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android – Save ArrayList to SharedPreferences

Posted by: admin March 10, 2020 Leave a comment

Questions:

I have an ArrayList with custom objects. Each custom object contains a variety of strings and numbers. I need the array to stick around even if the user leaves the activity and then wants to come back at a later time, however I don’t need the array available after the application has been closed completely. I save a lot of other objects this way by using the SharedPreferences but I can’t figure out how to save my entire array this way. Is this possible? Maybe SharedPreferences isn’t the way to go about this? Is there a simpler method?

How to&Answers:

After API 11 the SharedPreferences Editor accept Sets. You could convert your List into a HashSet or something similar and store it like that. When your read it back, convert it into an ArrayList, sort it if needed and you’re good to go.

//Retrieve the values
Set<String> set = myScores.getStringSet("key", null);

//Set the values
Set<String> set = new HashSet<String>();
set.addAll(listOfExistingScores);
scoreEditor.putStringSet("key", set);
scoreEditor.commit();

You can also serialize your ArrayList and then save/read it to/from SharedPreferences. Below is the solution:

EDIT:
Ok, below is the solution to save ArrayList as serialized object to SharedPreferences and then read it from SharedPreferences.

Because API supports only storing and retrieving of strings to/from SharedPreferences (after API 11, its simpler), we have to serialize and de-serialize the ArrayList object which has the list of tasks into string.

In the addTask() method of the TaskManagerApplication class, we have to get the instance of the shared preference and then store the serialized ArrayList using the putString() method:

public void addTask(Task t) {
  if (null == currentTasks) {
    currentTasks = new ArrayList<task>();
  }
  currentTasks.add(t);

  // save the task list to preference
  SharedPreferences prefs = getSharedPreferences(SHARED_PREFS_FILE, Context.MODE_PRIVATE);
  Editor editor = prefs.edit();
  try {
    editor.putString(TASKS, ObjectSerializer.serialize(currentTasks));
  } catch (IOException e) {
    e.printStackTrace();
  }
  editor.commit();
}

Similarly we have to retrieve the list of tasks from the preference in the onCreate() method:

public void onCreate() {
  super.onCreate();
  if (null == currentTasks) {
    currentTasks = new ArrayList<task>();
  }

  // load tasks from preference
  SharedPreferences prefs = getSharedPreferences(SHARED_PREFS_FILE, Context.MODE_PRIVATE);

  try {
    currentTasks = (ArrayList<task>) ObjectSerializer.deserialize(prefs.getString(TASKS, ObjectSerializer.serialize(new ArrayList<task>())));
  } catch (IOException e) {
    e.printStackTrace();
  } catch (ClassNotFoundException e) {
    e.printStackTrace();
  }
}

You can get ObjectSerializer class from Apache Pig project ObjectSerializer.java

Answer:

Using this object –> TinyDB–Android-Shared-Preferences-Turbo its very simple.

TinyDB tinydb = new TinyDB(context);

to put

tinydb.putList("MyUsers", mUsersArray);

to get

tinydb.getList("MyUsers");

UPDATE

Some useful examples and troubleshooting might be found here: Android Shared Preference TinyDB putListObject frunction

Answer:

Saving Array in SharedPreferences:

public static boolean saveArray()
{
    SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this);
    SharedPreferences.Editor mEdit1 = sp.edit();
    /* sKey is an array */
    mEdit1.putInt("Status_size", sKey.size());  

    for(int i=0;i<sKey.size();i++)  
    {
        mEdit1.remove("Status_" + i);
        mEdit1.putString("Status_" + i, sKey.get(i));  
    }

    return mEdit1.commit();     
}

Loading Array Data from SharedPreferences

public static void loadArray(Context mContext)
{  
    SharedPreferences mSharedPreference1 =   PreferenceManager.getDefaultSharedPreferences(mContext);
    sKey.clear();
    int size = mSharedPreference1.getInt("Status_size", 0);  

    for(int i=0;i<size;i++) 
    {
     sKey.add(mSharedPreference1.getString("Status_" + i, null));
    }

}

Answer:

You can convert it to JSON String and store the string in the SharedPreferences.

Answer:

As @nirav said, best solution is store it in sharedPrefernces as a json text by using Gson utility class. Below sample code:

//Retrieve the values
Gson gson = new Gson();
String jsonText = Prefs.getString("key", null);
String[] text = gson.fromJson(jsonText, String[].class);  //EDIT: gso to gson


//Set the values
Gson gson = new Gson();
List<String> textList = new ArrayList<String>();
textList.addAll(data);
String jsonText = gson.toJson(textList);
prefsEditor.putString("key", jsonText);
prefsEditor.apply();

Answer:

Hey friends I got the solution of above problem without using Gson library. Here I post source code.

