.

Bundle arguments: The most common method. Data is passed via a Bundle through the fragment's setArguments() method.

// In the sender fragment
val bundle = Bundle()
bundle.putString("key", "value")
val targetFragment = TargetFragment()
targetFragment.arguments = bundle
// ... transition to TargetFragment

// In the receiver fragment
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val value = arguments?.getString("key")
    // ... use the value
}

Shared ViewModel: Used for passing data related to the activity's or multiple fragments' lifecycle.

// In ViewModel
class SharedViewModel : ViewModel() {
    val data = MutableLiveData<String>()
}

// In both fragments
private val sharedViewModel: SharedViewModel by activityViewModels()

// In the sender fragment
sharedViewModel.data.value = "data to pass"

// In the receiver fragment
sharedViewModel.data.observe(viewLifecycleOwner) { data ->
    // ... use the data
}

Callback Interfaces: The fragment can define an interface implemented by the activity. The fragment calls methods of this interface, passing data to the activity, which can then pass it to another fragment.

// Interface in the sender fragment
interface OnDataPass {
    fun onDataPass(data: String)
}

// Sender fragment
private var dataPasser: OnDataPass? = null

override fun onAttach(context: Context) {
    super.onAttach(context)
    if (context is OnDataPass) {
        dataPasser = context
    } else {
        throw RuntimeException("$context must implement OnDataPass")
    }
}

fun passData(data: String) {
    dataPasser?.onDataPass(data)
}

// Activity
class MainActivity : AppCompatActivity(), OnDataPass {
    override fun onDataPass(data: String) {
        val targetFragment = supportFragmentManager.findFragmentById(R.id.target_fragment) as? TargetFragment
        targetFragment?.updateData(data) // Assumes method updateData in TargetFragment
    }
}

// Receiver fragment
fun updateData(data: String) {
    // ... update UI or save data
}

Fragment Result API: A modern way to pass results between fragments, introduced in AndroidX Fragment version 1.3.0.

// In the sender fragment
setFragmentResult("requestKey", bundleOf("bundleKey" to "result"))

// In the receiver fragment
setFragmentResultListener("requestKey") { requestKey, bundle ->
    val result = bundle.getString("bundleKey")
    // ... use the result
}