Weird problem with Shared Preferences in Android

Question

I am trying to use shared preferences to store my apps settings, but even though i tried to copy tutorial best as i can i still can't make it work. Here are parts of my class:

public class ActivitySettings extends PreferenceActivity {

@SuppressWarnings("unused")
private static String TAG = "ActivitySettings";

private static final String PREFS_NAME = "preferences";

private static final String DISABLE_CHECK = "disableCheck";
private static final String ALWAYS_CONFIRM = "alwaysConfirm";
private static final String NEVER_CONFIRM = "neverConfirm";
private static final String SHOW_NOTIFICATION = "showNotification";
private static final String SHOW_ON_BOOT = "showOnBoot";
private static final String HIDE_ICON = "hideIcon";
private static final String LOGGING = "logging";

private Context context = this;

private CheckBoxPreference disableCodeCheck;
private CheckBoxPreference alwaysAskForConf;
private CheckBoxPreference neverAskForConf;
private CheckBoxPreference showNotif;
private CheckBoxPreference showAtBoot;
private CheckBoxPreference hideIcon;
private Preference exportData;
private Preference importData;
private Preference cleanUp;
private Preference reset;
private CheckBoxPreference logging;

private boolean isDisableCodeCheck;
private boolean isAlwaysAskForConf;
private boolean isNeverAskForConf;
private boolean isShowNotif;
private boolean isShowAtBoot;
private boolean isHideIcon;
private boolean isLogging;

private void loadPreferences() {
    SharedPreferences prefs = getSharedPreferences(PREFS_NAME, 0);

    isDisableCodeCheck = prefs.getBoolean(DISABLE_CHECK, false);
    isAlwaysAskForConf = prefs.getBoolean(ALWAYS_CONFIRM, false);
    isNeverAskForConf = prefs.getBoolean(NEVER_CONFIRM, false);
    isShowNotif = prefs.getBoolean(SHOW_NOTIFICATION, false);
    isShowAtBoot = prefs.getBoolean(SHOW_ON_BOOT, false);
    isHideIcon = prefs.getBoolean(HIDE_ICON, false);
    isLogging = prefs.getBoolean(LOGGING, false);
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    addPreferencesFromResource(R.xml.settings);

    disableCodeCheck = (CheckBoxPreference) findPreference("disable_code_check");
    alwaysAskForConf = (CheckBoxPreference) findPreference("always_ask_for_conf");
    neverAskForConf = (CheckBoxPreference) findPreference("never_ask_for_conf");
    showNotif = (CheckBoxPreference) findPreference("show_notif");
    showAtBoot = (CheckBoxPreference) findPreference("show_at_boot");
    hideIcon = (CheckBoxPreference) findPreference("hide_icon");
    exportData = findPreference("exp");
    importData = findPreference("imp");
    cleanUp = findPreference("clean_up");
    reset = findPreference("reset");
    logging = (CheckBoxPreference) findPreference("logging");

    loadPreferences();

    //here are also booleans modified

@Override
protected void onStop() {
    super.onStop();
    savePreferences();
}

private void savePreferences() {
    SharedPreferences prefs = getSharedPreferences(PREFS_NAME, 0);

    prefs.edit().putBoolean(DISABLE_CHECK, isDisableCodeCheck);
    prefs.edit().putBoolean(ALWAYS_CONFIRM, isAlwaysAskForConf);
    prefs.edit().putBoolean(NEVER_CONFIRM, isNeverAskForConf);
    prefs.edit().putBoolean(SHOW_NOTIFICATION, isShowNotif);
    prefs.edit().putBoolean(SHOW_ON_BOOT, isShowAtBoot);
    prefs.edit().putBoolean(HIDE_ICON, isHideIcon);
    prefs.edit().putBoolean(LOGGING, isLogging);

    prefs.edit().commit();
}

}

Here is what happens:

1. there are two files created in shared_prefs: preferences.xml and packagename_preferences.xml. Don't know why, PREFS_NAME is provided.

2. loading settings is done in onCreate methos, saving and commiting in onStop

3. using adb shell and cat i'm looking into files while app is running and here is the scenario:

   • i open settings and tick sth and packagename_preferences.xml is created with correct value
   • i press back and second file is created - preferences.xml which looks like this: <?xml version='1.0' encoding='utf-8' standalone='yes' ?> <map />
   • when i open settings again everything looks like on first run and values in packagename_preferences.xml are changed to default(?)

4. i know there is and built in mechanism for PreferenceActivity but i don't want to use it because I need access to other settings from other activities.

---

EDIT

---

I have created such app:

package pl.test;

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;

public class TestActivity extends Activity {
String s = "0";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    SharedPreferences sp = getSharedPreferences("pref", 0);  
    s = sp.getString("setting2", "1");
    s = "5";
}

@Override
public void onStop() {
    super.onStop();
    SharedPreferences sp = getSharedPreferences("pref", 0);
    sp.edit().putString("setting2", s);
    sp.edit().commit();
}

}

And it doesn't work it just does not save string to pref.xml. What is wrong!?

Answer 1

While reading world readable data shared by first app, we should

Replace

getSharedPreferences("PREF_NAME", Context.MODE_PRIVATE);

with

getSharedPreferences("PREF_NAME", Context.MODE_MULTI_PROCESS);

in second app to get updated value in second app.

Answer 2

Your problem is the fact that you are generating a new Editor object with every call to sp.edit(). So your call sp.edit().commit() is creating a new editor that has no changes to commit. Try this:

private void savePreferences() {
    SharedPreferences prefs = getSharedPreferences(PREFS_NAME, 0);
    SharedPreferences.Editor editor = prefs.edit(); 
    editor.putBoolean(DISABLE_CHECK, isDisableCodeCheck);
    editor.putBoolean(ALWAYS_CONFIRM, isAlwaysAskForConf);
    editor.putBoolean(NEVER_CONFIRM, isNeverAskForConf);
    editor.putBoolean(SHOW_NOTIFICATION, isShowNotif);
    editor.putBoolean(SHOW_ON_BOOT, isShowAtBoot);
    editor.putBoolean(HIDE_ICON, isHideIcon);
    editor.putBoolean(LOGGING, isLogging);
    editor.commit();
}

Alternatively, The editor methods are designed to be chained, so this would also work:

private void savePreferences() {
    SharedPreferences prefs = getSharedPreferences(PREFS_NAME, 0)
        prefs.edit().putBoolean(DISABLE_CHECK, isDisableCodeCheck)
        .putBoolean(ALWAYS_CONFIRM, isAlwaysAskForConf)
        .putBoolean(NEVER_CONFIRM, isNeverAskForConf)
        .putBoolean(SHOW_NOTIFICATION, isShowNotif)
        .putBoolean(SHOW_ON_BOOT, isShowAtBoot)
        .putBoolean(HIDE_ICON, isHideIcon)
        .putBoolean(LOGGING, isLogging)
        .commit();
}

You have the same problem in your test code, which can be fixed like so:

@Override
public void onStop() {
    super.onStop();
    SharedPreferences sp = getSharedPreferences("pref", 0);
    sp.edit().putString("setting2", s).commit();
}