1.Variable declaration i.e

  SharedPreferences shared;
  ArrayList<String> arrPackage;

2.Variable initialization i.e

 shared = getSharedPreferences("App_settings", MODE_PRIVATE);
 // add values for your ArrayList any where...
 arrPackage = new ArrayList<>();

3.Store value to sharedPreference using packagesharedPreferences():

 private void packagesharedPreferences() {
   SharedPreferences.Editor editor = shared.edit();
   Set<String> set = new HashSet<String>();
   set.addAll(arrPackage);
   editor.putStringSet("DATE_LIST", set);
   editor.apply();
   Log.d("storesharedPreferences",""+set);
 }

4.Retrive value of sharedPreference using retriveSharedValue():

 private void retriveSharedValue() {
   Set<String> set = shared.getStringSet("DATE_LIST", null);
   arrPackage.addAll(set);
   Log.d("retrivesharedPreferences",""+set);
 }

I hope it will helpful for you…

Answer:

Android SharedPreferances allow you to save primitive types (Boolean, Float, Int, Long, String and StringSet which available since API11) in memory as an xml file.

The key idea of any solution would be to convert the data to one of those primitive types.

I personally love to convert the my list to json format and then save it as a String in a SharedPreferences value.

In order to use my solution you’ll have to add Google Gson lib.

In gradle just add the following dependency (please use google’s latest version):

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

Save data (where HttpParam is your object):

List<HttpParam> httpParamList = "**get your list**"
String httpParamJSONList = new Gson().toJson(httpParamList);

SharedPreferences prefs = getSharedPreferences(**"your_prefes_key"**, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = prefs.edit();
editor.putString(**"your_prefes_key"**, httpParamJSONList);

editor.apply();

Retrieve Data (where HttpParam is your object):

SharedPreferences prefs = getSharedPreferences(**"your_prefes_key"**, Context.MODE_PRIVATE);
String httpParamJSONList = prefs.getString(**"your_prefes_key"**, ""); 

List<HttpParam> httpParamList =  
new Gson().fromJson(httpParamJSONList, new TypeToken<List<HttpParam>>() {
            }.getType());

Answer:

You can also convert the arraylist into a String and save that in preference

private String convertToString(ArrayList<String> list) {

            StringBuilder sb = new StringBuilder();
            String delim = "";
            for (String s : list)
            {
                sb.append(delim);
                sb.append(s);;
                delim = ",";
            }
            return sb.toString();
        }

private ArrayList<String> convertToArray(String string) {

            ArrayList<String> list = new ArrayList<String>(Arrays.asList(string.split(",")));
            return list;
        }

You can save the Arraylist after converting it to string using convertToString method and retrieve the string and convert it to array using convertToArray

After API 11 you can save set directly to SharedPreferences though !!! 🙂

Answer:

This is your perfect solution.. try it,

public void saveArrayList(ArrayList<String> list, String key){
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(activity);
    SharedPreferences.Editor editor = prefs.edit();
    Gson gson = new Gson();
    String json = gson.toJson(list);
    editor.putString(key, json);
    editor.apply();     // This line is IMPORTANT !!!
}

public ArrayList<String> getArrayList(String key){
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(activity);
    Gson gson = new Gson();
    String json = prefs.getString(key, null);
    Type type = new TypeToken<ArrayList<String>>() {}.getType();
    return gson.fromJson(json, type);
}

Answer:

/**
 *     Save and get ArrayList in SharedPreference
 */

public void saveArrayList(ArrayList<String> list, String key){
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(activity);
    SharedPreferences.Editor editor = prefs.edit();
    Gson gson = new Gson();
    String json = gson.toJson(list);
    editor.putString(key, json);
    editor.apply();    

}

public ArrayList<String> getArrayList(String key){
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(activity);
    Gson gson = new Gson();
    String json = prefs.getString(key, null);
    Type type = new TypeToken<ArrayList<String>>() {}.getType();
    return gson.fromJson(json, type);
}

Answer:

I have read all answers above. That is all correct but i found a more easy solution as below:

  1. Saving String List in shared-preference>>

    public static void setSharedPreferenceStringList(Context pContext, String pKey, List<String> pData) {
    SharedPreferences.Editor editor = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).edit();
    editor.putInt(pKey + "size", pData.size());
    editor.commit();
    
    for (int i = 0; i < pData.size(); i++) {
        SharedPreferences.Editor editor1 = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).edit();
        editor1.putString(pKey + i, (pData.get(i)));
        editor1.commit();
    }
    

    }

  2. and for getting String List from Shared-preference>>

    public static List<String> getSharedPreferenceStringList(Context pContext, String pKey) {
    int size = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).getInt(pKey + "size", 0);
    List<String> list = new ArrayList<>();
    for (int i = 0; i < size; i++) {
        list.add(pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).getString(pKey + i, ""));
    }
    return list;
    }
    

Here Constants.APP_PREFS is the name of the file to open; can not contain path separators.

