How can I store Arraylists in class?

Question

I have a class data, where I store my user data.

public class deck {
    public static ArrayList deck = new ArrayList();
    public static ArrayList cardchosen = new ArrayList();
    public static ArrayList deck1Image = new ArrayList();
    public static ArrayList deck2Image = new ArrayList();
}

How can I save the state of those Arrays in onSaveInstanceState? Do I have to use something different?

What is the type of ArrayList() for deck, cardchosen, deck1Image, deck2Image? — Kristy Welsh
– Kristy Welsh, Commented Feb 11, 2021 at 15:27
I already tried with outstate.getIntegerArraylist but it gets red underline... — gi pi
– gi pi, Commented Feb 11, 2021 at 15:28

Kamil Jeglikowski · Accepted Answer · 2021-02-11 15:58:27Z

2

The easier would be to implement Serializable interface in your data class

public class Deck implements Serializable {

    public static ArrayList deck = new ArrayList();
    public static ArrayList cardchosen = new ArrayList();
    public static ArrayList deck1Image = new ArrayList();
    public static ArrayList deck2Image = new ArrayList();
}

and then set bundle like that in onSaveInstanceState

kotlin

    override fun onSaveInstanceState(outState: Bundle, outPersistentState: PersistableBundle) {
        val deck = Deck()
        outState.putSerializable("mydeck", deck)
        super.onSaveInstanceState(outState, outPersistentState)
    }

Java

@Override
public void onSaveInstanceState(Bundle outState) {
   outState.putSerializable("mydeck", deck);
   super.onSaveInstanceState(outState);
}

edited Feb 11, 2021 at 15:58

answered Feb 11, 2021 at 15:28

Kamil Jeglikowski

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5 Comments

gi pi Over a year ago

Where do I put the onSaveInstanceState? In MainActivity? Because class deck doesn't have OnCreate so there's nothing to overrider...

Kamil Jeglikowski Over a year ago

Yes, In your activity

gi pi Over a year ago

Unfortunately need in java

gi pi Over a year ago

Thanks! But how can I restore that data after reopening the app? Also in MainActivity? And if so, what's the best way to get my saved data back in my deck class?

Kamil Jeglikowski Over a year ago

@gipi Please check this stackoverflow.com/a/24075364/11538132

Kristy Welsh · Accepted Answer · 2021-02-11 15:35:26Z

1

You need to implicitly declare the type of ArrayList:

public class deck {
    public static ArrayList deck = new ArrayList<Integer>();
    public static ArrayList cardchosen = new ArrayList<Integer>();
    public static ArrayList deck1Image = new ArrayList<Integer>();
    public static ArrayList deck2Image = new ArrayList<Integer>();
}

The compiler has no idea otherwise when you're trying to do:

ArrayList myArrayList = outstate.getIntegerArrayList("My Key")

answered Feb 11, 2021 at 15:35

Kristy Welsh

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