在Android中的片段上更新listView

Question

I can't get a listView updated on Android. I have a fragment with a listView, and its items are returned by a REST call.

Here is the AsyncTask:

 private class GetMenuPizzeria extends AsyncTask<String, Void, Object[]> {
    private final SelectPizzaFragment.ContentAdapter mListAdapter;
    private final Context appContext;
    private final String pizzeriaId;

    private GetMenuPizzeria(ContentAdapter mListAdapter, Context appContext, String id) {
        this.mListAdapter = mListAdapter;
        this.appContext = appContext;
        this.pizzeriaId = id;
    }

    @Override
    protected Object[] doInBackground(String... params) {
            return pizzeriaManager.getMenuPizzeria(pizzeriaId).toArray();
    }

    @Override
    protected void onPostExecute(Object[] result) {
        mListAdapter.updateItems(result, appContext);
    }
}

and here is the function called onPostExecute (updateItems) :

public void updateItems(Object[] newItems, Context appContext) {

            PizzaMenu pm;

            lPizzaNames.clear();
            lPizzaDesc.clear();
            lPizzaPrices.clear();

            Resources resources = appContext.getResources();
            TypedArray a = resources.obtainTypedArray(R.array.place_avator);

            for (int i = 0; i < newItems.length; i++) {
                pm = (PizzaMenu) newItems[i];
                lPizzaNames.add(pm.getName());
                lPizzaDesc.add(pm.getIngredients());
                lPizzaPrices.add(pm.getPrice());
                lPlaceAvators.add(a.getDrawable(0));
            }
            this.notifyDataSetChanged();
    }

Then, I call the AsyncTask like that:

GetMenuPizzeria getMenuPizzeria = new GetMenuPizzeria(adapter, this.getContext(), id);
getMenuPizzeria.execute();

and that works when I call it the first time, inside the onCreateView of my fragment. The problem is, I have to update the list every time the selected pizzeria changes, so I wrote a method:

public void updatePizzeriaMenu(String idPizzeria) {
    GetMenuPizzeria getMenuPizzeria = new GetMenuPizzeria(new ContentAdapter(recyclerView.getContext()), this.getContext(), idPizzeria);
    getMenuPizzeria.execute();
}

That method correctly calls the AsyncTask and I don't get any errors, except the list is not updated (but notifyDataSetChanged() is called and onBindViewHolder is called as well). I suppose the way I'm retrieving the adapter is wrong or something like that because seems like the list I'm populating everytime I call updatePizzeriaMenu is empty. Could someone please help me and tell me what I'm missing? Thanks in advance

EDIT: here is my adapter class :

public static class ContentAdapter extends RecyclerView.Adapter<ViewHolder> {


    private final List<String> lPizzaNames = new ArrayList<String>();
    private final List<String> lPizzaDesc = new ArrayList<String>();
    private final List<String> lPizzaPrices = new ArrayList<String>();

    private final List<Drawable> lPlaceAvators = new ArrayList<Drawable>();

    public ContentAdapter(Context context) {
        Resources resources = context.getResources();
        TypedArray a = resources.obtainTypedArray(R.array.place_avator);
        a.recycle();
    }


    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new ViewHolder(LayoutInflater.from(parent.getContext()), parent);
    }

    public void updateItems(Object[] newItems, Context appContext) {
        //see above....
    }


    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.avator.setImageDrawable(lPizzaAvators.get(position % lPizzaAvators.size()));
        holder.name.setText(lPizzaNames.get(position % lPizzaNames.size()));
        holder.description.setText(lPizzaDesc.get(position % lPizzaDesc.size()));
        holder.price.setText(lPizzaPrices.get(position % lPizzaPrices.size()));
    }



    @Override
    public int getItemCount() {
        return lPizzaPrices.size();
    }



}

Answer 1

You are creating new adapters each time in updatePizzeriaMenu(String idPizzeria) method. but i think, those adapters is not related to any recyclerView through recyclerView.setAdapter() method. So do not create new ContentAdapter each time instead pass the previous adapter object.

public void updatePizzeriaMenu(String idPizzeria) {
    GetMenuPizzeria getMenuPizzeria = new GetMenuPizzeria(adapter, this.getContext(), idPizzeria);
    getMenuPizzeria.execute();
}

As you are clearing previous data

lPizzaNames.clear();
lPizzaDesc.clear();
lPizzaPrices.clear();

and updating new data, it should work fine.

Answer 2

you haven't updated the adapter in this method, you are assigning some values to some variables, and it doesn't seem to be those variables having any relationship with adapter, you have to set Object in adapter!

for example,

 this.setPizzaMenuList(pizzaMenuList); 
 this.notifyDataSetChanged)();

will update the ListView.and

lpizzaMenuList= pizzaMenuList;
this.notifyDataSetChanged)();

won't update the ListView!