Android在运行时从sqlite读取数据

我在联机时将所有数据存储在sqlite数据库中，然后在脱机时每次都尝试读取存储的数据库

 if(isOnline(getActivity()))

        {
            db = new DataBaseHandler(getActivity());
            getDataInAsyncTask();
            storeData(db);
            //db.close();
        }
        else
                    {

        Toast.makeText(getActivity(), "No internet",
                    Toast.LENGTH_LONG).show();

            try {
                db.openDataBase();
            } catch (SQLException sqle) {
                throw sqle;
            }
            getDataInDataBase(db);
            flag=0;
        }

在else条件下，即脱机模式下，我使用db.openDataBase（）在联机模式下打开/加载先前实现的数据库db

   public void openDataBase() throws SQLException{

        //Open the database
     String myPath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);}

db.openDataBase提供nullpointerException

---

我哪里做错了？加载/打开已构建的数据库db的方法正确吗

您从未初始化过db对象

排队

db=新的DataBaseHandler（getActivity（））

在if/else语句之前或try/catch语句内部

  /*
   * intitlize object globaly
  **/
   db = new DataBaseHandler(getActivity()); 
   if(isOnline(getActivity()))

    {
       /**
        *  look at these you are
        *  intialize object when is online
        */
        //db = new DataBaseHandler(getActivity()); 
        getDataInAsyncTask();
        storeData(db);
        //db.close();
    }
    else
                {

    Toast.makeText(getActivity(), "No internet",
                Toast.LENGTH_LONG).show();

        try {
            db.openDataBase();
        } catch (SQLException sqle) {
            throw sqle;
        }
        getDataInDataBase(db);
        flag=0;
    }