How do you validate the format and values of EditTextPreference entered in Android 2.1?

Question

Does anyone have sample code to validate user entered text in preferences? For example, I have a EditTextPreference for user to enter an email address. I\'d like to validate

Answer 1

I'd use Preference.OnPreferenceChangeListener rather than SharedPreferences.OnSharedPreferenceChangeListener.

The former allows you to validate the new value before it's persisted (and prevent it from being persisted) rather than after.

Answer 2

Implement Preference.OnPreferenceChangeListener

boolean onPreferenceChange(Preference preference, Object newValue)

Called when a Preference has been changed by the user. This is called before the state of the Preference is about to be updated and before the state is persisted.

Returns True to update the state of the Preference with the new value.

So you can directly return the result of value validation.

public class Preferences extends PreferenceActivity implements OnSharedPreferenceChangeListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
        findPreference("mail_preference_key").setOnPreferenceChangeListener(
            new Preference.OnPreferenceChangeListener() {

            @Override
            public boolean onPreferenceChange(Preference preference, Object newValue) {
                return Pattern.matches("mailPattern", (String) newValue);
            }

        });
    }
}

Answer 3

Your question was an early google hit when I was trying to do the same thing, so hopefully this helps someone. Here's something I hacked together today that demonstrates OnPreferenceChangeListener, thus allowing you to stop invalid changes.

in your fragment:

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

        Your_Pref = (EditTextPreference) getPreferenceScreen().findPreference("Your_Pref");

        Your_Pref.setOnPreferenceChangeListener(new OnPreferenceChangeListener() {

            @Override
            public boolean onPreferenceChange(Preference preference, Object newValue) {
                Boolean rtnval = true;
                if (Your_Test) {
                    final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
                    builder.setTitle("Invalid Input");
                    builder.setMessage("Something's gone wrong...");
                    builder.setPositiveButton(android.R.string.ok, null);
                    builder.show();
                    rtnval = false;
                }
                return rtnval;
            }
        });
    }