Android : How are changes in the Preference ie Checkbox Preference , List Preference etc.. saved in the Shared Preference?

Okay so I'm trying to make sense of how Shared Preference works with Preference.

Below is part of an app that works, but I do not understand how it works for the part of Shared Preference.

I have a UserPrefActivity.java containing the following code

public class UserPrefActivity extends PreferenceActivity {
    //a preference value change listener that updates the preference summary
    //to reflect its new value
    private static Preference.OnPreferenceChangeListener
            sBindPreferenceSummaryToValueListerner = new Preference.OnPreferenceChangeListener() {
        @Override
        public boolean onPreferenceChange(Preference preference, Object newValue) {


            //gets string value of object
            String value = newValue.toString();
            Log.e("in sBind Listener", value);
            //if the preference is a list preference, get the value at a given index
            if (preference instanceof ListPreference) {
                //for list preference look up the correct display value
                //in the preference entries array
                ListPreference listPreference = (ListPreference) preference;
                int index = listPreference.findIndexOfValue(value);

                //set the summary to reflect the new value
                preference.setSummary(index >= 0 ? listPreference.getEntries()[index] : null);
            } else {
                //set summary to only value
                preference.setSummary(value);
            }

            return true;
        }
    };


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

        //call the deprecated method to load the preference screen
        addPreferencesFromResource(R.xml.user_pref);

        //get default Shared preference from preference screen
        SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(this);



        Preference saveNumPizza = findPreference("saveNumPizza");

        //set the preference change listener to  saveNumPizza

        saveNumPizza.setOnPreferenceChangeListener(sBindPreferenceSummaryToValueListerner);




        sBindPreferenceSummaryToValueListerner.onPreferenceChange(saveNumPizza,
                PreferenceManager
                        .getDefaultSharedPreferences(this)
                        .getString(saveNumPizza.getKey(), ""));


    }


}

In the MainActivity.java, I have the following as part of a bigger piece of code

     //gets the default shared preference instance and assign to sharedPrefs for enabled save
            // data
            SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences
                    (MainActivity.this);



            //checks if save order status is true
            if (sharedPrefs.getBoolean("saveOrder", false)) {
//do stuff..
    }

I have the following UserPref.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">


    <CheckBoxPreference

        android:defaultValue="false"
        android:key="saveOrder"
        android:summary="for quick loading of favourite order"
        android:title="Enable Saving Order"/>
    <PreferenceCategory android:title="ORDER HISTORY">
        <CheckBoxPreference
            android:defaultValue="false"
            android:key="keepHistory"
            android:summary="of pizza orders"
            android:title="Keep History"/>

        <ListPreference
            android:defaultValue="3"
            android:dialogTitle="Choose how many to save"
            android:entries="@array/number_of_pizza"
            android:entryValues="@array/number_of_pizza_values"
            android:summary="3 pizza orders"
            android:key="saveNumPizza"
            android:title="Number of Orders"/>

    </PreferenceCategory>

</PreferenceScreen>

I know that in the UserPrefsActivity, I believe in the PreferenceManager.getDefaultSharedPreferences(this) call, the shared preferences is created and obtained if it does not exist, if it does its just obtained.

From what I've noticed with the app, is that on first launch when I get to the settings and launch the UserPrefActivity via intent, the shared preference of the UserPrefActivity is created, containing only the saveNumPizza key. However the minute I click on the other preferences (Checkbox preference) when I look at the shared preference file, I immediately see that the saveOrder key and keepHistory key are automatically saved.

I would just like to know how this automatic saving is exactly done since I am not using an editor to save it to the shared preference, nor am I calling apply or commit.

Thank you,