How to save custom ArrayList on Android screen rotate?

You do not need to create a new class to pass an ArrayList of your custom objects. You should simply implement the Parcelable class for your object and use Bundle#putParcelableArrayList() in onSaveInstanceState() and onRestoreInstanceState(). This method will store an ArrayList of Parcelables by itself.

Because the subject of Parcelables (and Serializables and Bundles) sometimes makes my head hurt, here is a basic example of an ArrayList containing custom Parcelable objects stored in a Bundle. (This is cut & paste runnable, no layout necessary.)

Implementing Parcelable

public class MyObject implements Parcelable {    String color;    String number;    public MyObject(String number, String color) {        this.color = color;        this.number = number;    }    private MyObject(Parcel in) {        color = in.readString();        number = in.readString();    }    public int describeContents() {        return 0;    }    @Override    public String toString() {        return number + ": " + color;    }    public void writeToParcel(Parcel out, int flags) {        out.writeString(color);        out.writeString(number);    }    public static final Parcelable.Creator<MyObject> CREATOR = new Parcelable.Creator<MyObject>() {        public MyObject createFromParcel(Parcel in) {            return new MyObject(in);        }        public MyObject[] newArray(int size) {            return new MyObject[size];        }    };}

Save / Restore States

public class Example extends ListActivity {    ArrayList<MyObject> list;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        if(savedInstanceState == null || !savedInstanceState.containsKey("key")) {            String[] colors = {"black", "red", "orange", "cyan", "green", "yellow", "blue", "purple", "magenta", "white"};            String[] numbers = {"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten"};            list = new ArrayList<MyObject>();            for(int i = 0; i < numbers.length; i++)                 list.add(new MyObject(numbers[i], colors[i]));        }        else {            list = savedInstanceState.getParcelableArrayList("key");        }        setListAdapter(new ArrayAdapter<MyObject>(this, android.R.layout.simple_list_item_1, list));    }    @Override    protected void onSaveInstanceState(Bundle outState) {        outState.putParcelableArrayList("key", list);        super.onSaveInstanceState(outState);    }}

You can use onRetainNonConfigurationInstance(). It allows you to save any object before an configuration change, and restore it after with getLastNonConfigurationInstanceState().

Inside the activity:

    @Override    public Object onRetainNonConfigurationInstance() {        return myArrayList;    }

Inside onCreate():

    try{        ArrayList myArrayList = (ArrayList)getLastNonConfigurationInstance();    } catch(NullPointerException e) {}

Handling Runtime Changes: http://developer.android.com/guide/topics/resources/runtime-changes.htmlDocumentation: http://developer.android.com/reference/android/app/Activity.html#onRetainNonConfigurationInstance%28%29

public void onSaveInstanceState(Bundle outState) {    super.onSaveInstanceState(outState);    ArrayList<Integer> id=new ArrayList<>();    ArrayList<String> title=new ArrayList<>();    for(int i=0;i<arr.size();i++){        id.add(arr.get(i).id);        title.add(arr.get(i).title);    }    outState.putIntegerArrayList("id",id);    outState.putStringArrayList("title",title);}