Android: Save a ArrayList in SharedPreference

Question

I hope anyone of you can help me.

I make a game like 4Pics1Word.

My problem is I want to load the Level Randomly, so I use a solution which I get from this Question: Android: Check Array for a number Random

public SharedPreference() {
    super();        
}

// This four methods are used for maintaining favorites.
public static void savePreferences(Context context) {
    SharedPreferences settings;
    Editor editor;
    settings = context.getSharedPreferences(PREFS_NAME,
            Context.MODE_PRIVATE);
    editor = settings.edit();

    System.out.println("FirstTime is " + firstTime);            
    editor.putInt(Coins, FlagsOfNations.getCoins());
    editor.putInt(CurrentQuestion, FlagsOfNations.getCurrentQuestion());
    editor.putInt(CurrentImage, FlagsOfNations.getCurrentImage());
    editor.putBoolean("FirstTimeCreate", firstTime);
        int a = 0;
    for (int i = 0; i < 10; i++); { 
        editor.putInt("list_"+ a, list.get(a));
        a++;
        System.out.println("Es wurde gespeichert: " + list.get(a));
    }       
    editor.commit();
}

public static void loadPreferences(Context context) {
    SharedPreferences settings;

    settings = context.getSharedPreferences(PREFS_NAME,
            Context.MODE_PRIVATE);

    FlagsOfNations.setCoins(settings.getInt(Coins, 400));
    FlagsOfNations.setCurrentQuestion(settings.getInt(CurrentQuestion, -1));
    FlagsOfNations.setCurrentQuestion(settings.getInt(CurrentImage, -1));
    AlertDialogFragment1.setAktuellerButton(settings.getInt("test32", 0));
    firstTime = settings.getBoolean("FirstTimeCreate", true);

    if (firstTime == true) {
        // list in loadpreference und dann in flagsofnation bei start nur load nicht save
        for (int i = 0; i < 10; i++) {
            list.add(i);                
        }
        Collections.shuffle(list);

        // output the generated list
        for (int i = 0; i < 10; i++) {
            System.out.println("UsedImage: " + list.get(i));
        }


        firstTime = false;
        }
    int size = 10;
    size = settings.getInt("ListSize", 10);
    System.out.println("Size of List: " + size);
    int a = 0;

    for (int i = 0; i < size; i++); {
        list.set(a, settings.getInt("list_"+ a, 0));
        System.out.println("Es wurde gespeichert: " + list.get(a));
        a++;
    }
    System.out.println("List  asd save: " + list.get(0));
    System.out.println("List  asd save: " + list.get(1));
    System.out.println("List  asd save: " + list.get(2));
    System.out.println("List  asd save: " + list.get(3));
    System.out.println("List  asd save: " + list.get(4));
    System.out.println("List  asd save: " + list.get(5));
    System.out.println("List  asd save: " + list.get(6));
    System.out.println("List  asd save: " + list.get(7));
    System.out.println("List  asd save: " + list.get(8));
    System.out.println("List  asd save: " + list.get(9));
}

If I try it, it work if I close the Game with the Backbutton or the homebutton and start it again it work. But If I click on the (Sorry I don´t know the english word for this button where I can switch to other open apps) and then close the game on the Menu where I can see all open apps and then restart the application I got this error:

03-19 21:57:11.071: E/AndroidRuntime(2989): FATAL EXCEPTION: main
03-19 21:57:11.071: E/AndroidRuntime(2989): Process: com.developer.flagsofnations, PID: 2989
03-19 21:57:11.071: E/AndroidRuntime(2989): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.developer.flagsofnations/com.developer.flagsofnations.FlagsOfNations}: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
03-19 21:57:11.071: E/AndroidRuntime(2989):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2596)
03-19 21:57:11.071: E/AndroidRuntime(2989):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2653)
03-19 21:57:11.071: E/AndroidRuntime(2989):     at android.app.ActivityThread.access$800(ActivityThread.java:156)
03-19 21:57:11.071: E/AndroidRuntime(2989):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1355)

I hope you can help me

I got it work with the following code.

public static void savePreferences(Context context) {
    SharedPreferences settings;
    Editor editor;
    settings = context.getSharedPreferences(PREFS_NAME,
            Context.MODE_PRIVATE);
    editor = settings.edit();

    System.out.println("FirstTime is " + firstTime);

    editor.putInt(Coins, FlagsOfNations.getCoins());
    editor.putInt(CurrentQuestion, FlagsOfNations.getCurrentQuestion());
    editor.putInt(CurrentImage, FlagsOfNations.getCurrentImage());
    editor.putBoolean("FirstTimeCreate", firstTime);

    editor.putString("GsonGson", Test);
    editor.commit();
}

public static void loadPreferences(Context context) {
    SharedPreferences settings;

    settings = context.getSharedPreferences(PREFS_NAME,
            Context.MODE_PRIVATE);

    FlagsOfNations.setCoins(settings.getInt(Coins, 400));
    FlagsOfNations.setCurrentQuestion(settings.getInt(CurrentQuestion, -1));
    FlagsOfNations.setCurrentQuestion(settings.getInt(CurrentImage, -1));
    AlertDialogFragment1.setAktuellerButton(settings.getInt("test32", 0));
    firstTime = settings.getBoolean("FirstTimeCreate", true);

    // list in loadpreference und dann in flagsofnation bei start nur
    // load nicht save
    for (int i = 0; i < 10; i++) {

        listTest.add(i);

    }
    Collections.shuffle(listTest);

    // output the generated list
    for (int i = 0; i < 10; i++) {
        System.out.println("UsedImage: " + listTest.get(i));
    }

    Gson gson = new Gson();
    String jsonList = gson.toJson(listTest);
    Log.d("TAG", "jsonList = " + jsonList);

    Test = settings.getString("GsonGson", jsonList);

    Type type = new TypeToken<ArrayList<Integer>>() {
    }.getType();
    list = gson.fromJson(Test, type);

    Log.d("TAG", "list = " + list);

}

I call this class so in OnCreate in MainActivity:

    SharedPreference.loadPreferences(getApplicationContext());

And this in MainActivity to save:

    @Override
protected void onStop() {
    super.onStop();

    SharedPreference.savePreferences(getApplicationContext());
}

@Override
public void onDestroy() {
    super.onDestroy();
    if (mHelper != null)
        mHelper.dispose();
    mHelper = null;

    SharedPreference.savePreferences(getApplicationContext());
}

I have only one question is it right to call the save Method in onDestroy and OnStop?

possible duplicate of [Save ArrayList to SharedPreferences](http://stackoverflow.com/questions/7057845/save-arraylist-to-sharedpreferences) — Jared Burrows, Mar 19 '15 at 21:10

score 0 · Answer 1 · answered Mar 19 '15 at 21:12

The issue with your code might be that you are calling

list.set(a, settings.getInt("list_"+ a, 0));

Instead, just do list.add() because you are adding the items in order anyway.

Also, ff this isn't performance critical, you could serialize your array to a string using google's Gson lib. Then, rather than looping, you would just convert the array to a string and save it in shared prefs, and deserialize the array on start. That might simplify your code a little.

Android: Save a ArrayList in SharedPreference

1 Answers1