Update data in Arrayadapter

Question

i have this problem, i have

private ArrayList<CustomItem> items; 
private ArrayAdapter<CustomItem> arrayAdapter;

i show the data present in items, this data i see in listview, now i want to update data and see this new data

if (!items.isEmpty()) {
    items.clear(); // i clear all data
    arrayAdapter.notifyDataSetChanged(); // first change
    items = getNewData();// insert new data and work well
    arrayAdapter.notifyDataSetChanged();  // second change                                      
}

in the first change i see the data are cleaned, but in second change i don't see the new data in listview, i check and the item don't empty

i don't know where is the error, can you help me? best regads Antonio

Are you confident that getNewData() is returning a list that contains something? — nicholas.hauschild
– nicholas.hauschild, Commented Jul 25, 2012 at 21:16
Please post getNewData(), also you only need to call arrayAdapter.notifyDataSetChanged(); once at the end. — Sam
– Sam, Commented Jul 25, 2012 at 21:19

metalwihen · Accepted Answer · 2015-11-24 09:37:11Z

19

This is how I update the Adapter with new data:

            if (arrayAdapter == null) {
                arrayAdapter = new CustomArrayAdapter(getActivity(), data);
                listview.setAdapter(userAutoCompleteAdapter);
            } else {
                arrayAdapter.clear();
                arrayAdapter.addAll(newData);
                arrayAdapter.notifyDataSetChanged();
            }

answered Nov 24, 2015 at 9:37

metalwihen

1,0839 silver badges9 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

HomeIsWhereThePcIs Over a year ago

ArrayAdapter.addAll() already calls notifyDataSetChanged(). So you are actually calling notifyDataSetChanged() twice here.

azgolfer · Accepted Answer · 2012-07-25 21:19:07Z

13

Assuming the getNewData() function returns ArrayList<CustomItem>, can you change the line:

items=getNewData();

to

items.addAll(getNewData());

and see if that works?

answered Jul 25, 2012 at 21:19

azgolfer

15.1k4 gold badges51 silver badges46 bronze badges

Comments

Sam Chen · Accepted Answer · 2019-08-23 15:11:24Z

The ArrayList you created in Activity class is an reference variable, which is holding the same reference to the ArrayList in your Adapter class by passing through the constructor (when you initialize the Adapter object).

However, by executing items = getNewData(), you're assigning a new reference to the items in your Activity class, the reference in your Adapter class remains the same, thus you see no changes on the screen.

It's like this:

personA: the ArrayList object in Activity class

personB: the ArrayList object in Adapter class

PersonA and personB they are both holding a map of USA (separately), and the screen shows personB's map. Then someone replaces the map of personA with another coutry's map. Guess what, the screen still shows USA map.

Instead of changing the reference of items, you should use add(), remove(), clear() or addAll() to modify the items's data then call notifyDataSetChanged().

Collectives™ on Stack Overflow

Update data in Arrayadapter

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related