Refresh listview data from custom ArrayAdapter which is populated by SQLite Database

Question

I have a custom ArrayAdapter which is set to a listview with data from database:

CustomAdapter adapter = new CustomAdapter(myview.getContext(), -1, database.getAll());
listview.setAdapter(adapter);

Now, I want when the user deletes a database item the listview should refresh. Until now, I can successfully delete the item from the database, but it remains in the listview. In the ArrayAdapter class I call refresh() method from a new class same to adapter's parent class

    public void refresh(){
    ParentClass class_par = new ParentClass();
    class_par.refreshfromParent();
    }

And in the ParentClass I have a new method: refreshfromParent()

    public void refreshfromAlarm(){
    DatabaseHandler database = new DatabaseHandler(myview.getContext());
    listview.setAdapter(new CustomAdapter(myview.getContext(), -1, database.getAll())); // here I change listview adapter, and populate it with new database data, but I get NullPointerException
    }

So, how can I refresh listview items? Please, DO NOT mention notifyDataSetChanged(), it DOES NOT work.

yes, when you remove or change listitem data, just use above line. it make changes done by you — Divyesh Patel
– Divyesh Patel, Commented Dec 31, 2016 at 11:28
do not use any ArrayAdapter when your data model is Cursor related, use SimpleCursorAdapter instead — pskink
– pskink, Commented Dec 31, 2016 at 11:29
@pskink Yes, when I retrieve all my data from database I use cursor. So, should I use SimpleCursorAdapter ? If so, how will the super() be in public CustomAdapter? — Technologuy
– Technologuy, Commented Dec 31, 2016 at 11:33

Mubashar Javed · Accepted Answer · 2016-12-31 11:39:27Z

0

here you making en error

CustomAdapter adapter = new CustomAdapter(myview.getContext(), -1, database.getAll());
        listview.setAdapter(adapter);

    //so first you should make an arrayList and define it globally like
    // ArrayList <yourType>list = new ArrayList<>();

    //then initialize your adapter like this 

    list.addAll(databse.getAll());
    CustomAdapter adapter = new CustomAdapter(myview.getContext(), -1, list);
        listview.setAdapter(adapter);

    // now when you want to delete an item
    // delete it from your list like list.remove(location)
    // and also delete same item from your datebase
    // after that just call this
    notifyDataSetChanged();

answered Dec 31, 2016 at 11:39

Mubashar Javed

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2 Comments

Technologuy Over a year ago

It throws OutOfBoundsException. I finally decided to close and reload my fragment which contains my listview, so it has the same result.

Mubashar Javed Over a year ago

there should maybe some problem when you are deleting item from arraylist through specific location, that's way you are getting OutOfBoundsException error. reload fragment is not good approach

Technologuy · Accepted Answer · 2016-12-31 12:38:17Z

0

I realized that notifyDataSetChanged is a big trouble, so I decided to close and reload my fragment which contains my listview. Thus, the result looks the same with DataSetChanged and there is no difference in the users' eyes. I suggest everyone who reaches in this question do the same.

answered Dec 31, 2016 at 12:38

Technologuy

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