1.选择城市

public class CoolWeatherOpenHelper extends SQLiteOpenHelper {
	/**
	 * Province表建表语句
	 */
	public static final String CREATE_PROVINCE = "create table Province ("
			+ "id integer primary key autoincrement, " + "province_name text)";
	/**
	 * City表建表语句
	 */
	public static final String CREATE_CITY = "create table City ("
			+ "id integer primary key autoincrement, " + "city_name text, "
			+ "city_code text, " + "province_id integer)";
	/**
	 * 创建选中城市的表
	 */
	public static final String CREATE_ADDCITY = "create table AddCity("
			+ "id integer primary key autoincrement,"
			+ " city_name char(10) UNIQUE )";
	public CoolWeatherOpenHelper(Context context, String name,
			CursorFactory factory, int version) {
		super(context, name, factory, version);
	}
	@Override
	public void onCreate(SQLiteDatabase db) {
		db.execSQL(CREATE_PROVINCE); // 创建Province表
		db.execSQL(CREATE_CITY); // 创建City表
		db.execSQL(CREATE_ADDCITY);// 创建选中城市表
	}
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
	}
}

public class CoolWeatherDB {
	/**
	 * 数据库名
	 */
	public static final String DB_NAME = "cool_weather";
	/**
	 * 数据库版本
	 */
	public static final int VERSION = 1;
	private static CoolWeatherDB coolWeatherDB;
	private SQLiteDatabase db;
	private String cityName;
	/**
	 * 将构造方法私有化
	 */
	private CoolWeatherDB(Context context) {
		CoolWeatherOpenHelper dbHelper = new CoolWeatherOpenHelper(context,
				DB_NAME, null, VERSION);
		db = dbHelper.getWritableDatabase();
	}
	/**
	 * 获取CoolWeatherDB的实例。
	 */
	public synchronized static CoolWeatherDB getInstance(Context context) {
		if (coolWeatherDB == null) {
			coolWeatherDB = new CoolWeatherDB(context);
		}
		return coolWeatherDB;
	}
	/**
	 * 选中的城市添加到数据库
	 */
	public void saveAddCity(AddCity addCity) {
		if (addCity != null) {
			ContentValues values = new ContentValues();
			try {
				values.put("city_name", addCity.getCityName());
				db.insert("AddCity", null, values);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
	/**
	 * 读取保存的城市
	 */
	public List<AddCity> loadAddCity() {
		List<AddCity> list = new ArrayList<AddCity>();
		Cursor cursor = db.query("AddCity", null, null, null, null, null, null);
		if (cursor.moveToFirst()) {
			do {
				AddCity addCity = new AddCity();
				addCity.setCityName(cursor.getString(cursor
						.getColumnIndex("city_name")));
				list.add(addCity);
			} while (cursor.moveToNext());
		}
		return list;
	}
	/**
	 * 删除addcity表中的数据
	 */
	public void removeCity(String name) {
		int i = db.delete("AddCity", " city_name=?", new String[] { name });
		System.out.println("i--" + i);
	}
	/**
	 * 将Province实例存储到数据库。
	 */
	public void saveProvince(Province province) {
		if (province != null) {
			ContentValues values = new ContentValues();
			values.put("province_name", province.getProvinceName());
			db.insert("Province", null, values);
		}
	}
	/**
	 * 从数据库读取全国所有的省份信息。
	 */
	public List<Province> loadProvinces() {
		List<Province> list = new ArrayList<Province>();
		Cursor cursor = db
				.query("Province", null, null, null, null, null, null);
		if (cursor.moveToFirst()) {
			do {
				Province province = new Province();
				province.setId(cursor.getInt(cursor.getColumnIndex("id")));
				province.setProvinceName(cursor.getString(cursor
						.getColumnIndex("province_name")));
				list.add(province);
			} while (cursor.moveToNext());
		}
		return list;
	}
	/**
	 * 将City实例存储到数据库。
	 */
	public void saveCity(City city) {
		if (city != null) {
			ContentValues values = new ContentValues();
			values.put("city_name", city.getCityName());
			values.put("city_code", city.getCityCode());
			values.put("province_id", city.getProvinceId());
			db.insert("City", null, values);
		}
	}
	/**
	 * 从数据库读取某省下所有的城市信息。
	 */
	public List<City> loadCities(int provinceId) {
		List<City> list = new ArrayList<City>();
		Cursor cursor = db.query("City", null, "province_id = ?",
				new String[] { String.valueOf(provinceId) }, null, null, null);
		if (cursor.moveToFirst()) {
			do {
				City city = new City();
				city.setId(cursor.getInt(cursor.getColumnIndex("id")));
				city.setCityName(cursor.getString(cursor
						.getColumnIndex("city_name")));
				city.setCityCode(cursor.getString(cursor
						.getColumnIndex("city_code")));
				city.setProvinceId(provinceId);
				list.add(city);
			} while (cursor.moveToNext());
		}
		return list;
	}
}

