Android SharedPreferences Singleton Example

An example of SharedPreferences Singleton class in Android.

Java

public class SharePref {
    private static SharePref sharePref = new SharePref();
    private static SharedPreferences sharedPreferences;
    private static SharedPreferences.Editor editor;

    private static final String PLACE_OBJ = "place_obj";

    private SharePref() {} //prevent creating multiple instances by making the constructor private

    //The context passed into the getInstance should be application level context.
    public static SharePref getInstance(Context context) {
        if (sharedPreferences == null) {
            sharedPreferences = context.getSharedPreferences(context.getPackageName(), Activity.MODE_PRIVATE);
            editor = sharedPreferences.edit();
        }
        return sharePref;
    }

    public void savePlaceObj(String placeObjStr) {
        editor.putString(PLACE_OBJ, placeObjStr);
        editor.commit();
    }

    public String getPlaceObj() {
        return sharedPreferences.getString(PLACE_OBJ, "");
    }

    public void removePlaceObj() {
        editor.remove(PLACE_OBJ);
        editor.commit();
    }

    public void clearAll() {
        editor.clear();
        editor.commit();
    }

}

Kotlin

import android.app.Activity
import android.content.Context
import android.content.SharedPreferences

class SharedPref private constructor() {

    companion object {
        private val sharePref = SharedPref()
        private lateinit var sharedPreferences: SharedPreferences

        private val PLACE_OBJ = "place_obj"

        fun getInstance(context: Context): SharedPref {
            if (!::sharedPreferences.isInitialized) {
                synchronized(SharedPref::class.java) {
                    if (!::sharedPreferences.isInitialized) {
                        sharedPreferences = context.getSharedPreferences(context.packageName, Activity.MODE_PRIVATE)
                    }
                }
            }
            return sharePref
        }
    }

    val placeObj: String
        get() = sharedPreferences.getString(PLACE_OBJ, "")

    fun savePlaceObj(placeObjStr: String) {
        sharedPreferences.edit()
            .putString(PLACE_OBJ, placeObjStr)
            .apply()
    }

    fun removePlaceObj() {
        sharedPreferences.edit().remove(PLACE_OBJ).apply()
    }

    fun clearAll() {
        sharedPreferences.edit().clear().apply()
    }

}