Why it does not create the table and add data?

Question

DatabaseHelper.java:

import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String TAG = "DatabaseHelper";
    public static final String DATABASE_NAME = "daysDATABASE.db";
    public static final String TABLE_NAME = "daysDATABASE";
    private static final String COL1 = "datez";
    private static final String COL2 = "json";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + TABLE_NAME + " (id INTEGER PRIMARY KEY, datez TEXT, json TEXT)");
    }

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

    public boolean addData(String date, String json) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put("datez", date);
        contentValues.put("json", json);
        db.insert(TABLE_NAME, null, contentValues);
        return true;
    }

MainActivity.java:

public class MainActivity extends AppCompatActivity {
DatabaseHelper mydb;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_diary);

        mydb = new DatabaseHelper(this);
        mydb.addData("02164987", "adsdsadsadsadsadsadsa");
    }

If I open the database, there is no table in it, nor data ofc.. since the table is not created.

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I would tell more informations but I do not think you need more than this 2 java class. I copy pasted and changed some stuff from tutorialspoint tutorial but seems like it does not work for some reason.

Answer 1

Even if your table was created, you could not add data in it with the addData() method because you don't supply a value for the id column.
The CREATE statement creates the column id as PRIMARY KEY but not AUTOINCREMENT so you must supply its value. But I don't think that this is what you want.
So change the CREATE statement to this:

db.execSQL("CREATE TABLE " + TABLE_NAME + " (id INTEGER PRIMARY KEY AUTOINCREMENT, datez TEXT, json TEXT)");

then uninstall the app from the emulator/device so the db is deleted and run again.
This way the onCreate() method will be executed and the table will be created.
Edit1 : remember to close the database object after you're done with it:

mydb.close()

Edit2 : the insert() method, if successful, returns the id of the new added row or -1 if there was a problem, so I suggest you make this change in addData() method:

int id = db.insert(TABLE_NAME, null, contentValues); 
return (id >= 0);

Answer 2

Adding to forpas answer which solves the root cause of the problem, i will suggest you use

db.insertOrThrow(TABLE_NAME, null, contentValues);

instead of db.insert(TABLE_NAME, null, contentValues); so you can get a clue of what the problem might be.