what is the Best way to use shared preferences between activities

Question

I have a user preference in my app, which gets used by different activities. I would like to know the best way to utilize those preferences between different activities in m

Answer 1

Sending shared preferences through intents seems overcomplicated. You could wrap the shared preferences with something like the below and call the methods directly from your activities:

public class Prefs {
    private static String MY_STRING_PREF = "mystringpref";
    private static String MY_INT_PREF = "myintpref";

    private static SharedPreferences getPrefs(Context context) {
        return context.getSharedPreferences("myprefs", 0);
    }

    public static String getMyStringPref(Context context) {
        return getPrefs(context).getString(MY_STRING_PREF, "default");
    }

    public static int getMyIntPref(Context context) {
        return getPrefs(context).getInt(MY_INT_PREF, 42);
    }

    public static void setMyStringPref(Context context, String value) {
        // perform validation etc..
        getPrefs(context).edit().putString(MY_STRING_PREF, value).commit();
    }

    public static void setMyIntPref(Context context, int value) {
        // perform validation etc..
        getPrefs(context).edit().putInt(MY_INT_PREF, value).commit();
    }
}

Answer 2

You can use this way and declare same variables with same name in all activites where you want to use.

  public static final String PREFS_NAME = "MyPrefsFile";
  static SharedPreferences settings;
  SharedPreferences.Editor editor;
  int wordCount;

 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    settings = getSharedPreferences(PREFS_NAME, 0);
    editor = settings.edit();

    wordCount = settings.getInt("wordCount", 4); 

  }

Here initially wordCount will give 4; And when you edit wordCount and want to store again

  editor.putInt("wordCount", 6);
  editor.commit();

You have to declare this same variables in activities where you want to use shared preferences. And its better you call getSharedPreferences in every activity.

I don't think that passing that preference in intent will work.

Answer 3

Here's a nice & easy solution in Kotlin – just copy & paste the code into a new AppPreferences.kt file and follow the 4 TODO steps outlined in the code:

import android.content.Context
import android.content.Context.MODE_PRIVATE
import android.content.SharedPreferences
import androidx.core.content.edit

object AppPreferences {
    private var sharedPreferences: SharedPreferences? = null

    // TODO step 1: call `AppPreferences.setup(applicationContext)` in your MainActivity's `onCreate` method
    fun setup(context: Context) {
        // TODO step 2: set your app name here
        sharedPreferences = context.getSharedPreferences("<YOUR_APP_NAME>.sharedprefs", MODE_PRIVATE)
    }

    // TODO step 4: replace these example attributes with your stored values
    var heightInCentimeters: Int?
        get() = Key.HEIGHT.getInt()
        set(value) = Key.HEIGHT.setInt(value)

    var birthdayInMilliseconds: Long?
        get() = Key.BIRTHDAY.getLong()
        set(value) = Key.BIRTHDAY.setLong(value)

    private enum class Key {
        HEIGHT, BIRTHDAY; // TODO step 3: replace these cases with your stored values keys

        fun getBoolean(): Boolean? = if (sharedPreferences!!.contains(name)) sharedPreferences!!.getBoolean(name, false) else null
        fun getFloat(): Float? = if (sharedPreferences!!.contains(name)) sharedPreferences!!.getFloat(name, 0f) else null
        fun getInt(): Int? = if (sharedPreferences!!.contains(name)) sharedPreferences!!.getInt(name, 0) else null
        fun getLong(): Long? = if (sharedPreferences!!.contains(name)) sharedPreferences!!.getLong(name, 0) else null
        fun getString(): String? = if (sharedPreferences!!.contains(name)) sharedPreferences!!.getString(name, "") else null

        fun setBoolean(value: Boolean?) = value?.let { sharedPreferences!!.edit { putBoolean(name, value) } } ?: remove()
        fun setFloat(value: Float?) = value?.let { sharedPreferences!!.edit { putFloat(name, value) } } ?: remove()
        fun setInt(value: Int?) = value?.let { sharedPreferences!!.edit { putInt(name, value) } } ?: remove()
        fun setLong(value: Long?) = value?.let { sharedPreferences!!.edit { putLong(name, value) } } ?: remove()
        fun setString(value: String?) = value?.let { sharedPreferences!!.edit { putString(name, value) } } ?: remove()

        fun remove() = sharedPreferences!!.edit { remove(name) }
    }
}

Answer 4

You can of course use shared preferences in your applications.

If you have more than a simple type than string or int, you can use a singleton or extends the application class which will be accessible by all activities of your application. => No disk access here. Simply kept in memory.