Is there a method that works like start fragment for result?

Solution 1:

All of the Fragments live inside Activities. Starting a Fragment for a result doesn't make much sense, because the Activity that houses it always has access to it, and vice versa. If the Fragment needs to pass on a result, it can access its Activity and set its result and finish it. In the case of swapping Fragments in a single Activity, well the Activity is still accessible by both Fragments, and all your message passing can simply go through the Activity.

Just remember that you always have communication between a Fragment and its Activity. Starting for and finishing with a result is the mechanism for communication between Activities - The Activities can then delegate any necessary information to their Fragments.

Solution 2:

If you wish, there are some methods for communication between Fragments,

setTargetFragment(Fragment fragment, int requestCode)
getTargetFragment()
getTargetRequestCode()

You can callback using these.

Fragment invoker = getTargetFragment();
if(invoker != null) {
    invoker.callPublicMethod();
}

Solution 3:

Recently, Google has just added a new ability to FragmentManager which made the FragmentManager be able to act as a central store for fragment results. We can pass the data back and forth between Fragments easily.

You can out the blog post that I've made https://oozou.com/blog/starting-a-fragment-for-results-in-android-46

Starting fragment.

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    // Use the Kotlin extension in the fragment-ktx artifact
    setResultListener("requestKey") { key, bundle ->
        // We use a String here, but any type that can be put in a Bundle is supported
        val result = bundle.getString("bundleKey")
        // Do something with the result...
    }
}

A Fragment that we want the result back.

button.setOnClickListener {
    val result = "result"
    // Use the Kotlin extension in the fragment-ktx artifact
    setResult("requestKey", bundleOf("bundleKey" to result))
}

The snippet is taken from Google's official documents. https://developer.android.com/training/basics/fragments/pass-data-between#kotlin

At the date of this answer written, this feature is still in alpha state. You can try it out using this dependency.

androidx.fragment:fragment:1.3.0-alpha05

Solution 4:

We can simply share the same ViewModel between fragments

SharedViewModel

import android.arch.lifecycle.MutableLiveData
import android.arch.lifecycle.ViewModel

class SharedViewModel : ViewModel() {

    val stringData: MutableLiveData<String> by lazy {
        MutableLiveData<String>()
    }

}

FirstFragment

import android.arch.lifecycle.Observer
import android.os.Bundle
import android.arch.lifecycle.ViewModelProviders
import android.support.v4.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup

class FirstFragment : Fragment() {

    private lateinit var sharedViewModel: SharedViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        activity?.run {
            sharedViewModel = ViewModelProviders.of(activity).get(SharedViewModel::class.java)
        }
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_first, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        sharedViewModel.stringData.observe(this, Observer { dateString ->
            // get the changed String
        })

    }

}

SecondFragment

import android.arch.lifecycle.ViewModelProviders
import android.os.Bundle
import android.support.v4.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGrou

class SecondFragment : Fragment() {

    private lateinit var sharedViewModel: SharedViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        activity?.run {
            sharedViewModel = ViewModelProviders.of(activity).get(SharedViewModel::class.java)
        }
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_first, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        changeString()
    }

    private fun changeString() {
        sharedViewModel.stringData.value = "Test"
    }

}