（一）、个人习惯写BD工具类

public class DBTools {

	private class DataOpenHelper extends sqliteOpenHelper {
		public DataOpenHelper(Context context) {
			super(context,"SYData.db",null,1);
		}

		@Override
		public void onCreate(sqliteDatabase db) {
			db.execsql("create table data(id integer primary key,json text)");
			db.execsql("insert into data values(?,?)",new String[] { "" + 1,"" });
			db.execsql("insert into data values(?,new String[] { "" + 2,"" });
		}

		@Override
		public void onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {

		}

	}

	/**
	 * 保存缓存
	 */
	public void saveJson(Context context,int id,String json) {
		DataOpenHelper helper = new DataOpenHelper(context);
		sqliteDatabase db = helper.getWritableDatabase();
		db.execsql("update data set json=? where id=?",new String[] { json,"" + id });
		db.close();
	}

	/**
	 * 读取缓存
	 */
	public String readJson(Context context,int id) {
		DataOpenHelper helper = new DataOpenHelper(context);
		sqliteDatabase db = helper.getWritableDatabase();
		Cursor cursor = db.rawQuery("select json from data where id = ?",new String[] { "" + id });
		boolean b = cursor.moveToFirst();
		if (b) {
			String json = cursor.getString(cursor.getColumnIndex("json"));
			return json;
		}
		db.close();
		return "";
	}

	
}

/**
	 * 缓存机制（即，从本地读取数据或网上下载数据）
	 */
	private void getDataOrUpdata() {
		// 读取本地缓存
		String result_hand = dbTools.readJson(getActivity(),1);
		String result_hot = dbTools.readJson(getActivity(),2);
		if (!result_hand.equals("") && !result_hot.equals("")) {
			dealJsonHeadData(result_hand);
			dealJsonHotData(result_hot);
			return;
		}
		// 网上下载数据
		if (isNetworkAble()) {
			getDataFromServer();
		}
	}

	// 判断网络是否连接是否可用
	private boolean isNetworkAble() {
		ConnectivityManager manager = (ConnectivityManager) getActivity()
				.getSystemService(Context.CONNECTIVITY_SERVICE);
		if (manager != null) {
			NetworkInfo info = manager.getActiveNetworkInfo();
			if (info != null && info.isAvailable()) {
				return true;
			}
		}
		return false;
	}