CODEWITHSUNDEEP
javaandroidjsondictionarysharedpreferences
Daniele Di Fratta
Daniele Di Fratta

Reputation: 3

Save hash map Shared Preferences

I'm triyng to save an HashMap into SharedPreferences but i get this error when i load the map:

java.lang.ClassCastException: org.json.JSONArray cannot be cast to java.util.List

I adapted the code i found online but i don't understand why i get this error.

Here is the code:

public static Map<String, List<Integer>> loadMap() {
    Map<String,List<Integer>> outputMap = new HashMap<>();
    SharedPreferences pSharedPref =             MainActivity.getContextofApplication().getSharedPreferences(NETWORK_PREF, Activity.MODE_PRIVATE);
    try{
        if (pSharedPref != null){
            String jsonString = pSharedPref.getString(RSSI_MAP, (new JSONObject()).toString());
            JSONObject jsonObject = new JSONObject(jsonString);
            Iterator<String> keysItr = jsonObject.keys();
            while(keysItr.hasNext()) {
                String key = keysItr.next();
                List<Integer> value = (List<Integer>) jsonObject.get(key);
                outputMap.put(key, value);
            }
        }
    }catch(Exception e){
        e.printStackTrace();
    }
    return outputMap;
}

public void saveRSSI() {
    SharedPreferences pref = MainActivity.getContextofApplication().getSharedPreferences(NETWORK_PREF,Activity.MODE_PRIVATE);
    JSONObject jsonObject = new JSONObject(this.RSSImap);
    String jsonString = jsonObject.toString();
    SharedPreferences.Editor editor = pref.edit();
    editor.putString(RSSI_MAP, jsonString);
    editor.commit();
}

Upvotes: 0

Views: 250

Answers (1)

user1626594
user1626594

Reputation:

The Exception is telling you what is the problem, you need to get the list from JSON. Try replacing your while cycle with this one:

            while(keysItr.hasNext()) {
                String key = keysItr.next();
                JSONArray jlist = jsonObject.getJSONArray(key);
                List<Integer> list = new ArrayList<>();
                for(int i=0; i < jlist.length(); i++){
                    list.add(jlist.getInt(i));
                }
                outputMap.put(key, list);
            }

Upvotes: 2

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