How to Save Hashmap to Shared Preferences

How to save HashMap to Shared Preferences?

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();

Saving hash map into SharedPreferences

Function to Insert HashMap into SharedPreference

private void insertToSP(HashMap<String, List<String>> jsonMap) {
  String jsonString = new Gson().toJson(jsonMap);
  SharedPreferences sharedPreferences = getSharedPreferences("HashMap", MODE_PRIVATE);
  SharedPreferences.Editor editor = sharedPreferences.edit();
  editor.putString("map", jsonString);
  editor.apply();
}

Function to read hashMap from SharedPreference

private HashMap<String, List<String>> readFromSP(){
   SharedPreferences sharedPreferences = getSharedPreferences("HashMap", MODE_PRIVATE);
   String defValue = new Gson().toJson(new HashMap<String, List<String>>());
   String json=sharedPreferences.getString("map",defValue);
   TypeToken<HashMap<String,List<String>>> token = new TypeToken<HashMap<String,List<String>>>() {};
   HashMap<String,List<String>> retrievedMap=new Gson().fromJson(json,token.getType());
   return retrievedMap;
}

Add this dependancy in gradle

implementation 'com.google.code.gson:gson:2.6.2'

Save hashmap in SharedPreferences

Gson is not recognizing the anonymous class that results from doing it that way.

Try initializing the map without using the {{}} construct.
e.g.

Map<String, String> userMap = new HashMap<String , String>();

for(int i = 0; i < userList.size(); i++ ) {
    String id= userList.get(i).getId();
    String name = userList.get(i).getName();
    put(id, name);
}

Gson gson = new Gson();
String jsonString = gson.toJson(userMap);
SessionManager sessionManager=new SessionManager(LoginActivity.this);
sessionManager.saveMap(jsonString); 

To convert this json back to a Map<String, String> you can use TypeToken as suggested here.

Gson gson = new Gson();
Type type = new TypeToken<Map<String, String>>() {}.getType();
Map<String, String> nameEmployeeMap = gson.fromJson(jsonString, type);

Android: Save map to SharedPreferences?

When saving more complex types in Android, I would suggest using gson. Gson is Google's JSON parsing library, and even if you're not using JSON, you can convert your Objects into a JSON String, and store that easily.

For example, you can convert your list of Objects into a String like this.

val list : List<MyObject>  // ... add items to your list

// Convert to JSON

val string = gson.toJson(list)

// Store it into Shared Preferences
preferences.putString("list", string).apply()

And then you can easily get it back into a list like this.

// Fetch the JSON 

val string = preferences.getString("list", "")

// Convert it back into a List

val list: List<MyObject> = gson.fromJson(string, object : TypeToken<List<MyObject>>() {}.type)

How to save hashmap to shared preference?

Try this to save objects in SharedPreferences.

you need to add Gson library to your project.

public void putMyObject(String key , Object obj) {

        //AnyVehicleModel mvehicle  =new AnyVehicleModel();
        SharedPreferences.Editor editor = preferences.edit();
        Gson gson = new Gson();
        String json = gson.toJson(obj);
        editor.putString(key,json);
        editor.apply();
    }




    public MyObject getMyObject(String key) {

        Gson gson = new Gson();
        String json = preferences.getString(key,"");
        MyObject obj = gson.fromJson(json, MyObject.class);
        if (obj== null){return new MyObject ();}
        return obj;

    }

how to store ArrayList HashMap String, String data into sharedpreferences?

Convert your array or object to JSON and store into shared pref

for storing:

SharedPreferences db=PreferenceManager.getDefaultSharedPreferences(context);

Editor collection = db.edit();
Gson gson = new Gson();
String arrayList1 = gson.toJson(arrayList);

collection.putString(key, arrayList1);
collection.commit();

for retrieving

SharedPreferences db=PreferenceManager.getDefaultSharedPreferences(context);

Gson gson = new Gson();
String arrayListString = db.getString(key, null);  
Type type = new TypeToken<ArrayList<ArrayObject>>() {}.getType();
ArrayList<ArrayObject> arrayList = gson.fromJson(arrayListString, type);

How can I store a HashMap Integer, String in android using shared preferences?

Hey I found a way in the end :)

I just changed the HashMap I had to format and then did the following to save the contents:

SharedPreferences.Editor editor = getSharedPreferences(PREFS_NAME, 0).edit();
for( Entry entry : backUpCurency_values.entrySet() ) 
editor.putString( entry.getKey(), entry.getValue() );
editor.commit();

and the following to retrieve the HashpMap:

SharedPreferences prefs = getSharedPreferences(PREFS_NAME, 0);
for( Entry entry : prefs.getAll().entrySet() )
   backUpCurency_values.put( entry.getKey(), entry.getValue().toString() );

Retrieve hashmap data SharedPreferences

There is no support for HashMap in SharedPreferences. So, you can't save the HashMap by converting it to a string directly, but you can convert it to JSON string. You can use google-gson in this case. Something like this:

First, include the dependency:

compile 'com.google.code.gson:gson:2.8.2'

Saving from HashMap object to preference:

Editor prefsEditor = mPrefs.edit();
Gson gson = new Gson();
String json = gson.toJson(map);
prefsEditor.putString("YourHashMap", json);
prefsEditor.commit();

Get HashMap object from preference:

Gson gson = new Gson();
String json = mPrefs.getString("YourHashMap", "");
HashMap map = gson.fromJson(json, HashMap.class);

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