The retrieving of data from sqlite database is done through this code

Question

I am not getting the add string returned back. The android app takes input as food item and prints its respective calories. here is the code for creating table:

public class dietclass extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "diet7.db";
    public static final String TABLE_NAME = "Cal_val";
    public static final String COL1 = "ID";
    public static final String COL2 = "ITEM";
    public static final String COL3 = "QUANTITY";
    public static final String COL4 = "CALORIES";
    public dietclass(Context context) {
        super(context,DATABASE_NAME,null,1);
        SQLiteDatabase db = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
       db.execSQL("create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT,ITEM TEXT,QUANTITY VARCHAR,CALORIES INTEGER)");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
       db.execSQL("DROP TABLE IF EXISTS " +TABLE_NAME);
        onCreate(db);
    }
}

And here is the code for retrieving data from my activity which is taking item and calories as input.

public class foodcal extends AppCompatActivity {
    EditText item;
    EditText quantity;
    TextView calories;
    Button calculate;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_foodcal);
        item = (EditText)findViewById(R.id.etitem);
        quantity = (EditText)findViewById(R.id.etquantity);
        calories = (TextView)findViewById(R.id.calories);
        calculate = (Button)findViewById(R.id.calculate);
        calculate.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                String itemstr = item.getText().toString();
                printDatabase(itemstr);
                //String dbstring = dietclass.databaseToString(itemstr);
                //calories.setText(String.valueOf(dbstring));
            }
    });
    }

    public void printDatabase(String item){
        String dbstring = dietclass.databaseToString(this,item);
        //String label;
        //label = dbstring + "calories";
        calories.setText(String.valueOf(dbstring));
  }

    private static class dietclass extends SQLiteOpenHelper {
        private static String DB_PATH = "/data/data/com.example.janhvik.dietapp/databases/";
        private static String DB_NAME = "diet7.db";
        private static String TABLE_NAME = "Cal_val";
        private static SQLiteDatabase myDataBase;
        private Context myContext;

        public dietclass(Context context) {
            super(context, DB_NAME, null, 1);
            this.myContext = context;
        }
    private static String databaseToString(Context ctx, String item_name) {
            String myDbPath;
            int cal = 0 ;
            String add="";
            myDbPath = DB_PATH+DB_NAME;
            myDataBase = SQLiteDatabase.openOrCreateDatabase(myDbPath, null);
            String query = "SELECT * FROM "+TABLE_NAME+" WHERE ITEM='"+item_name+"'";
            Cursor c = myDataBase.rawQuery(query,null);

            if(c!= null && c.moveToFirst()){
                add = c.getString(c.getColumnIndex("CALORIES"));
                c.close();
            }
            add = add + " calories";
            //Toast.makeText(ctx,add, Toast.LENGTH_LONG).show();
            return add;
            }

I am not getting any error but the code is not taking the value from the select query, can anyone help in this.

yes i tried it, my output is returning the empty string(add) and i think select query is not working. — Sophia, Dec 16 '17 at 11:39
does your toast works when you are trying to display the calories ? — Lokesh Pandey, Dec 16 '17 at 11:46
@janhvi try to replace `myDataBase = SQLiteDatabase.openOrCreateDatabase(myDbPath, null);` with `myDataBase = getWritableDatabase();` — Om Infowave Developers, Dec 16 '17 at 11:52
@Lokesh No, the toast doesn't work.It remains blank, even empty toast doesn't appear. — Sophia, Dec 16 '17 at 11:52
@janhvi It's a good time for you to learn debugging start using try and catch block to see where your code breaks — Lokesh Pandey, Dec 16 '17 at 11:53
By reading your code seems fine and I can not debug your code right now. You may be missing some thing — Lokesh Pandey, Dec 16 '17 at 11:55
Thanks @Lokesh , debugging has to be done here. Because i am also not able to catch the error. — Sophia, Dec 16 '17 at 12:05
@OmInfowaveDevelopers i tried to do getWritableDatabase() but it is showing error, i also tries for getReadableDatabase(), no errors but the same problem is faced. — Sophia, Dec 16 '17 at 12:07
also, CALORIES is an integer and you are getting `c.getString` — Om Infowave Developers, Dec 16 '17 at 12:10
@OmInfowaveDevelopers I tried using `c.getInt()` too but the data is not retrieved. — Sophia, Dec 16 '17 at 12:20
have you checked there is data in a database? try to print c.count() for a check there is data in db.or try https://stackoverflow.com/questions/9997976/android-pulling-sqlite-database-android-device — Om Infowave Developers, Dec 16 '17 at 12:25

score 0 · Accepted Answer · answered Dec 17 '17 at 04:27

I think you've got rather mixed up and complicated matters by appearing to use multiple database helpers/methods to open the same database when you only need to use the database helper. I'm unsure what the exact issue was, there was insufficient code to build an exact replica.

