How to save HashMap to Shared Preferences?

Question

How can I save a HashMap Object into Shared Preferences in Android?

Answer 1

I use Gson to convert HashMap to String and then save it to SharedPrefs

private void hashmaptest() {     //create test hashmap     HashMap<String, String> testHashMap = new HashMap<String, String>();     testHashMap.put("key1", "value1");     testHashMap.put("key2", "value2");      //convert to string using gson     Gson gson = new Gson();     String hashMapString = gson.toJson(testHashMap);      //save in shared prefs     SharedPreferences prefs = getSharedPreferences("test", MODE_PRIVATE);     prefs.edit().putString("hashString", hashMapString).apply();      //get from shared prefs     String storedHashMapString = prefs.getString("hashString", "oopsDintWork");     java.lang.reflect.Type type = new TypeToken<HashMap<String, String>>(){}.getType();     HashMap<String, String> testHashMap2 = gson.fromJson(storedHashMapString, type);      //use values     String toastString = testHashMap2.get("key1") + " | " + testHashMap2.get("key2");     Toast.makeText(this, toastString, Toast.LENGTH_LONG).show(); } 

Answer 2

I would not recommend writing complex objects into SharedPreference. Instead I would use ObjectOutputStream to write it to the internal memory.

File file = new File(getDir("data", MODE_PRIVATE), "map");     ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(file)); outputStream.writeObject(map); outputStream.flush(); outputStream.close();