Question

I have a problem that I can’t solve.

When I add items to a my database, I try to populate my listView and remove any item that equals " ", which are 3 blank spaces, from the listView, and NOT from the database just so that the users can’t see the empty rows. The method load() is called to do so. I keep getting a nullPointerException. It seems to find the item (I tested it with a System.out.println()) but when the remove method is called it crashes.

private void load() {       
    Cursor c=helper.getById(taskId);
    c.moveToFirst();                
    String[] temp = getArray(helper.getPart(c));

    ArrayAdapter<String> arrayAdapter =      
             new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, temp);
    lv.setAdapter(arrayAdapter); 

    int count = arrayAdapter.getCount();
    for (int i = 0; i < count; i++) {
        if (arrayAdapter.getItem(i).equals("   ")) {
            arrayAdapter.remove(arrayAdapter.getItem(i));
        }                    
    }

    arrayAdapter.notifyDataSetChanged();

    c.close();
}

Answer 1

Well it happens because the list is shrinking when you do a remove in your loop.

Let’s say the size is 10 (so index 0 – 9) in the beginning, then when you remove the first item which matches your condition, the real size its going back to 9, but in your loop you still have “i < 10” when you try to access the index i = 9 then you have a NullPointer Exception.

Try the following:

        for (int i = 0; i < arrayAdapter.getCount(); i++) {
             if(arrayAdapter.getItem(i).equals("   ")) {
                 arrayAdapter.remove(arrayAdapter.getItem(i));
             }                   
         }

Note that I replaced your count variable with getCount() inside the loop. When you do it like this you should never have the NullPointer Exception.