Save ArrayList to SharedPreferences

Question

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

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this should work   public void setSections  Context c   List lt Section gt  sectionList       this sectionList   sectionList       Type sectionListType   new TypeToken lt ArrayList lt Section gt  gt      getType        String sectionListString   new Gson   toJson sectionList sectionListType        SharedPreferences Editor editor   getSharedPreferences c  edit   putString PREFS KEY SECTIONS  sectionListString       editor apply        them  to catch it just   public List lt Section gt  getSections Context c        if this sectionList    null           String sSections   getSharedPreferences c  getString PREFS KEY SECTIONS  null            if sSections    null               return new ArrayList lt  gt                        Type sectionListType   new TypeToken lt ArrayList lt Section gt  gt      getType            try                this sectionList   new Gson   fromJson sSections  sectionListType                if this sectionList    null                   return new ArrayList lt  gt                            catch  JsonSyntaxException ex                return new ArrayList lt  gt               catch  JsonParseException exc                return new ArrayList lt  gt                         return this sectionList      it works for me

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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

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Set the values intent putParcelableArrayListExtra  key  collection      Retrieve the values ArrayList lt OnlineMember gt  onlineMembers   data getParcelableArrayListExtra  key

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Also with Kotlin   fun SharedPreferences Editor putIntegerArrayList key  String  list  ArrayList lt Int gt     SharedPreferences Editor       putString key  list  joinToString                 return this    fun SharedPreferences getIntegerArrayList key  String  defValue  ArrayList lt Int gt     ArrayList lt Int gt         val value   getString key  null      if  value isNullOrBlank            return defValue     return ArrayList  value split      map   it toInt

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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      shared preferences    private SharedPreferences preferences     private SharedPreferences Editor nsuserdefaults      setup persistent data         preferences   this getSharedPreferences  MyPreferences   MainActivity MODE PRIVATE           nsuserdefaults   preferences edit             arrayOfMemberUrlsUserIsFollowing   new ArrayList lt String gt               Retrieve followers from sharedPreferences         Set lt String gt  set   preferences getStringSet  following   null            if  set    null                   lazy instantiate array             arrayOfMemberUrlsUserIsFollowing   new ArrayList lt String gt               else                  there is data from previous run             arrayOfMemberUrlsUserIsFollowing   new ArrayList lt  gt  set                 convert arraylist to set  and save arrayOfMemberUrlsUserIsFollowing to nsuserdefaults                 Set lt String gt  set   new HashSet lt String gt                     set addAll arrayOfMemberUrlsUserIsFollowing                   nsuserdefaults putStringSet  following   set                   nsuserdefaults commit

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With Kotlin  for simple arrays and lists  you can do something like   class MyPrefs context  Context        val prefs   context getSharedPreferences  x y z PREFS FILENAME   0      var listOfFloats  List lt Float gt          get     prefs getString  listOfFloats       split      map   it toFloat             set value    prefs edit   putString  listOfFloats   value joinToString       apply       and then access the preference easily   MyPrefs context  listOfFloats        val list   MyPrefs context  listOfFloats

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public class VcareSharedPreference     private static VcareSharedPreference sharePref   new VcareSharedPreference       private static SharedPreferences sharedPreferences     private static SharedPreferences Editor editor    private VcareSharedPreference         public static VcareSharedPreference getInstance Context context        if  sharedPreferences    null            sharedPreferences   context getSharedPreferences context getPackageName    Activity MODE PRIVATE           editor   sharedPreferences edit              return sharePref     public void save String KEY  String text        editor putString KEY  text       editor commit       public String getValue String PREFKEY        String text         settings   PreferenceManager getDefaultSharedPreferences context       text   sharedPreferences getString PREFKEY  null       return text    public void removeValue String KEY        editor remove KEY       editor commit       public void clearAll         editor clear        editor commit      public void saveArrayList String key  ArrayList lt ModelWelcome gt  modelCourses        Gson gson   new Gson        String json   gson toJson modelCourses       editor putString key  json       editor apply       public ArrayList lt ModelWelcome gt  getArray String key         Gson gson   new Gson        String json   sharedPreferences getString key  null       Type type   new TypeToken lt ArrayList lt ModelWelcome gt  gt            getType     return gson fromJson json  type

