/** 查询选中省内的所有的市,优先从数据库查询,如果没有查询到再去服务器上查询。 */
 private void queryCities() {
   cityList = coolWeatherDB.loadCities(selectedProvince.getId());
   if (cityList.size() > 0) {
     dataList.clear();
     for (City city : cityList) {
       dataList.add(city.getCityName());
     }
     adapter.notifyDataSetChanged();
     listView.setSelection(0);
     titleText.setText(selectedProvince.getProvinceName());
     currentLevel = LEVEL_CITY;
   } else {
     queryFromServer(selectedProvince.getProvinceCode(), "city");
   }
 }
 /** 查询全国所有的省,优先从数据库查询,如果没有查询到再去服务器上查询。 */
 private void queryProvinces() {
   provinceList = coolWeatherDB.loadProvince();
   if (provinceList.size() > 0) {
     dataList.clear();
     for (Province province : provinceList) {
       dataList.add(province.getProvinceName());
     }
     adapter.notifyDataSetChanged();
     listView.setSelection(0);
     titleText.setText("中国");
     currentLevel = LEVEL_PROVINCE;
   } else {
     queryFromServer(null, "province");
   }
 }