How refresh ListView?

Question

I'm starting in the Kotlin/Java for android.

I read an external database and refresh the local database from the info I read.

I display my database information in a ListView without worries but I would have liked to refresh it with the click of a button. I correctly retrieve the external database and update it correctly but the ListView doesn't refresh and crashes if I click on it. However if I change screen and come back it works correctly and is refreshed.

Could someone please tell me how to properly update the ListView?

I was unable to get "notifydatasetchanged ()" to work.

Thanks for help

class HomeFragment : Fragment() {

private lateinit var homeViewModel: HomeViewModel
private lateinit var accesLocal : AccesLocal

@SuppressLint("UseRequireInsteadOfGet")
override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
): View? {
    homeViewModel =
            ViewModelProvider(this).get(HomeViewModel::class.java)
    val root = inflater.inflate(R.layout.fragment_home,container,false)
    
    accesLocal = AccesLocal(getActivity()?.getApplicationContext())
    val ButtonRefresh: Button= root.findViewById(R.id.Refresh_list)
    val ButtonNumber: Button= root.findViewById(R.id.BoutonNombre)
    val textView: TextView = root.findViewById(R.id.text_home)
    val ListeQuestion:ListView = root.findViewById(R.id.ListeQuestion)

    if(accesLocal.number==0) {accesLocal.ajout(Question("Qu'est ce que cette app ?", 1))}
    homeViewModel.text.observe(viewLifecycleOwner, Observer {textView.text = it})
    
    ListeQuestion.setBackgroundColor(Color.GRAY)
    ListeQuestion.adapter = getActivity()?.baseContext?.let { Adaptateur -> MyCustomAdapter(Adaptateur) }

    ButtonRefresh.setOnClickListener { 
        view ->Snackbar.make(view,"Lecture base de donnée, wait", Snackbar.LENGTH_LONG).setAction("Action", null).show()
        accesLocal= AccesLocal(getActivity()?.getApplicationContext())

        val registrationForm1 : JSONObject =  JSONObject()
        try {registrationForm1.put("subject", "lire_tous");}
        catch (e: JSONException) {e.printStackTrace();}

        val body: RequestBody = RequestBody.create(
                MediaType.parse("application/json; charset=utf-8"),
                registrationForm1.toString()
        );
        RequestSynchro(root, "http://ns328061.ip-37-187-112.eu:5000", body);     //<-Refresh my local database 
        
        ListeQuestion.adapter = activity?.let { MyCustomAdapter(it.applicationContext) }    //Dont works for refresh my list view
    }

    ButtonNumber.setOnClickListener {
        val registrationForm1 : JSONObject =  JSONObject()
        try {registrationForm1.put("subject", "nombre");}
        catch (e: JSONException) {e.printStackTrace();}

        val body: RequestBody = RequestBody.create(
                MediaType.parse("application/json; charset=utf-8"),
                registrationForm1.toString()
        );

        view?.let { it1 -> Snackbar.make(it1, "Post creation body, wait", Snackbar.LENGTH_LONG).setAction(
                "Action",
                null
        ).show() }
        RequestNumber(root, "http://ns328061.ip-37-187-112.eu:5000", body);
    }
    return root
}

My adapter :

    private class MyCustomAdapter(context: Context): BaseAdapter() {

    private val mContext: Context
    private lateinit var accesLocal : AccesLocal

    init {
        this.mContext = context
    }

    override fun getCount(): Int {
        accesLocal = AccesLocal(mContext)
        return accesLocal.number
    }

    override fun getItemId(position: Int): Long {
        return position.toLong()
    }

    override fun getItem(position: Int): Any {
        return "TEST STRING"
    }

    override fun getView(position: Int, convertView: View?, viewGroup: ViewGroup?): View {
        val textView = TextView(mContext)
        accesLocal = AccesLocal(mContext)
        textView.text = "Question numero "+(position+1)+"->\""+accesLocal.recupNumero(position + 1)+"\""
        return textView
    }
}

Answer 1

I would suggest using RecyclerView instead of ListView. Also, you can create a method in your adapter which would take the list of data and set it and use notifydatasetchanged there.