Question

The expected output is that data should be loaded once and then for every subsequent scroll. But instead, it is loading all the data in the listview at once.

public class ViewPage extends ListActivity{

ListView lv;
ListAdapter ld;
int size=3;

ArrayList<String> filename = new ArrayList<String>();
Cursor contactcursor;
ArrayAdapter<String> arr_ad;
int contact_column_index;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);

    setContentView(R.layout.mylist);




    String[] proj = { ContactsContract.Contacts.DISPLAY_NAME };
    contactcursor = managedQuery(ContactsContract.Contacts.CONTENT_URI, proj, null, null, null);
    contact_column_index = contactcursor.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME);
    lv = (ListView)findViewById(android.R.id.list);
    contactcursor.moveToFirst();
        for(int i=0;i<size;i++)
        {

            filename.add(contactcursor.getString(contact_column_index));
            if(!contactcursor.moveToNext())
                break;
        }

        arr_ad = new ArrayAdapter<String>(ViewPage.this, android.R.layout.simple_list_item_1, filename);
        setListAdapter(arr_ad);


        lv.setOnScrollListener(new EndlessScrollListener());
}

public class EndlessScrollListener implements OnScrollListener {

private int visibleThreshold = size;
private int currentPage = 0;
private int previousTotal = 0;
private boolean loading = true;

public EndlessScrollListener() 
{

}

public EndlessScrollListener(int visibleThreshold) 
{
    this.visibleThreshold = visibleThreshold;
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem,
        int visibleItemCount, int totalItemCount) {
    // TODO Auto-generated method stub



    /*Runnable action = new Runnable() {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        }
    };
    runOnUiThread(action);*/

    Toast.makeText(ViewPage.this, "In" , 1).show();
     if (loading) 
     {
         if (totalItemCount > previousTotal) 
         {
            loading = false;
            previousTotal = totalItemCount;
            currentPage++;
         }
     }
     if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) 
     { 


            for(int i=0;i<size;i++)
            {

                if(!contactcursor.moveToNext())
                    break;


                filename.add(contactcursor.getString(contact_column_index));

            }

            arr_ad.notifyDataSetChanged();

            loading = true;
            Toast.makeText(ViewPage.this,totalItemCount+" "+visibleItemCount+" "+firstVisibleItem+" "+visibleThreshold+" ", 1).show();
     }
}

@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
    // TODO Auto-generated method stub

}

}
}

The onscroll method in the endlessscrolllistener class runs and loads the complete data without even the scrolling being done. Thanx in advance.

Answer 1

onScroll gets called a lot, execute that logic while scrolling is pretty expensive in my opinion.

I achieved the goal adding a simple logic to my adapter, check this answer I gave a while ago.