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You can also convert the arraylist into a String and save that in preference  private String convertToString ArrayList lt String gt  list                 StringBuilder sb   new StringBuilder                String delim                   for  String s   list                                sb append delim                   sb append s                    delim                                  return sb toString               private ArrayList lt String gt  convertToArray String string                 ArrayList lt String gt  list   new ArrayList lt String gt  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

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This method is used to store save array list -     public static void saveSharedPreferencesLogList Context context  List lt String gt  collageList                SharedPreferences mPrefs   context getSharedPreferences  PhotoCollage   context MODE PRIVATE               SharedPreferences Editor prefsEditor   mPrefs edit                Gson gson   new Gson                String json   gson toJson collageList               prefsEditor putString  myJson   json               prefsEditor commit                This method is used to retrieve array list -    public static List lt String gt  loadSharedPreferencesLogList Context context            List lt String gt  savedCollage   new ArrayList lt String gt             SharedPreferences mPrefs   context getSharedPreferences  PhotoCollage   context MODE PRIVATE           Gson gson   new Gson            String json   mPrefs getString  myJson                if  json isEmpty                  savedCollage   new ArrayList lt String gt               else               Type type   new TypeToken lt List lt String gt  gt                    getType                savedCollage   gson fromJson json  type                      return savedCollage

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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 lt 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 lt size i                sKey add mSharedPreference1 getString  Status     i  null

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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     Converting list to string new Gson   toJson list      Converting string to list new Gson   fromJson listString  CustomObjectsList class     Using Java serialization     Converting list to string ByteArrayOutputStream bos   new ByteArrayOutputStream    ObjectOutputStream oos   new ObjectOutputStream bos   oos writeObject list   oos flush    String string   Base64 encodeToString bos toByteArray    Base64 DEFAULT   oos close    bos close    return string     Converting string to list byte   bytesArray   Base64 decode familiarVisitsString  Base64 DEFAULT   ByteArrayInputStream bis   new ByteArrayInputStream bytesArray   ObjectInputStream ois   new ObjectInputStream bis   Object clone   ois readObject    ois close    bis close    return  CustomObjectsList  clone

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You can save String and custom array list using Gson library     First you need to create function to save array list to SharedPreferences   public void saveListInLocal ArrayList lt String gt  list  String key             SharedPreferences prefs   getSharedPreferences  AppName   Context MODE PRIVATE           SharedPreferences Editor editor   prefs edit            Gson gson   new Gson            String json   gson toJson list           editor putString key  json           editor apply           This line is IMPORTANT                 You need to create function to get array list from SharedPreferences   public ArrayList lt String gt  getListFromLocal String key        SharedPreferences prefs   getSharedPreferences  AppName   Context MODE PRIVATE       Gson gson   new Gson        String json   prefs getString key  null       Type type   new TypeToken lt ArrayList lt String gt  gt       getType        return gson fromJson json  type           How to call save and retrieve array list function   ArrayList lt String gt  listSave new ArrayList lt  gt     listSave add  test1     listSave add  test2     saveListInLocal listSave  key    Log e  saveArrayList    Save ArrayList success    ArrayList lt String gt  listGet new ArrayList lt  gt     listGet getListFromLocal  key    Log e  getArrayList    Get ArrayList size  listGet size          Don t forgot to add gson library in you app level build gradle   implementation  com google code gson gson 2 8 2

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

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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   public class MainActivity extends AppCompatActivity       ArrayList lt String gt  arrayList   new ArrayList lt  gt           Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity main            SharedPreferences prefs   this getSharedPreferences  com example nec myapplication   Context MODE PRIVATE            HashSet lt String gt  set   new HashSet arrayList           prefs edit   putStringSet  names   set  apply              set    HashSet lt String gt   prefs getStringSet  names   null           arrayList   new ArrayList set            Log i  array list   arrayList toString

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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 lt HttpParam gt  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 lt HttpParam gt  httpParamList     new Gson   fromJson httpParamJSONList  new TypeToken lt List lt HttpParam gt  gt                    getType

