I recently researched the section of the Android developer documentation on handling application preferences using shared preferences and PreferenceFragment and made the following simple example:

SettingsActivity.java

public class SettingsActivity extends PreferenceActivity {

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

if(savedInstanceState == null)
            getFragmentManager().beginTransaction()
                .replace(android. R.id.content, new SettingsFragment())
                .commit()

}

}

SettingsFragment.java

public class SettingsFragment extends PreferenceFragment {

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings);
    }

}

res/xml/settings.xml

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

<PreferenceCategory android:title="@string/pref_general_category">    

<EditTextPreference
            android:key="@id/pref_key_apiBaseUri"
            android:title="@string/pref_apiBaseUri_title"
            android:defaultValue="@string/pref_apiBaseUri_default"
            android:persistent="true"
            android:inputType="text"
            android:singleLine="true" />

</PreferenceCategory>

</PreferenceScreen>

Other content:

id        pref_key_apiBaseUri
string    pref_apiBaseUri_title       "Api Base Uri"
string    pref_api_baseUri_default    "http://acme.com/api/

Question

Simple and clear stuff, eh? I launched the app, went to the preferences menu/activity, the preferences fragment was inflated, and I clicked on “API Base Uri“. The EditText dialog pops up, I change “http://acme.com/api” to “http://acme.com/api2” and press OK. Now, as far as I understand the documentation, preferences should be automatically saved to sharing preferences. When I reopen the EditText dialog, I see that my changes have been saved.

But…… When I close the activity (or application) and go back to the settings, the default value is back with no changes! What do I do to save my settings permanently?

In your settings.xml, you have:

<EditTextPreference
    android:key="@id/pref_key_apiBaseUri"
    android:title="@string/pref_apiBaseUri_title"
    android:defaultValue="@string/pref_apiBaseUri_default"
    android:persistent="true"
    android:inputType="text"
    android:singleLine="true" />

You must specify a string for key, as described in the documentation for android:key:

This attribute is required for preferences that persist a data value. It specifies the unique key (a string) the system uses when saving this setting’s value in the SharedPreferences.

Your pref_key_apiBaseUri appears to be an empty string. Change it to a valid string and move to strings.xml:

<string name="pref_key_apiBaseUri">KEY</string>

Then used as:

<EditTextPreference
    android:key="@string/pref_key_apiBaseUri"
    ...

Or leave it as is, just add a + before the id tag, which will create the id, which in turn will be used as the key:

<EditTextPreference
    android:key="@+id/pref_key_apiBaseUri"
    ...