Instead a created simplified working code.

Here's a rewrite/simplification based upon your code :-

First ONE databasehelper class namely dietclass :-

public class dietclass extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "diet7.db";
    public static final String TABLE_NAME = "Cal_val";
    public static final String COL1 = "ID";
    public static final String COL2 = "ITEM";
    public static final String COL3 = "QUANTITY";
    public static final String COL4 = "CALORIES";
    //private static String DB_PATH = "/data/data/com.example.janhvik.dietapp/databases/";
    //private static String DB_NAME = "diet7.db";
    SQLiteDatabase myDataBase;


    private Context myContext;

    public dietclass(Context context) {
        super(context,DATABASE_NAME,null,1);
        myDataBase = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT,ITEM TEXT,QUANTITY VARCHAR,CALORIES INTEGER)");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " +TABLE_NAME);
        onCreate(db);
    }

    public long insertCal_ValEntry(String item, String quantity, int calories) {
        ContentValues cv = new ContentValues();
        cv.put(COL2,item);
        cv.put(COL3,quantity);
        cv.put(COL4,calories);
        return myDataBase.insert(TABLE_NAME,null,cv);
    }


    public String databaseToString(String item_name) {

        //String myDbPath;
        int cal = 0 ;
        String add="";
        //myDbPath = DB_PATH+DB_NAME;
        //myDataBase = SQLiteDatabase.openOrCreateDatabase(myDbPath, null);

        String query = "SELECT * FROM "+TABLE_NAME+" WHERE ITEM='"+item_name+"'";
        Cursor c = myDataBase.rawQuery(query,null);

        if(c.moveToFirst()){
            add = c.getString(c.getColumnIndex("CALORIES"));
            c.close();
        }
        add = add + " calories";
        //Toast.makeText(ctx,add, Toast.LENGTH_LONG).show();
        return add;
    }
}

Notes

For testing purposes, method insertCal_ValEntry has been added.
Done away with any attempt to open Database rather this is done by the helper.
The check to see if the cursor is null has been removed, it is basically useless as SQLite will not return a null, it will always return a cursor, which may be empty. the Cursor move??? methods, such as moveToFirst return false if the move cannot be made.
Context isn't required by the databaseToString method so removed it.
databaseToString method made to be an instance method rather than class method (i.e not static) and made it public.

The activity in this case I've used MainActivity

public class MainActivity extends AppCompatActivity {

    EditText item;
    EditText quantity;
    TextView calories;
    Button calculate;

    dietclass dbhelper; //<<<< we want an instance of the database helper
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_foodcal);

        item = (EditText)findViewById(R.id.etitem);
        quantity = (EditText)findViewById(R.id.etquantity);
        calories = (TextView)findViewById(R.id.calories);
        calculate = (Button)findViewById(R.id.calculate);

        dbhelper = new dietclass(this); //<<<< get the instance of the database helper

        dbhelper.insertCal_ValEntry("Porridge", "100g",5000); //<<<< For testing 
        dbhelper.insertCal_ValEntry("Cake","500g", 20000); //<<<< For testing


        calculate.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                String itemstr = item.getText().toString();
                printDatabase(itemstr);

                //String dbstring = dietclass.databaseToString(itemstr);
                //calories.setText(String.valueOf(dbstring));
            }
        });
    }

    public void printDatabase(String item){
        String dbstring =  dbhelper.databaseToString(item); //<<<< 
        //String label;wr
        //label = dbstring + "calories";
        calories.setText(String.valueOf(dbstring));
    }
}

Notes

The principle used above could be used in any activity. That is get an instance of the database helper and then invoked methods within the helper to get/add/alter data in the database.

Results from the above:-

1) When App is started:-

2) Clicking without input (or inputting item not in table) :-

3) Clicking after inputting valid item :-

Additional Info

If you really want to get the database path the following is less prone to errors:-

    String databasepath = getDatabasePath(dietclass.DATABASE_NAME).getPath();
    ((TextView) findViewById(R.id.dbpath)).setText(databasepath);

With the dbpath TextView (note run on 7.0.0 device):-

On a 4.1.1 device :-

Thanks for it, i got the problem and it is working. I added the data in the table externally and it wasn't accessed by the android. — Sophia, Dec 17 '17 at 06:29

The retrieving of data from sqlite database is done through this code

1 Answers1

First ONE databasehelper class namely dietclass :-

Notes

The activity in this case I've used MainActivity

Notes

Results from the above:-

Additional Info