public class ChooseAreaActivity extends BaseActivity {
	public static final int LEVEL_PROVINCE = 0;
	public static final int LEVEL_CITY = 1;
	private TextView titleText;
	private ListView listView;
	private ArrayAdapter<String> adapter;
	private CoolWeatherDB coolWeatherDB;
	private List<String> dataList = new ArrayList<String>();// 存放城市
	private SharedPreferences prefs;
	private AddCity addCity;// 添加的城市
	/**
	 * 省列表
	 */
	private List<Province> provinceList;
	/**
	 * 市列表
	 */
	private List<City> cityList;
	/**
	 * 选中的省份
	 */
	private Province selectedProvince;
	/**
	 * 当前选中的级别
	 */
	private int currentLevel;
	/**
	 * 是否从CityActivity中跳转过来。
	 */
	private boolean isFromCityActivity;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		isFromCityActivity = getIntent().getBooleanExtra("from_city_activity",
				false);
		prefs = PreferenceManager.getDefaultSharedPreferences(this);
		// 已经选择了城市且不是从CityActivity跳转过来，才会直接跳转到WeatherActivity，否则会一进来就又调到WeatherActivity
		if (prefs.getBoolean("city_selected", false) && !isFromCityActivity) {
			Intent intent = new Intent(this, WeatherActivity.class);
			startActivity(intent);
			finish();
			return;
		}
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(R.layout.choose_activity);
		listView = (ListView) findViewById(R.id.list_view);
		titleText = (TextView) findViewById(R.id.title_text);
		coolWeatherDB = CoolWeatherDB.getInstance(this);
		addCity = new AddCity();
		adapter = new ArrayAdapter<String>(this,
				android.R.layout.simple_list_item_1, dataList);
		listView.setAdapter(adapter);
		listView.setOnItemClickListener(new OnItemClickListener() {
			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				if (currentLevel == LEVEL_PROVINCE) {
					selectedProvince = provinceList.get(position);// 点0-北京-查询城市
					queryCities();
				} else if (currentLevel == LEVEL_CITY) {
					String cityName = cityList.get(position).getCityName();
					Intent intent = new Intent(ChooseAreaActivity.this,
							WeatherActivity.class);// 选择的城市名传递到WeatherActivity
					intent.putExtra("cityName", cityName);
					addCity.setCityName(cityName);
					coolWeatherDB.saveAddCity(addCity);// 保存到数据库
					System.out.println("ChooseAreaActivity" + cityName);
					startActivity(intent);
					finish();
				}
			}
		});
		queryProvinces(); // 默认加载省级数据
	}
	/**
	 * 从数据库查询查询全国所有的省
	 */
	private void queryProvinces() {
		provinceList = coolWeatherDB.loadProvinces();
		if (provinceList.size() > 0) {
			dataList.clear();// notifyDataSetChanged前先clear
			for (Province province : provinceList) {
				dataList.add(province.getProvinceName());
			}
			adapter.notifyDataSetChanged();
			listView.setSelection(0);
			titleText.setText("中国");
			currentLevel = LEVEL_PROVINCE;
		} else {
			Utility.json(this, coolWeatherDB);// 软件一进来先解析json（存放的城市信息）
			queryProvinces();
		}
	}
	/**
	 * 从数据库查询选中省内所有的市
	 */
	private void queryCities() {
		cityList = coolWeatherDB.loadCities(selectedProvince.getId() - 1);// 点0-北京-数据库里是1，所以-1
		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 {
			Utility.json(this, coolWeatherDB);
			queryCities();// 第一次进来开始解析json数据，插入数据库。第二进来直接从数据库获取
		}
	}
	/**
	 * 捕获Back按键，根据当前的级别来判断，此时应该返回市列表、省列表、还是直接退出。
	 */
	@Override
	public void onBackPressed() {
		if (currentLevel == LEVEL_CITY) {
			queryProvinces();
		} else {
			finish();
		}
	}
}