Calling a fragment method from activity with navcontroller

Android
1

I am currently developing an Android NFC application. This application contains a NavigationDrawer in which I can access 3 different fragments which each correspond to 3 different NFC features.

My goal is that when the onNewIntent method is called, so when the NFC tag is detected, I update the UI with the information in the tag.

Because of the navController, I can’t use the supportFragmentManager.findFragmentById method directly, otherwise I would get a NullPointerException. So I tried to use the navController.currentDestination method but the value returned is null too. What can I do?

updateUI() method in MainActivity class:

private fun updateUI() {
    val navController = findNavController(R.id.nav_host_fragment)
    val fragment = navController.currentDestination as? MemoryFragment
    fragment?.setManufacturerValue((nfcManufacturer.getValue(tag!!.id[6].toInt())))
}

MemoryFragment class:

class MemoryFragment : Fragment() {

    private lateinit var memoryViewModel: MemoryViewModel

    override fun onCreateView(
            inflater: LayoutInflater,
            container: ViewGroup?,
            savedInstanceState: Bundle?
    ): View? {
        memoryViewModel = ViewModelProvider(this).get(MemoryViewModel::class.java)
        val root = inflater.inflate(R.layout.fragment_memory, container, false)

        val icManuf: TextView = root.findViewById(R.id.ic_manufacturer_value)
        memoryViewModel.icManufacturer.observe(viewLifecycleOwner, Observer {
            icManuf.text = it
        })
        return root
    }

    fun setManufacturerValue(icManufacturer: String) {
        memoryViewModel.setManufacturer(icManufacturer)
    }
}

MemoryViewModel class:

class MemoryViewModel : ViewModel() {
    // The current IC Manufacturer
    private val _icManufacturer = MutableLiveData<String>()

    val icManufacturer: LiveData<String>
        get() = _icManufacturer

    init {
        _icManufacturer.value = ""
    }

    fun setManufacturer(value: String) {
        _icManufacturer.value = value
    }
}
2

Just an idea, but you can use activityViewModel to share data between activity and fragment, in that way you don’t need reference to fragment.