Beginning Android

And you will need to arrange to invoke the activity, such as from a menu option, here pulled from SimplePrefsDemo at http://apress.com:

@Override
public boolean onCreateOptionsMenu (Menu menu) {
 menu.add(Menu.NONE, EDIT_ID, Menu.NONE, 'Edit Prefs')
  .setIcon(R.drawable.misc)
  .setAlphabeticShortcut('e');
 menu.add(Menu.NONE, CLOSE_ID, Menu.NONE, 'Close')
  .setIcon(R.drawable.eject)
  .setAlphabeticShortcut('c');
 return(super.onCreateOptionsMenu (menu));
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
 switch (item.getItemId()) {
  case EDIT_ID:
   startActivity(new Intent(this, EditPreferences.class));
   return(true);
  case CLOSE_ID:
   finish();
   return(true);
 }
 return(super.onOptionsItemSelected (item));
}

However, that is all that is needed, and it really is not that much code outside of the preferences XML. What you get for your effort is an Android-supplied preference UI, as shown in Figure 17-1.

Figure 17-1. The Simple project’s preferences UI

The checkbox can be directly checked or unchecked. To change the ringtone preference, just click on the entry in the preference list to bring up a selection dialog like the one in Figure 17-2.

Figure 17-2. Choosing a ringtone preference

Note that there is no explicit Save or Commit button or menu — changes are persisted as soon as they are made.

The SimplePrefsDemo activity, beyond having the aforementioned menu, also displays the current preferences via a TableLayout:

<?xml version='1.0' encoding='utf-8'?>
<TableLayout
 xmlns:android='http://schemas.android.com/apk/res/android'
 android:layout_width='fill_parent'
 android:layout_height='fill_parent'
>
 <TableRow>
  <TextView
   android:text='Checkbox:'
   android:paddingRight='5px'
  />
  <TextView android:id='@+id/checkbox'
  />
 </TableRow>
 <TableRow>
  <TextView
   android:text='Ringtone:'
   android:paddingRight='5px'
  />
  <TextView android:id='@+id/ringtone'
  />
 </TableRow>
</TableLayout>

The fields for the table are found in onCreate():

@Override
public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 checkbox = (TextView)findViewById(R.id.checkbox);
 ringtone = (TextView)findViewById(R.id.ringtone);
}

The fields are updated on each onResume():

@Override
public void onResume() {
 super.onResume();
 SharedPreferences prefs = PreferenceManager
  .getDefaultSharedPreferences(this);
 checkbox.setText(new Boolean(prefs
  .getBoolean('checkbox', false)).toString());
 ringtone.setText(prefs.getString('ringtone', '<unset>'));
}

This means the fields will be updated when the activity is opened and after the preferences activity is left (e.g., via the back button); see Figure 17-3.

Figure 17-3. The Simple project’s list of saved preferences

Adding a Wee Bit o’ Structure

If you have a lot of preferences for users to set, having them all in one big list may become troublesome. Android’s preference framework gives you a few ways to impose a bit of structure on your bag of preferences,