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After API 11 the SharedPreferences Editor accepts Sets  You could convert your List into a HashSet or something similar and store it like that  When you read it back  convert it into an ArrayList  sort it if needed and you re good to go    Retrieve the values Set lt String gt  set   myScores getStringSet  quot key quot   null      Set the values Set lt String gt  set   new HashSet lt String gt     set addAll listOfExistingScores   scoreEditor putStringSet  quot key quot   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 a 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  it s simpler   we have to serialize and de-serialize the ArrayList object which has the list of tasks into a 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 lt task gt           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 lt task gt                load tasks from preference   SharedPreferences prefs   getSharedPreferences SHARED PREFS FILE  Context MODE PRIVATE       try       currentTasks    ArrayList lt task gt   ObjectSerializer deserialize prefs getString TASKS  ObjectSerializer serialize new ArrayList lt task gt            catch  IOException e        e printStackTrace        catch  ClassNotFoundException e        e printStackTrace           You can get the ObjectSerializer class from the Apache Pig project ObjectSerializer java

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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 lt String gt  arrPackage    2 Variable initialization i e    shared   getSharedPreferences  App settings   MODE PRIVATE       add values for your ArrayList any where     arrPackage   new ArrayList lt  gt       3 Store value to sharedPreference using packagesharedPreferences      private void packagesharedPreferences        SharedPreferences Editor editor   shared edit       Set lt String gt  set   new HashSet lt String gt        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 lt String gt  set   shared getStringSet  DATE LIST   null      arrPackage addAll set      Log d  retrivesharedPreferences     set        I hope it will helpful for you

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Save and get ArrayList in SharedPreference       JAVA    public void saveArrayList ArrayList lt String gt  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 lt String gt  getArrayList String key       SharedPreferences prefs   PreferenceManager getDefaultSharedPreferences activity       Gson gson   new Gson        String json   prefs getString key  null       Type type   new TypeToken lt ArrayList lt String gt  gt       getType        return gson fromJson json  type       Kotlin  fun saveArrayList list  java util ArrayList lt String  gt    key  String         val prefs  SharedPreferences   PreferenceManager getDefaultSharedPreferences activity      val editor  Editor   prefs edit       val gson   Gson       val json  String   gson toJson list      editor putString key  json      editor apply      fun getArrayList key  String    java util ArrayList lt String  gt         val prefs  SharedPreferences   PreferenceManager getDefaultSharedPreferences activity      val gson   Gson       val json  String   prefs getString key  null      val type  Type   object   TypeToken lt java util ArrayList lt String  gt   gt       getType       return gson fromJson json  type

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Use this custom class   public class SharedPreferencesUtil        public static void pushStringList SharedPreferences sharedPref                                         List lt String gt  list  String uniqueListName             SharedPreferences Editor editor   sharedPref edit            editor putInt uniqueListName     size   list size              for  int i   0  i  lt  list size    i                  editor remove uniqueListName   i               editor putString uniqueListName   i  list get i                      editor apply               public static List lt String gt  pullStringList SharedPreferences sharedPref                                                 String uniqueListName             List lt String gt  result   new ArrayList lt  gt             int size   sharedPref getInt uniqueListName     size   0            for  int i   0  i  lt  size  i                  result add sharedPref getString uniqueListName   i  null                      return result            How to use   SharedPreferences sharedPref   getPreferences Context MODE PRIVATE   SharedPreferencesUtil pushStringList sharedPref  list  getString R string list name    List lt String gt  list   SharedPreferencesUtil pullStringList sharedPref  getString R string list name

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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

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don t forget to implement Serializable   Class dataBean implements Serializable   public String name    ArrayList lt dataBean gt  dataBeanArrayList   new ArrayList      https   stackoverflow com a 7635154 4639974

