Long time, no post.. I’ve been waay too busy programming Android for the last few weeks to get anything useful done. As mentioned a few days ago, I’m getting deluged by weird comment spam, so comments are turned off for the moment – sorry.
Today I was trying to mix Android’s two storage mechanisms. The application needs to store a small number of settings which a user can create/update/delete - a database. Additionally, one of these settings is considered to be “selected” – probably SharedPreferences, though one could argue for the database here too. My first intuition was to specialize a subclass of ListPreference to override the getEntries() and getEntryValues() methods – nope. The next idea was to call setEntries(CharSequence[]) and setEntryValues(CharSequence[]) in the constuctor – that seems to work fine. However, since I was reading from a database, I wanted the Cursor to be managed by an activity. Since I was subclassing ListPreference, that wasn’t gonna work. Ultimately, I settled on subclassing PreferenceActivity and building the menus in code instead of XML. Adapting the sample database code from Notepadv3, here is a custom Preferences menu:
public class EditPreferences extends PreferenceActivity { public static final String SELECTED_TARGET_KEY = "SelectedTargetKey"; public static final String NO_SELECTION = "0"; private TargetDbAdapter mDbHelper; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setPreferenceScreen(createPreferenceHierarchy()); } private PreferenceScreen createPreferenceHierarchy() { PreferenceScreen root = getPreferenceManager().createPreferenceScreen(this); PreferenceCategory dialogBasedPrefCat = new PreferenceCategory(this); dialogBasedPrefCat.setTitle(R.string.pref_cat_title); root.addPreference(dialogBasedPrefCat); //builds list from DB mDbHelper = new TargetDbAdapter(this); mDbHelper.open(); Cursor c = mDbHelper.fetchAllNotes(); startManagingCursor(c); int count = c.getCount(); CharSequence[] entries = new CharSequence[count]; CharSequence[] entryValues = new CharSequence[count]; c.moveToFirst(); for(int i=0; i<count; i++) { entries[i] = c.getString(c.getColumnIndexOrThrow(TargetDbAdapter.KEY_TITLE)); entryValues[i] = c.getString(c.getColumnIndexOrThrow(TargetDbAdapter.KEY_ROWID)); c.moveToNext(); } ListPreference targets = new ListPreference(this); targets.setEntries(entries); targets.setEntryValues(entryValues); targets.setDefaultValue(NO_SELECTION); targets.setDialogTitle(R.string.pref_dialog_title); targets.setKey(SELECTED_TARGET_KEY); targets.setTitle(R.string.pref_title); targets.setSummary(R.string.pref_summary); dialogBasedPrefCat.addPreference(targets); //add other preference screens return root; } }