Clone new objects to pass to ArrayList?

Question

I'm building an android app and I was trying to add objects to an ArrayList. I thought this would create a copy of the object in ArrayList and then I could reuse the object. I've realized this isn't the case and that ArryList was actually referencing the original object.

I'm not really sure how I'd use a loop to create new objects in the onCreate function so do I somehow need to clone the object and pass it to the ArrayList?

Anyway here's my code:

 public class Main extends Activity {
  private Item myItem = new Item();

  btnSave.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            alItems.add(myItem);
            arrayAdapter.notifyDataSetChanged();

score 3 · Accepted Answer · edited May 23 '17 at 12:12

3

You can create a copy constructor in your Item class, and use it to create a copy of your object.

public class Item {
    private int field1;
    public Item() { }

    public Item(Item item) {
       this.field1 = item.field1;
    }
}

And add your object to list using: -

alItems.add(new Item(myItem));

edited May 23 '17 at 12:12

Community

1
1

answered Nov 05 '12 at 21:13

Rohit Jain

209,639
45
409
525

Brilliant didn't know about copy constructors and it worked a treat! – KingFu Nov 05 '12 at 21:52

score 2 · Answer 2 · answered Nov 05 '12 at 21:17

2

Make your Item implement Clonable then

public void onClick(View v) {
        alItems.add(myItem.clone());
        arrayAdapter.notifyDataSetChanged();

answered Nov 05 '12 at 21:17

Roman C

49,761
33
66
176

1

A copy constructor is a better way to go than using `clone` method. Take a look at `Effective Java - Item # 11` – Rohit Jain Nov 05 '12 at 21:20
@RohitJain I'v used copy constructor in my environment but migrated to cloning and it had greatly simplified the implementation. – Roman C Nov 05 '12 at 21:25

Clone new objects to pass to ArrayList?

2 Answers2