how to store and retrieve (key,value) kind of data using saved preferences android

Question

I have a hash map table as below,

HashMap backUpCurency_values = new HashMap();

and i want to

Answer 1

There are a few different ways to approach this. With nothing more to go on than the info that you want to store a HashMap to SharedPreferences, I can only make assumptions.

First thing I'd ask is whether you will be storing other things in the SharedPreferences as well- I'll assume you will.

Here is how I would approach it:

    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
    SharedPreferences.Editor editor = prefs.edit();
    editor.putString("backUpCurency", stringify(backUpCurency_values));
    editor.commit();

You may want to see what stringify does:

   // turns a HashMap into "key=value|key=value|key=value"
   private String stringify(HashMap map) {
       StringBuilder sb = new StringBuilder();
       for (String key : map.keySet()) {
           sb.append(key).append("=").append(map.get(key)).append("|");
       }
       return sb.substring(0, sb.length() - 1); // this may be -2, but write a unit test
   }

Then you can just parse that string with known structure upon reading the shared preferences later.

   private HashMap restoreIt() {
      SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
      String backup = settings.getString("backUpCurency", "");
      HashMap map = new HashMap();
      for (String pairs : backup.split("|")) {
         String[] indiv = pairs.split("=");
         map.put(indiv[0], indiv[1]);
      }
      return map;
   }