数据不会从数据库中删除

Question

First of all I have to tell I am still learning Android studio and maybe I missed some important and obvious staff.

Now I am facing with problem with my database, or maybe RecycleViwe i am not sure.

I my app, I am trying insert data into db and only in case if data is empty. I did it and I think that works. Now I am trying to implement new method to read data and delete. For now I can show data in my recycleView.

My problem come with delete method. When I start app, and when delete some items it is show like everything is fine. But when I start app again, data appears again like nothing was happened. 

I am not sure what cause this problem. Hope some of you guys can help me?

Below you will find parts of code. If you want to see more, feel free to ask me.

In this part of code, I call my data and showing them in recycleView.

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

        pondeljak = (Button) findViewById(R.id.buttonPonedeljak);
        utorak = (Button) findViewById(R.id.buttonUtorak);
        sreda = (Button) findViewById(R.id.buttonSreda);
        cetvrtak = (Button) findViewById(R.id.buttonCetvrtak);
        petak = (Button) findViewById(R.id.buttonPetak);




        View view  = getLayoutInflater().inflate(R.layout.casovi,null);

        alertDialogBuilder = new AlertDialog.Builder(this);
        alertDialogBuilder.setView(view);

        db = new DataDays(this);

        alertDialog = alertDialogBuilder.create();

        recyclerView = (RecyclerView) view.findViewById(R.id.recycleCasoviID);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        casoviList = new ArrayList<>();
        casoviItems = new ArrayList<>();

       casoviList = db.getCasoviPonedeljak();

        for (Casovi c: casoviList){

            Casovi casovi = new Casovi();

            casovi.setRedniBrCasa(c.getRedniBrCasa());
            casovi.setNzaivCasa(c.getNzaivCasa());

            casoviItems.add(casovi);
        }

        recycleViewAdapter = new RecycleViewAdapter(this, casoviItems);
        recyclerView.setAdapter(recycleViewAdapter);
        recycleViewAdapter.notifyDataSetChanged();


        pondeljak.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (db.casoviCountPondeljak() == 0){
                    Intent intent = new Intent(MainActivity.this, Unos_casova.class);
                    intent.putExtra("Dan", "Pondeljak");
                    startActivity(intent);

                }else {
                    alertDialog.show();

                }
            }
        });

Here is my recycleView and there is also my deletemethod. For sure core fore delete method could be written in a more simple way but I copied some of my last trials.

public class RecycleViewAdapter extends RecyclerView.Adapter<RecycleViewAdapter.ViewHolder> {

    private Context context;
    private List<Casovi> casoviItems;

    public RecycleViewAdapter(Context context, List<Casovi> casoviItems) {
        this.context = context;
        this.casoviItems = casoviItems;
    }


    @Override
    public RecycleViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.prikaz_casova, parent,false);
        return new ViewHolder(view, context);
    }

    @Override
    public void onBindViewHolder( RecycleViewAdapter.ViewHolder holder, int position) {

        Casovi casovi = casoviItems.get(position);


        holder.redniBrCasPrikaz.setText(casovi.getRedniBrCasa());
        holder.nazivCasPrikaz.setText(casovi.getNzaivCasa());

    }

    @Override
    public int getItemCount() {

        return casoviItems.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        public TextView redniBrCasPrikaz;
        public TextView nazivCasPrikaz;
        public Button delteBtn;
        public Button editBtn;
        public CardView cardView;
        public int id;


        public ViewHolder(View view, Context ctx) {
            super(view);

            context = ctx;


            redniBrCasPrikaz = (TextView) view.findViewById(R.id.rednibrojCasaID);
            nazivCasPrikaz = (TextView) view.findViewById(R.id.nazivcasaID);
            delteBtn = (Button) view.findViewById(R.id.obrisiCasBtnID);
            editBtn = (Button) view.findViewById(R.id.izmeniCasBtnID);
            cardView = (CardView) view.findViewById(R.id.carViewID);

            delteBtn.setOnClickListener(this);
            editBtn.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {

            switch (view.getId()){
                case R.id.obrisiCasBtnID:

                    int position = getAdapterPosition();
                    Casovi casovi = casoviItems.get(position);
                    deleteItem(casovi.getId());
                    notifyItemRemoved(getAdapterPosition());
                    break;
            }

        }

        public void deleteItem (final int id){

            DataDays db = new DataDays(context);
            db.deleteCas(id);
            casoviItems.remove(getAdapterPosition());
        }
    }
}

And here are some parts of Data Base. As I told you I am not sure what can be a problem, maybe some of these method are written in a wrong way.

    public void addCasovePonedeljak (Casovi casovi){

        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();

        values.put(Constants.DAN, "Ponedeljak");
        values.put(Constants.REDNI_CAS, casovi.getRedniBrCasa());
        values.put(Constants.CAS, casovi.getNzaivCasa());

        db.insert(Constants.TABLE_NAME, null, values);


    }


    public List<Casovi> getCasoviPonedeljak(){

        SQLiteDatabase db = this.getReadableDatabase();
        List<Casovi> casoviList = new ArrayList<>();

       String pondeljakQuery = "SELECT * FROM " + Constants.TABLE_NAME + " WHERE " + Constants.DAN + " = " + " 'Ponedeljak' ";

       Cursor cursor = db.rawQuery(pondeljakQuery, null);

        if (cursor.moveToFirst()){
            do {

                Casovi casovi = new Casovi();

                //casovi.setId(Integer.parseInt(cursor.getString(cursor.getColumnIndex(Constants.ID))));
                //casovi.setDan(cursor.getString(cursor.getColumnIndex(Constants.DAN)));
                casovi.setNzaivCasa(cursor.getString(cursor.getColumnIndex(Constants.CAS)));
                casovi.setRedniBrCasa(cursor.getString(cursor.getColumnIndex(Constants.REDNI_CAS)));

                casoviList.add(casovi);

            }while (cursor.moveToNext());

        }

        return casoviList;

        }




    public void deleteCas(int id){

        SQLiteDatabase db = this.getWritableDatabase();

        db.delete(Constants.TABLE_NAME, Constants.CAS + " = ?",
                new String[] {});

        db.close();
    }



    public int casoviCountPondeljak() {

        String countQuery = "SELECT * FROM " + Constants.TABLE_NAME;
        //String countQuery = "SELECT COUNT(*) FROM " + Constants.TABLE_NAME + " WHERE " + Constants.DAN + " = '" + "Ponedeljak' ";

        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.rawQuery(countQuery,null);
        //cursor.moveToFirst();
        return cursor.getCount();


    }
}

Answer 1

Your delete method is wrong.. You are passing parameter id but not using the id in your method as

public void deleteCas(int id){

    SQLiteDatabase db = this.getWritableDatabase();

    db.delete(Constants.TABLE_NAME, Constants.CAS + " = ?",
            new String[] {});

    db.close();
}

It should be

public void deleteCas(int id){

    SQLiteDatabase db = this.getWritableDatabase();

    db.delete(Constants.TABLE_NAME, Constants.CAS + " = ?",
            new String[] {id.toString()});

    db.close();
}

Syntax not tested