Pass data/bundle using navigateUp in Android Navigation Component

Question

I found the question but does not have solution in code

I want to have data when backpress/manual back happens. I am using navigateUp() to go back. How

Answer 1

You can use the following simple implementation to pass data after popBackStack() with Android Navigation Component. This approach is based on official Google documentation

You just need to extend your fragments with BaseFragment and use the following methods:

//to start Fragment2 for result
startFragmentForResult(actionId: Int)

//to perform pop back stack in Fragment2
popBackStackWithResult(result: Any)

//to observe your result in Fragment1
onFragmentResult(result: Any)

1. Add SharedViewModel class

   class SharedViewModel : ViewModel() {
       val sharedData = MutableLiveData()
   
       fun share(obj: Any) {
           sharedData.value = obj
       }
   }
   

2. Add BaseFragment class

   import androidx.fragment.app.Fragment
   
   abstract class BaseFragment : Fragment() {
   
   protected var rootView: View? = null
   
   private var sharedViewModel: SharedViewModel? = null
   
   override fun onCreateView(
       inflater: LayoutInflater,
       container: ViewGroup?,
       savedInstanceState: Bundle?
   ): View? {
       if (rootView == null) {
           rootView = inflater.inflate(getLayoutId(), container, false)
           initSharedViewModel()
       }
       return rootView
   }
   
   abstract fun getLayoutId()
   
   open fun onFragmentResult(result: Any){
       //TODO implement in descendants
   }
   
   protected fun startFragmentForResult(actionId: Int){
       findNavController().navigate(actionId)
   }
   
   protected fun popBackStackWithResult(result: Any){
       findNavController().popBackStack()
       sharedViewModel?.share(result)
   }
   
   private fun initSharedViewModel() {
       sharedViewModel = ViewModelProvider(activity!!).get(SharedViewModel::class.java)
   
       sharedViewModel?.sharedData?.observe(activity!!, object : Observer {
           override fun onChanged(params: Any) {
               onFragmentResult(params)
           }
       })
   }    
   }
   

3. Add Fragment1

   class Fragment1 : BaseFragment(){
       override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
           super.onViewCreated(view, savedInstanceState)
   
           some_btn.setOnClickListener{
               startFragmentForResult(R.id.action_fragment1_to_fragment2)
           }
       }
   
       override fun onFragmentResult(result: Any) {
           if(result is AnyYourClass){
               //PERFECT! DO SOMETHING WITH YOUR RESULT
           }
       }
   }
   

4. Add Fragment2

   class Fragment2 : BaseFragment(){
       override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
           super.onViewCreated(view, savedInstanceState)
   
           some_btn.setOnClickListener{
               popBackStackWithResult(AnyYourClass())
           }
       }            
   }
   

Cheers ;)