BaseAdapter notifyDatasetChanged() called but getView() is never called

Question

I have a custom adapter that visualize each row in the list of Orders.

public class OrderRowAdapter extends BaseAdapter implements OnClickListener {
    OrderList items_;
    LayoutInflater inflater_;
    int list_view_resource_id_;
    private final String TAG = "OrderRowAdapter";

    public OrderRowAdapter(Context context, int list_view_resource_id,
            OrderList items) {
        this.list_view_resource_id_ = list_view_resource_id;
        this.items_ = items;
        this.inflater_ = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public Object getItem(int position) {
        return items_.getOrders(position);
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        Log.d(TAG, "View updated for item in position = " + position);

        View v = convertView;
        if (v == null) {
            v = inflater_.inflate(list_view_resource_id_, parent);
        }

        Order item = items_.getOrders(position);
        if (item != null) {
            TextView order_info_tv = (TextView) v.findViewById(R.id.order_info);
            TextView order_status_tv = (TextView) v.findViewById(R.id.order_status);

            if (order_info_tv != null) {
                order_info_tv.setText(
                        String.format("For customer: %s\nTotal of %d items", item.getCustomerId(), item.getItemsCount()));
            }
            if (order_status_tv != null) {
                order_status_tv.setText("Status: " + getStatusText(item.getStatus()));
            }
        }
        return v;
    }

    public int getCount() {
        if (items_ == null) {
            Log.d(TAG, "Null so get count returned 0");
            return 0;
        } else {
            Log.d(TAG, "Get count returned " + items_.getOrdersCount());
            return items_.getOrdersCount();
        }
    };

After querying new list of orders from a web service, I want to update the content of the ListView, so I have my Activity does the updating before calling notifyDataSetChanged()

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.orders);

    initThreading();
    findViews();
    setUrls();

    // Load the list of order from disk
    try {
        order_list_ = OrderList.parseFrom(new FileInputStream(
                "/sdcard/orderList.bin"));
    } catch (FileNotFoundException e) {
        Log.e(TAG, "Cannot find the file", e);
    } catch (IOException e) {
        Log.e(TAG, "Cannot read the file", e);
    }

    order_row_adapter_ = new OrderRowAdapter(OrderActivity.this,
            R.layout.order_row, order_list_);
    orders_listview_.setAdapter(order_row_adapter_);

    // Request new updates from the server
    updateOrderInformation(-1);
}

public void updateOrders(InputStream new_order_stream) {
    Log.d(TAG, "Updating order UI");
    try {
        order_list_.parseFrom(new_order_stream);
    } catch (IOException e) {
        Log.e(TAG, "IOException" , e);
    }

    runOnUiThread(new Runnable() {
        public void run() {
            guiUpdateOrders();
        }
    });
}

private void guiUpdateOrders() {
    order_row_adapter_.notifyDataSetChanged();
    Log.d(TAG, "Dataset notified that it has changed. GUI update anytime now.");
}

But, the getView() method of OrderRowAdapter is never called. The ListView is never updated.

Answer 1

It turns out the problem with my getView() not being called is because it is not visible. My layout xml has the upper TextView with fill_parent for its height. Thus the entire view only has that single TextView visible.

Solution: check the graphical view of the layout in question to make sure the ListView is visible.

Answer 2

Make sure BaseAdapter methods

registerDataSetObserver(DataSetObserver observer) 
unregisterDataSetObserver(DataSetObserver observer) 

are not overridden.

Answer 3

To change the content of your ListView, you must keep using the same reference to the List. Here you're creating another list and assigning it to the items_ variable (which does not contain the list itself, it's just a place to store a reference to a List), but your View still has a reference to the old list.

Instead of items_ = new_order_list this should work :

items_.clear();
items_.addAll(new_order_list);

EDIT :

To explain it better, try to create a new variable named old_items :

public void setNewOrderList(List<Order> new_order_list)
{
    Log.d(TAG, "New Order List available. Num items = " + new_order_list.size());

    List<Order> old_items = items_; // store the reference to the old list
    items_ = new_order_list;

    Log.d(TAG, "items_.size() = " + items_.size());
    Log.d(TAG, "old_items.size() = " + old_items.size()); // The old list still exists, and it's the one used by your ListView

    notifyDataSetChanged();
}