Preferences.java 文件源码

@Override
public boolean onPreferenceChange(Preference preference, Object value) {
    String stringValue = value.toString();
    if (preference instanceof ListPreference) {
        ListPreference listPreference = (ListPreference) preference;
        int index = listPreference.findIndexOfValue(stringValue);
        preference.setSummary(
                index >= 0
                        ? listPreference.getEntries()[index]
                        : null);

    } else if (preference instanceof RingtonePreference) {
        // For ringtone preferences, look up the correct display value
        // using RingtoneManager.
        if (TextUtils.isEmpty(stringValue)) {
            // Empty values correspond to 'silent' (no ringtone).
            preference.setSummary(R.string.pref_ringtone_silent);

        } else {
            Ringtone ringtone = RingtoneManager.getRingtone(
                    preference.getContext(), Uri.parse(stringValue));

            if (ringtone == null) {
                // Clear the summary if there was a lookup error.
                preference.setSummary(null);
            } else {
                // Set the summary to reflect the new ringtone display
                // name.
                String name = ringtone.getTitle(preference.getContext());
                preference.setSummary(name);
            }
        }

    } else {
        // For all other preferences, set the summary to the value's
        // simple string representation.
        preference.setSummary(stringValue);
    }
    return true;
}