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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  private void serializeKey String key  Bundle bundle  SharedPreferences Editor editor      throws JSONException       Object value   bundle get key       if  value    null               Cannot serialize null values          return             String supportedType   null      JSONArray jsonArray   null      JSONObject json   new JSONObject         if  value instanceof Byte            supportedType   TYPE BYTE          json put JSON VALUE    Byte value  intValue           else if  value instanceof Short            supportedType   TYPE SHORT          json put JSON VALUE    Short value  intValue           else if  value instanceof Integer            supportedType   TYPE INTEGER          json put JSON VALUE    Integer value  intValue           else if  value instanceof Long            supportedType   TYPE LONG          json put JSON VALUE    Long value  longValue           else if  value instanceof Float            supportedType   TYPE FLOAT          json put JSON VALUE    Float value  doubleValue           else if  value instanceof Double            supportedType   TYPE DOUBLE          json put JSON VALUE    Double value  doubleValue           else if  value instanceof Boolean            supportedType   TYPE BOOLEAN          json put JSON VALUE    Boolean value  booleanValue           else if  value instanceof Character            supportedType   TYPE CHAR          json put JSON VALUE  value toString           else if  value instanceof String            supportedType   TYPE STRING          json put JSON VALUE   String value         else              Optimistically create a JSONArray  If not an array type  we can null            it out later         jsonArray   new JSONArray            if  value instanceof byte                  supportedType   TYPE BYTE ARRAY              for  byte v    byte   value                    jsonArray put  int v                           else if  value instanceof short                  supportedType   TYPE SHORT ARRAY              for  short v    short   value                    jsonArray put  int v                           else if  value instanceof int                  supportedType   TYPE INTEGER ARRAY              for  int v    int   value                    jsonArray put v                           else if  value instanceof long                  supportedType   TYPE LONG ARRAY              for  long v    long   value                    jsonArray put v                           else if  value instanceof float                  supportedType   TYPE FLOAT ARRAY              for  float v    float   value                    jsonArray put  double v                           else if  value instanceof double                  supportedType   TYPE DOUBLE ARRAY              for  double v    double   value                    jsonArray put v                           else if  value instanceof boolean                  supportedType   TYPE BOOLEAN ARRAY              for  boolean v    boolean   value                    jsonArray put v                           else if  value instanceof char                  supportedType   TYPE CHAR ARRAY              for  char v    char   value                    jsonArray put String valueOf v                            else if  value instanceof List lt   gt                 supportedType   TYPE STRING LIST               SuppressWarnings  unchecked               List lt String gt  stringList    List lt String gt  value              for  String v   stringList                    jsonArray put  v    null    JSONObject NULL   v                           else                  Unsupported type  Clear out the array as a precaution even though                it is redundant with the null supportedType              jsonArray   null                       if  supportedType    null            json put JSON VALUE TYPE  supportedType           if  jsonArray    null                   If we have an array  it has already been converted to JSON  So use                that instead              json putOpt JSON VALUE  jsonArray                      String jsonString   json toString            editor putString key  jsonString            private void deserializeKey String key  Bundle bundle          throws JSONException       String jsonString   cache getString key             JSONObject json   new JSONObject jsonString        String valueType   json getString JSON VALUE TYPE        if  valueType equals TYPE BOOLEAN             bundle putBoolean key  json getBoolean JSON VALUE          else if  valueType equals TYPE BOOLEAN ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           boolean   array   new boolean jsonArray length             for  int i   0  i  lt  array length  i                  array i    jsonArray getBoolean i                     bundle putBooleanArray key  array         else if  valueType equals TYPE BYTE             bundle putByte key   byte json getInt JSON VALUE          else if  valueType equals TYPE BYTE ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           byte   array   new byte jsonArray length             for  int i   0  i  lt  array length  i                  array i     byte jsonArray getInt i                     bundle putByteArray key  array         else if  valueType equals TYPE SHORT             bundle putShort key   short json getInt JSON VALUE          else if  valueType equals TYPE SHORT ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           short   array   new short jsonArray length             for  int i   0  i  lt  array length  i                  array i     short jsonArray getInt i                     bundle putShortArray key  array         else if  valueType equals TYPE INTEGER             bundle putInt key  json getInt JSON VALUE          else if  valueType equals TYPE INTEGER ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           int   array   new int jsonArray length             for  int i   0  i  lt  array length  i                  array i    jsonArray getInt i                     bundle putIntArray key  array         else if  valueType equals TYPE LONG             bundle putLong key  json getLong JSON VALUE          else if  valueType equals TYPE LONG ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           long   array   new long jsonArray length             for  int i   0  i  lt  array length  i                  array i    jsonArray getLong i                     bundle putLongArray key  array         else if  valueType equals TYPE FLOAT             bundle putFloat key   float json getDouble JSON VALUE          else if  valueType equals TYPE FLOAT ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           float   array   new float jsonArray length             for  int i   0  i  lt  array length  i                  array i     float jsonArray getDouble i                     bundle putFloatArray key  array         else if  valueType equals TYPE DOUBLE             bundle putDouble key  json getDouble JSON VALUE          else if  valueType equals TYPE DOUBLE ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           double   array   new double jsonArray length             for  int i   0  i  lt  array length  i                  array i    jsonArray getDouble i                     bundle putDoubleArray key  array         else if  valueType equals TYPE CHAR             String charString   json getString JSON VALUE           if  charString    null  amp  amp  charString length      1                bundle putChar key  charString charAt 0                    else if  valueType equals TYPE CHAR ARRAY             JSONArray jsonArray   json getJSONArray JSON VALUE           char   array   new char jsonArray length             for  int i   0  i  lt  array length  i                  String charString   jsonArray getString i               if  charString    null  amp  amp  charString length      1                    array i    charString charAt 0                                   bundle putCharArray key  array         else if  valueType equals TYPE STRING             bundle putString key  json getString JSON VALUE          else if  valueType equals TYPE STRING LIST             JSONArray jsonArray   json getJSONArray JSON VALUE           int numStrings   jsonArray length            ArrayList lt String gt  stringList   new ArrayList lt String gt  numStrings           for  int i   0  i  lt  numStrings  i                  Object jsonStringValue   jsonArray get i               stringList add i  jsonStringValue    JSONObject NULL   null    String jsonStringValue                     bundle putStringArrayList key  stringList

