Listview refresh without notifyDataSetChange

Question

There is a problem with notifyDataSetChanged. I have a list which retrieves data from sqlite database. The problem is that I know that I have to call notifyDataSetChanged everytime I use add method of list class. I can't understand why my list shows data after addAll() calling without the notifyDataSetChange(). I also tried using add() but result is the same. I need answer because I want to understand very well how notifyDataSetChange() works. Fragment code:

 public static List<Wherehouse> mListFoodsIn;  
wherehouseAdapter wherehouseAdapter;



@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View v = inflater.inflate(R.layout.fragment_wherehouse, container, false);

    wherehouseList = v.findViewById(R.id.wherehouseList); 
    final DBManager db = new DBManager(getActivity());

    mListFoodsIn = new ArrayList<>();
    wherehouseAdapter = new wherehouseAdapter(getActivity(), mListFoodsIn);
    new GetWherehoouseAsync(getActivity(),mListFoodsIn, wherehouseList, wherehouseAdapter).execute();  
    wherehouseList.setAdapter(wherehouseAdapter);

Async class:

public static class GetWherehoouseAsync extends AsyncTask<Void, Void, Void>{

    Context mContext;
    wherehouseAdapter mAdapter;
    DBManager db;
    List<Wherehouse> mList;

    ListView listViewWherehouse;

    public GetWherehoouseAsync(Context mContext, List<Wherehouse> list, ListView lv, wherehouseAdapter adapter) {
        this.mContext = mContext;
        db = new DBManager(mContext);
        this.mList = list;
        this.listViewWherehouse = lv;
        mAdapter = adapter;
    }


    @Override
    protected void onPreExecute() {
        super.onPreExecute();


    }

    @Override
    protected Void doInBackground(Void... voids) {

      //  List<Wherehouse> tmpList = db.GetWherehouse();


        mList.addAll(db.GetWherehouse());


        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);

      //  mAdapter.notifyDataSetChanged();
    }

It maybe natural scenario because I call async() in onCreateView?

`public static List mListFoodsIn;` everything involving this is bound to be wrong and/or cause crashes later. Including multi-threading problems. — EpicPandaForce, Nov 17 '19 at 01:39

score 0 · Accepted Answer · answered Nov 16 '19 at 20:44

0

You're applying the adapter to your listview after updating the list mListFoodsIn, since your data is coming from a Database not via a network call the result returns relatively fast. So the correct list is applied to the listview on creation correctly. If the data were to change during the lifecycle of your fragment, then you would need to notify the adapter.

notifyDataSetChanged()

Notifies the attached observers that the underlying data has been changed

answered Nov 16 '19 at 20:44

JakeB

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But I also tried to apply the adapter to my listview before updating the list but behaviour is the same. Is it normal? – Francesco Caputo Nov 16 '19 at 21:58
Calling ```setAdapter``` will update the listview, however if you call this repeatadly it will create new adapters consuming memory until the previous ones are garbage collected. When you set the adapter it calls through to ```requestLayout()``` which resets the view and the data in this case. Here is a good example of the view lifecycle https://stackoverflow.com/a/25846243/5644761 – JakeB Nov 16 '19 at 23:20
It could be timing, the list is updated from the async before setting the adapter finishes. – JakeB Nov 16 '19 at 23:48
Thanks very much JakeB, now everything is a little bit clearer. – Francesco Caputo Nov 17 '19 at 16:59

Listview refresh without notifyDataSetChange

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