Android SharedPreferences保存第一次的信息

private void setHomeTimeZone() {
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
String homeTimeZone = prefs.getString(SettingsActivity.KEY_HOME_TZ, "");
if (!homeTimeZone.isEmpty()) {
return;
}
homeTimeZone = TimeZone.getDefault().getID();
SharedPreferences.Editor editor = prefs.edit();
editor.putString(SettingsActivity.KEY_HOME_TZ, homeTimeZone);
editor.apply();
Log.v(LOG_TAG, "Setting home time zone to " + homeTimeZone);
}