User · Answer

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

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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   editor putString genrealfeedkey j  1   Rowitemslist get j  getname             editor putString genrealfeedkey j  2   Rowitemslist get j  getdescription             editor putString genrealfeedkey j  3   Rowitemslist get j  getlink             editor putString genrealfeedkey j  4   Rowitemslist get j  getid             editor putString genrealfeedkey j  5   Rowitemslist get j  getmessage

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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  quot key quot   null   String   text   gson fromJson jsonText  String   class      EDIT  gso to gson     Set the values Gson gson   new Gson    List lt String gt  textList   new ArrayList lt String gt  data   String jsonText   gson toJson textList   prefsEditor putString  quot key quot   jsonText   prefsEditor apply

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Please use these two methods for store data in ArrayList in kotlin  fun setDataInArrayList list  ArrayList lt ShopReisterRequest gt   key  String  context  Context        val prefs   PreferenceManager getDefaultSharedPreferences context      val editor   prefs edit       val gson   Gson       val json   gson toJson list      editor putString key  json      editor apply         fun getDataInArrayList key  String  context  Context   ArrayList lt ShopReisterRequest gt        val prefs   PreferenceManager getDefaultSharedPreferences context      val gson   Gson       val json   prefs getString key  null      val type   object   TypeToken lt ArrayList lt ShopReisterRequest gt  gt             type     return gson fromJson lt ArrayList lt ShopReisterRequest gt  gt  json  type

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public  void saveUserName Context con String username                try                       usernameSharedPreferences  PreferenceManager getDefaultSharedPreferences con               usernameEditor   usernameSharedPreferences edit                usernameEditor putInt PREFS KEY SIZE  USERNAME size   1                 int size USERNAME size     USERNAME is arrayList             usernameEditor putString PREFS KEY USERNAME size username               usernameEditor commit                      catch Exception e                        e printStackTrace                         public void loadUserName Context con                  try                       usernameSharedPreferences  PreferenceManager getDefaultSharedPreferences con               size usernameSharedPreferences getInt PREFS KEY SIZE size               USERNAME clear                for int i 0 i lt size i                                   String username1                     username1 usernameSharedPreferences getString PREFS KEY USERNAME i username1                   USERNAME add username1                             usernameArrayAdapter   new ArrayAdapter lt String gt  this  android R layout simple dropdown item 1line  USERNAME               username setAdapter usernameArrayAdapter               username setThreshold 0                      catch Exception e                        e printStackTrace

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My utils class for save list to SharedPreferences  public class SharedPrefApi       private SharedPreferences sharedPreferences      private Gson gson       public SharedPrefApi Context context  Gson gson            this sharedPreferences   context getSharedPreferences PREFS NAME  Context MODE PRIVATE           this gson   gson                       public  lt T gt  void putList String key  List lt T gt  list            SharedPreferences Editor editor   sharedPreferences edit            editor putString key  gson toJson list            editor apply               public  lt T gt  List lt T gt  getList String key  Class lt T gt  clazz            Type typeOfT   TypeToken getParameterized List class  clazz  getType            return gson fromJson getString key  null   typeOfT             Using     for save sharedPrefApi putList SharedPrefApi Key USER LIST  userList       for retrieve List lt User gt  userList   sharedPrefApi getList SharedPrefApi Key USER LIST  User class       Full code of my utils    check using example in Activity code

