Storing ArrayList in SharedPreferences messes up the element order

Question

I am using SharedPreferences to save and load my ArrayList like this: (save)

        SharedPreferences loadGlobalVariables = getSharedPreferences(APP_NAME, 0);
        Categories = new ArrayList<String>(loadGlobalVariables.getStringSet("Categories", new HashSet<String>()));

(Load) And this (they both work fine, both saves and loads correctly)

 SharedPreferences saveGlobalVariables = getSharedPreferences(APP_NAME, 0);
    SharedPreferences.Editor editor = saveGlobalVariables.edit();
    editor.putStringSet("Categories", new HashSet<String>(Categories));
    editor.commit();

But the retrieved ArrayList has different element order than before. I know this because I put this ArrayList into a Dialog as a list (this list is refreshed every time I open it.), by Category.toArray(temArray), and the list is no longer alphabetical.

Before, this ArrayList alphabetically sorted String elements inside it. When I retrieve it back from the SharedPreferences, it is no longer alphabetically sorted.

Thank you for you help, in advance.

Hashes and sets are unordered. – Dave Newton Jan 23 '13 at 12:25 — Dave Newton, Jan 23 '13 at 12:25

score 9 · Accepted Answer · edited Jun 23 '14 at 02:11

9

I had overcome this situation with a trick.

In SharedPreferences first store the size of the ArrayList.
In a for loop store the elements of the arraylist into the SharedPreferences File .

Now here is the trick while storing as key-value pair keep key "ArraylistName" + position of element

While retrieving:

First retrieve the size of the arrayList
for (i = 0 ; i < sizeOfList ; i++) { fetch element with key value "ArrayListName" + i }

edited Jun 23 '14 at 02:11

Stephen Ostermiller

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answered Jan 23 '13 at 12:35

pvn

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Thats a great idea! I was thinking something like that too! I will try this and mark this as an answer if it work – coolcool1994 Jan 24 '13 at 03:19
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Perfect. Thank you! (I thumbed up too:)) – coolcool1994 Jan 24 '13 at 05:45

score 1 · Answer 2 · edited May 23 '17 at 12:24

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In Java Set doesn't maintain the order of its elements. Unfortunately SharedPreferences.Editor doesn't provide a way to store a list so you should probably serialize the list into string and use putString().

See Store a List or Set in SharedPreferences.

edited May 23 '17 at 12:24

Community

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answered Jan 23 '13 at 12:25

pingw33n

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Storing ArrayList in SharedPreferences messes up the element order

2 Answers2