Professional Android 4 Application Development

238 x CHAPTER 7 FILES, SAVING STATE,AND PREFERENCES
Finding and Using the Shared Preferences
Set by Preference Screens
The Shared Preference values recorded for the options presented in a Preference Activity are stored
within the application’s sandbox. This lets any application component, including Activities, Services,
and Broadcast Receivers, access the values, as shown in the following snippet:
Context context = getApplicationContext();
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
// TODO Retrieve values using get methods.
Introducing On Shared Preference Change Listeners
The onSharedPreferenceChangeListener can be implemented to invoke a callback whenever a
particular Shared Preference value is added, removed, or modified.
This is particularly useful for Activities and Services that use the Shared Preference framework to
set application preferences. Using this handler, your application components can listen for changes
to user preferences and update their UIs or behavior, as required.
Register your On Shared Preference Change Listeners using the Shared Preference you want
to monitor:
public class MyActivity extends Activity implements
OnSharedPreferenceChangeListener {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
// Register this OnSharedPreferenceChangeListener
SharedPreferences prefs =
PreferenceManager.getDefaultSharedPreferences(this);
prefs.registerOnSharedPreferenceChangeListener(this);
public void onSharedPreferenceChanged(SharedPreferences prefs,
String key) {
// TODO Check the shared preference and key parameters
// and change UI or behavior as appropriate.
}
CREATING A STANDARD PREFERENCE ACTIVITY FOR THE
EARTHQUAKE VIEWER
Previously in this chapter you created a custom Activity to let users modify the application settings
for the earthquake viewer. In this example you replace this custom Activity with the standard application
settings framework described in the previous section.