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public static void WriteSharePrefrence1 Context context  String key   ArrayList lt HashMap lt String  String gt  gt  value        final SharedPreferences preferences        PreferenceManager getDefaultSharedPreferences context       SharedPreferences Editor editor   preferences edit        Gson gson   new Gson        String json   gson toJson value       editor putString key  json       editor commit      public static ArrayList lt HashMap lt String  String gt  gt  ReadSharePrefrence1 Context context    String key        String data      Gson gson   new Gson        ArrayList lt HashMap lt String  String gt  gt  items   new ArrayList lt  gt         final SharedPreferences preferences        PreferenceManager getDefaultSharedPreferences context       final SharedPreferences Editor editor   preferences edit        data   preferences getString key            Type type   new TypeToken lt ArrayList lt HashMap lt String  String gt  gt  gt       getType        items   gson fromJson data  type        return items

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This is your perfect solution   try it   public void saveArrayList ArrayList lt String gt  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 lt String gt  getArrayList String key       SharedPreferences prefs   PreferenceManager getDefaultSharedPreferences activity       Gson gson   new Gson        String json   prefs getString key  null       Type type   new TypeToken lt ArrayList lt String gt  gt       getType        return gson fromJson json  type

User · 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   public class MyApp extends Application          Pardon me for using global         private ArrayList lt CustomObject gt  globalArray       public void setGlobalArrayOfCustomObjects ArrayList lt CustomObject gt  newArray           globalArray   newArray              public ArrayList lt CustomObject gt  getGlobalArrayOfCustomObjects            return globalArray             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

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I have read all answers above  That is all correct but i found a more easy solution as below    Saving String List in shared-preference    public static void setSharedPreferenceStringList Context pContext  String pKey  List lt String gt  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  lt  pData size    i          SharedPreferences Editor editor1   pContext getSharedPreferences Constants APP PREFS  Activity MODE PRIVATE  edit        editor1 putString pKey   i   pData get i         editor1 commit          and for getting String List from Shared-preference    public static List lt String gt  getSharedPreferenceStringList Context pContext  String pKey    int size   pContext getSharedPreferences Constants APP PREFS  Activity MODE PRIVATE  getInt pKey    size   0   List lt String gt  list   new ArrayList lt  gt     for  int i   0  i  lt  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

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

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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  implementation  io paperdb paperdb 2 6    Initialize Paper  Should be initialized once in Application onCreate     Paper init context     Save  List lt Person gt  contacts       Paper book   write  contacts   contacts     Loading Data  Use default values if object doesn t exist in the storage   List lt Person gt  contacts   Paper book   read  contacts   new ArrayList lt  gt        Here you go   https   github com pilgr Paper

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Saving and retrieving the ArrayList From SharedPreference     public static void addToPreference String id Context context            SharedPreferences sharedPreferences   context getSharedPreferences Constants MyPreference  Context MODE PRIVATE           ArrayList lt String gt  list   getListFromPreference context           if   list contains id                 list add id               SharedPreferences Editor edit   sharedPreferences edit                Set lt String gt  set   new HashSet lt  gt                 set addAll list               edit putStringSet Constant LIST  set               edit commit                         public static ArrayList lt String gt  getListFromPreference Context context            SharedPreferences sharedPreferences   context getSharedPreferences Constants MyPreference  Context MODE PRIVATE           Set lt String gt  set   sharedPreferences getStringSet Constant LIST  null           ArrayList lt String gt  list   new ArrayList lt  gt             if  set    null                list   new ArrayList lt  gt  set                     return list

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It s very simple using getStringSet and putStringSet in SharedPreferences  but in my case  I have to duplicate the Set object before I can add anything to the Set  Or else  the Set will not be saved if my app is force closed  Probably because of the note below in the API below   It saved though if app is closed by back button        Note that you must not modify the set instance returned by this call  The consistency of the stored data is not guaranteed if you do  nor is your ability to modify the instance at all    http   developer android com reference android content SharedPreferences html getStringSet   SharedPreferences prefs   PreferenceManager getDefaultSharedPreferences getActivity     SharedPreferences Editor editor   prefs edit     Set lt String gt  outSet   prefs getStringSet  key   new HashSet lt String gt      Set lt String gt  workingSet   new HashSet lt String gt  outSet   workingSet add  Another String     editor putStringSet  key   workingSet   editor commit

[android] Save ArrayList to SharedPreferences

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