Answer:

Also with Kotlin:

fun SharedPreferences.Editor.putIntegerArrayList(key: String, list: ArrayList<Int>?): SharedPreferences.Editor {
    putString(key, list?.joinToString(",") ?: "")
    return this
}

fun SharedPreferences.getIntegerArrayList(key: String, defValue: ArrayList<Int>?): ArrayList<Int>? {
    val value = getString(key, null)
    if (value.isNullOrBlank())
        return defValue
    return ArrayList (value.split(",").map { it.toInt() }) 
}

Answer:

You could refer the serializeKey() and deserializeKey() functions from FacebookSDK’s SharedPreferencesTokenCache class. It converts the supportedType into the JSON object and store the JSON string into SharedPreferences. You could download SDK from here

Answer:

best way is that convert to JSOn string using GSON and save this string to SharedPreference.
I also use this way to cache responses.

Answer:

For String, int, boolean, the best choice would be sharedPreferences.

If you want to store ArrayList or any complex data. The best choice would be Paper library.

Add dependency

Initialize Paper

Should be initialized once in Application.onCreate():

Save

Loading Data

Use default values if object doesn’t exist in the storage.

Here you go.

https://github.com/pilgr/Paper

Answer:

The best way i have been able to find is a make a 2D Array of keys and put the custom items of the array in the 2-D array of keys and then retrieve it through the 2D arra on startup.
I did not like the idea of using string set because most of the android users are still on Gingerbread and using string set requires honeycomb.

Sample Code:
here ditor is the shared pref editor and rowitem is my custom object.

Answer:

following code is the accepted answer, with a few more lines for new folks (me), eg. shows how to convert the set type object back to arrayList, and additional guidance on what goes before ‘.putStringSet’ and ‘.getStringSet’. (thank you evilone)

Answer:

don’t forget to implement Serializable:

https://stackoverflow.com/a/7635154/4639974

Answer:

You can use serialization or Gson library to convert list to string and vice versa and then save string in preferences.

Using google’s Gson library:

Using Java serialization:

Answer:

You can save String and custom array list using Gson library.

=>First you need to create function to save array list to SharedPreferences.

=> You need to create function to get array list from SharedPreferences.

=> How to call save and retrieve array list function.

=> Don’t forgot to add gson library in you app level build.gradle.

implementation ‘com.google.code.gson:gson:2.8.2’

Answer:

This method is used to store/save array list:-

This method is used to retrieve array list:-

Answer:

You can convert it to a Map Object to store it, then change the values back to an ArrayList when you retrieve the SharedPreferences.

Answer:

Why don’t you stick your arraylist on an Application class? It only get’s destroyed when the app is really killed, so, it will stick around for as long as the app is available.

Answer:

Answer:

Use this custom class:

How to use:

Answer:

this should work:

them, to catch it just:

it works for me.

Answer:

My utils class for save list to SharedPreferences

Using

.
Full code of my utils // check using example in Activity code

Answer:

I used the same manner of saving and retrieving a String but here with arrayList I’ve used HashSet as a mediator

To save arrayList to SharedPreferences we use HashSet:

1- we create SharedPreferences variable (in place where the change happens to the array)

2 – we convert the arrayList to HashSet

3 – then we put the stringSet and apply

4 – you getStringSet within HashSet and recreate ArrayList to set the HashSet.

Answer:

Answer:

All of the above answers are correct. 🙂 I myself used one of these for my situation. However when I read the question I found that the OP is actually talking about a different scenario than the title of this post, if I didn’t get it wrong.

“I need the array to stick around even if the user leaves the activity and then wants to come back at a later time”

He actually wants the data to be stored till the app is open, irrespective of user changing screens within the application.

“however I don’t need the array available after the application has been closed completely”

But once the application is closed data should not be preserved.Hence I feel using SharedPreferences is not the optimal way for this.

What one can do for this requirement is create a class which extends Application class.

Using the setter and getter the ArrayList can be accessed from anywhere withing the Application. And the best part is once the app is closed, we do not have to worry about the data being stored. 🙂