Vfrdtyky

I'm a beginner in android Studio, I am following a tutorial with code like this

public class dbhelper extends SQLiteOpenHelper {





public static final string DATABASE_NAME = "perpustakaan.db";

public static final string TABLE_NAME = "user";

public static final string DATABASE_VERSION = 1;

public static final string COL_1 = "username";

public static final string COL_2 = "password";



    public dbhelper(Context context) {

    super(context, DATABASE_NAME, null, 1);

}

On the line super the android studio said it was an error, while I saw the tutorial it didn't call an error. I'm using the Android Studio ver 3.2.1

1. You have mismatched braces (last one is missing)


2. string should be String (upper case S).


3. You cannot assign a numeric value to a String DATABASE_VERSION needs to be an int (lowercase).
   
   
   
   
   • int is a primitive type (as are short, long, char, byte, boolean, float, double) and are lower case, String is a Class and by convention starts with an Uppercase (Pascal case),
   
   
   • if you were to follow such Conventions instead of dbhelper you would use DBHelper rather than dbhelper.
   
   
   
   


4. You need to add two overidden methods for onCreate and onUpgrade as these are required.

So the above at a minimum needs to be something like :-

public class dbhelper extends SQLiteOpenHelper {





    public static final String DATABASE_NAME = "perpustakaan.db";

    public static final String TABLE_NAME = "user";

    public static final int DATABASE_VERSION = 1;

    public static final String COL_1 = "username";

    public static final String COL_2 = "password";



    public dbhelper(Context context) {

        super(context, DATABASE_NAME, null, DATABASE_VERSION);

    }



    @Override

    public void onCreate(SQLiteDatabase db) {



    }



    @Override

    public void onUpgrade(SQLiteDatabase db, int i, int i1) {



    }

}

• Note that DATABASE_VERSION has been used for the database version (otherwsie it is useless).

In the onCreate method you would typically define the table(s) that are to be in the database.

Perhaps the onCreate method could be :-

@Override

public void onCreate(SQLiteDatabase db) {

    String crt_sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" +

            COL_1 + " TEXT UNIQUE," +

            COL_2 + " TEXT" +

            ")";

    db.execSQL(crt_sql);

}

Thus, when the onCreate method is called the user table would be created.

• The onCreate method is called once only for the lifetime of the database.


• The onCreate method is not called when you instantiate the dbhelper class (e.g. by using dbhelper mydatabase = new dbhelper(this); but when an attempt is made to accesss the database)