calling BaseAdapter's notifyDataSetChanged() inside CustomAdapter not refreshing ListView

Question

I have ArrayList<MyObject> data which is populated on the ListView using a CustomAdapter.

I've implemented View.OnClickListener in the CustomAdapter class and clicking a button deletes the particular row. After deleting the row, both from database and from the data object using data.remove(i) inside the Custom Adapter, I call notifyDataSetChanged().

Problem is that it does not refresh teh ListView.

I'm using a tabbed activity with fragment. So, when go to some distant tab and come back to this tab, it refreshes the ListView and the deleted item does not show anymore.

Why is the ListView not refreshing immediately when i call notifyDataSetChanged() but changing when i move to another fragment and back?

My CustomAdapter class is as follows:

public class CustomAdapter extends BaseAdapter implements View.OnClickListener {

    private LayoutInflater mInflater;
    Context context;
    private ArrayList<MyObject> data;

    public CustomAdapter(Context context, ArrayList<MyObject> data) {
        mInflater = LayoutInflater.from(context);
        this.data = data;
        this.context = context;
    }
    .....
    .....
    .....
    .....
    .....

    @Override
    public void onClick(View v) {
        DataBaseHelper db = new DataBaseHelper(context);
        int id = data.get((Integer) v.getTag()).id;
        //use getTag() to get the position, set position in tag before adding listener.
        switch (v.getId()){
            case R.id.txtName:
                Toast.makeText(context, "Show Details" + v.getTag(), Toast.LENGTH_SHORT).show();
                break;
            case R.id.btnRemove:
                db.removePaper(id); // works fine
                data.remove(v.getTag()); // works fine
                notifyDataSetChanged(); // PROBLEM HERE: Does not refresh listview
                break;
            case R.id.btnFavorite:
                Toast.makeText(context, "Favorite" + v.getTag(), Toast.LENGTH_SHORT).show();
                break;

        }

    }
}

After deleting the data (row) reload list from db or set data again to listView. — Sohail Zahid, Feb 07 '16 at 12:10
@SohailZahid I know that will work. I am not looking for a workaround. I want to know why the `notifyDataSetChanged()` isn't refreshing the list. — Viral Patel, Feb 07 '16 at 12:11
no it does not. `data.remove(v.getTag());` removes the element from data object. — Viral Patel, Feb 07 '16 at 12:13
after deleting you have to again set your adapter with deleted data. — Sohail Zahid, Feb 07 '16 at 12:19
i think you have not understood the problem. The data changes inside the adapter itself, not outside. I dont think the same thing needs to be reassigned within the CustomAdapter class. — Viral Patel, Feb 07 '16 at 12:22
Thats why i ask you this before. try this context.notifyDataSetChanged() will solve your problem. — Sohail Zahid, Feb 07 '16 at 12:27
your data model is sqlite db based, right? so use `SimpleCursorAdapter`, not a custom one — pskink, Feb 07 '16 at 12:28
@SohailZahid that method is not in the Context class. cannot be called using context object. :-) — Viral Patel, Feb 07 '16 at 12:30
@pskink context is just used here for referencing here because you are in onClick. — Sohail Zahid, Feb 07 '16 at 12:33

score 2 · Accepted Answer · edited Feb 07 '16 at 13:02

I had a similar issue some time ago, I fixed it extending ArrayAdapter<MyObject> instead of BaseAdapter and overriding some methods:

public class CustomAdapter extends ArrayAdapter<MyObject> {

private List<MyObject> list = new ArrayList<MyObject>();

public CustomAdapter(Context context, int resource) {
    super(context, resource);
}

 @Override
 public void add(MyObject obj) {
     this.list.add(obj);
     super.add(obj);
 }

 @Override
 public void remove(MyObject obj) {
     int i = getPosition(obj);
     if(i >= 0)
         list.remove(i);
     super.remove(obj);
 }

 @Override
 public void clear() {
     this.list.clear();
     super.clear();
 }

 @Override
 public MyObject getItem(int position) {
     return this.list.get(position);
 }

 @Override
 public int getPosition(MyObject obj) {
     for(int i = 0; i < list.size(); i++) {
         if(list.get(i).equals(obj))
             return i;
     }
     return -1;
 }}

Then call these methods instead of calling directly methods of your List.

calling BaseAdapter's notifyDataSetChanged() inside CustomAdapter not refreshing ListView

1 Answers1

Linked