从多维数组获取值太慢

Question

Good Day, I've been working on an update in an android project, and came across an issue. I have to read questions from an SQLite database which i've done successfully by loading it into a multi-dimensional array as shown below in my database helper class:

public String getSome(int s,int t, String Table_Name){

        String selectQuery = "SELECT  * FROM " + Table_Name;
              SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        int rows = cursor.getCount();
        int num=0;
        int col = 0;
        String[][] base = new String[rows][13]; 

        if (cursor.moveToFirst()) {
            do {
                for (col=0;col<13;++col ){
                base[num][col] = (cursor.getString(col));} 
                ++num;
            } while (cursor.moveToNext());

            return base[s][t];
        }



        return null;

    }

With that done, i read the questions as such in my question class:

public void database_calls(){
          setCourseTag(courseTag);
          myDbHelper = new DataBaseHelper(getActivity());


            try {
                myDbHelper.createDataBase();
            } catch (IOException ioe) {
            throw new Error("Unable to create database");
            }

            try {
                myDbHelper.openDataBase();
            }catch(SQLException sqle){
                throw sqle;
            }

            String no= myDbHelper.getSome(ques,0, getCourseTag());
            String qu = myDbHelper.getSome(ques,1, getCourseTag());
            String a = myDbHelper.getSome(ques,2, getCourseTag());
            String b = myDbHelper.getSome(ques,3, getCourseTag());
            String c = myDbHelper.getSome(ques,4, getCourseTag());
            String d = myDbHelper.getSome(ques,5, getCourseTag());
            ans = myDbHelper.getSome(ques,6, getCourseTag());
            img = Integer.parseInt(myDbHelper.getSome(ques,8, getCourseTag()));
            exp = myDbHelper.getSome(ques,9, getCourseTag());
            year = myDbHelper.getSome(ques,10, getCourseTag());
            questionImage = myDbHelper.getSome(ques,11, getCourseTag());
            length = myDbHelper.getMax(getCourseTag());
        }

So recently, i tried to use the year column, (ie, column 10) to qualify the questions chosen for each quiz session, so that the user may be able to select the questions from any year, he/she wants to attempt. In order to do this, i used a loop at the beginning of the activity to filter out only the required year past questions. Then i transferred the indices of each question to a set, bal , from where it is iterated and so on..

public void countYearQuestions(){

        for(int y = 0; y < length; ++y){
            //year = myDbHelper.getSome(y,10, getCourseTag()); 

            if (selectedYear.equals(myDbHelper.getSome(y,10, getCourseTag())))
              bal.add(y);
        }
    }

Here, length is the size of the entire question database, for the course, (indicated by getCourseTag()). The code works quite alright. But it takes a whole 8-9secs!! for the activity to load. Any help on how to reduce this loading time would be appreciated.

Answer 1

The way you're doing this is pretty efficient in slowing everything down (and your helper helps you with it a lot):

String no= myDbHelper.getSome(ques,0, getCourseTag());

In each such line you execute a query, create a 2D array holding the whole table and throw nearly everything away. And you fail to close the Cursor .

So you need 12 values from a table and read instead the whole table 12 times.