Android - Using Shared Preferences in separate class?

Question

I want to save data using Shared Preferences in android. But I am looking to use separate class to do this task. I have implemented that class like below,

import android.content.Context;
import android.content.SharedPreferences;

public class SavePref {

    private Context context;

    public SavePref(Context context){
        this.context = context;
    }

    public void saveInt(String key, int value) {

        SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPref.edit();
        editor.putInt(key, value);
        editor.commit();

    }

}

But there is an error on getActivity(),

The method getActivity() is undefined for the type SavePref

How to solve this?
Thanks

Answer 1

getActivity() is a method of Fragment not of your SavePref. In your case the simple fix is to use the Context you are keeping as member variable to retrieve the SharedPreferences. An alternative to your approach is to avoid keeping the context as member variable, linking somehow the shared preferences to an instance of of your SavePref class, and have a static method

  public static void saveInt(Context context, String key, int value) {
        SharedPreferences sharedPref = context.getDefaultSharedPreferences(Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPref.edit();
        editor.putInt(key, value);
        editor.commit();
    }

and address the method like:

SavePref.saveInt(getActivity(), key, value);

from a Fragment or

SavePref.saveInt(this, key, value);

from an Activity. This way you don't need to instantiate SavePref every time you need to call saveInt, and you can avoid to store a reference to the Context.

Answer 2

I have created a class to do the same thing. This way you can save boolean, int, string data or check if data has been saved in a specific group of preferences for your app.

So, you need to create a class "DataProccessor.java" and put the content down bellow. Also I'm going to leave some examples about how to use it.

I hope it can helps you

import android.content.Context;
import android.content.SharedPreferences;

public class DataProccessor {

    private static Context context;

    public DataProccessor(Context context){
        this.context = context;
    }

    public final static String PREFS_NAME = "appname_prefs";

    public boolean sharedPreferenceExist(String key)
    {
        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, 0);
        if(!prefs.contains(key)){
            return true;
        }
        else {
            return false;
        }
    }

    public static void setInt( String key, int value) {
        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME,0);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putInt(key, value);
        editor.apply();
    }

    public static int getInt(String key) {
        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, 0);
        return prefs.getInt(key, 0);
    }

    public static void setStr(String key, String value) {
        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME,0);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putString(key, value);
        editor.apply();
    }

    public static String getStr(String key) {
        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, 0);
        return prefs.getString(key,"DNF");
    }

    public static void setBool(String key, boolean value) {
        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME,0);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putBoolean(key, value);
        editor.apply();
    }

    public static boolean getBool(String key) {
        SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, 0);
        return prefs.getBoolean(key,false);
    }
}

To use it I'll show you some small examples about how to save a String value in case you want to use it in an Activity, Fragment or Service.

For an Activity

 //// To Save a value
 DataProccessor dataProccessor = new DataProccessor(this);
 dataProccessor.setStr("email","[email protected]");

 //// To Retreive a value
 dataProccessor.getStr("email");

For a Fragment

 //// To Save a value
 DataProccessor dataProccessor = new DataProccessor(getActivity());
 dataProccessor.setStr("email","[email protected]");

 //// To Retreive a value
 dataProccessor.getStr("email");

For a Service

 //// To Save a value
 DataProccessor dataProccessor = new DataProccessor(getApplicationContext());
 dataProccessor.setStr("email","[email protected]");

 //// To Retreive a value
 dataProccessor.getStr("email");