Android saving an ArrayList onPause and onSaveInstanceState

Question

I have an ArrayList filled with some custom POJO's that I'd like to persist when the user switches screen orientation (onSaveInstanceState) and when e.g. the user hits the back button (onPause).

As far as I know, the SharedPreferences can only hold primitive data types and bundles can not hold references to generic ArrayLists.

Any tips on how to tackle this?

Regards,

Marcus

Hitting back will not only pause, but also destroy your `Activity`. With that in mind, you'll need to write the data to some sort of file if you want it to survive. Were you instead just referring to instances where the user might be interrupted in their use of your app? — NasaGeek, Sep 25 '14 at 09:48
Answer = http://stackoverflow.com/questions/7145606/how-android-sharedpreferences-save-store-object + http://stackoverflow.com/questions/7361627/how-can-write-code-to-make-sharedpreferences-for-array-in-android/7361989#7361989 — Piyush Kukadiya, Sep 25 '14 at 10:12

score 1 · Answer 1 · answered Sep 25 '14 at 09:49

i don't know this is correct method or not but i handle this like this this always success while your app lost all cache data itself then also u can get back serializable object->

for generic ArrayLists always use serializable

just look at once http://developer.android.com/reference/java/io/Serializable.html

score 1 · Accepted Answer · answered Sep 25 '14 at 12:57

1

1- create a class and put everything you want to store for example arraylist of your POJO and make that class implement Serializable interface.

class MyBundle  implements Serializable {

   ArrayList<POJO> mPOJO;


   MyBundle( ArrayList<POJO> pojo){

    mPOJO= pojo;


   }

}

2- write it to file:

 ObjectOutputStream oos = null;
 FileOutputStream fout = null;
 try{
        FileOutputStream fout = new FileOutputStream("Your file path");
        ObjectOutputStream oos = new ObjectOutputStream(fout);
        oos.writeObject(mb); // mb is an instance of MyBundle
 } catch (Exception ex) {
        e.printStackTrace();
 }finally {
   if(oos  != null){
     oos.close();
   } 
 }

and to get back everything:

 ObjectInputStream objectinputstream = null;
 try {
        streamIn = new FileInputStream("Your file address");
        objectinputstream = new ObjectInputStream(streamIn);
        MyBundle mb = (MyBundle) objectinputstream.readObject();

   } catch (Exception e) {
        e.printStackTrace();
   }finally {
     if(objectinputstream != null){
        objectinputstream .close();
     } 
   }

answered Sep 25 '14 at 12:57

mmlooloo

18,937
5
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Is there really no other way than creating a file to store one simple array list? – Marcus Sep 25 '14 at 14:50
for `onSaveInstanceState` you can use `ParcelableArray` but for `user hits the back button` you must use `file` or `database`. – mmlooloo Sep 25 '14 at 15:10
I would rather use a database than writing to a file – Marcus Sep 25 '14 at 15:20
I tried the serialize approach. Where should I serialize my array? OnDestroy? – Marcus Sep 25 '14 at 17:53
if you want to handle `onSaveInstanceState` you should do it at `onStop`. – mmlooloo Sep 25 '14 at 18:00
So if I understand that right: serialize at onSaveInstanceState, de-serialize at onStart? – Marcus Sep 25 '14 at 18:12
Will this cover events such as user press home or navigate to another activity? – Marcus Sep 25 '14 at 18:13
serialize at `onStop` and `de-serialize` at `onCreate`. Yes. – mmlooloo Sep 25 '14 at 18:16
I'll try it out tomorrow, if it works I'll set this as the answer. Thanks for your help . – Marcus Sep 25 '14 at 18:26

score 0 · Answer 3 · answered Sep 25 '14 at 09:49

0

Try converting the List to Json using Gson or Jackson. Store the string in the Shared preference. some thing like below code

String listString = gsonSD.toJson(list<object> instance);
SharedPreferences storeDataPref = getContext().getSharedPreferences("list_store_pref", Context.MODE_PRIVATE);
Editor storeDataEditor = storeDataPref.edit();
storeDataEditor.putString("liststringdata", listString).apply();

answered Sep 25 '14 at 09:49

Harsha Vardhan

3,324
2
17
22

Ill try it out, where can I download it? (a version that isnt deprecated) – Marcus Sep 25 '14 at 10:19
sorry, I am not able to get...where can i download it? – Harsha Vardhan Sep 25 '14 at 11:25

Android saving an ArrayList onPause and onSaveInstanceState

3 Answers3