Сложить числа из ListView

public class MainActivity extends Activity {
 
    ArrayList<Mylist> pr = new ArrayList<Mylist>();
    MyAdapter myAdapter;
    TextView tvResult;
    float summa = 0;
    private static final int delete = 1;
 
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        tvResult = (TextView) findViewById(R.id.sum);
 
        myAdapter = new MyAdapter(this, pr);
        for (float i = 1; i < pr.size(); i++) {
        }
 
        ListView lvMain = (ListView) findViewById(R.id.lvMain);
        lvMain.setAdapter(myAdapter);
        registerForContextMenu(lvMain);
 
    }
 
    public void showResult(View v) {
        Intent intent = new Intent(this, Main2Activity.class);
        startActivityForResult(intent, 1);
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (data == null) {
            return;
        }
        String name = data.getStringExtra("name");
        String name2 = data.getStringExtra("name2");
        float n1 = 0;
        float n2 = 0;
        float res = 0;
        n1 = Float.parseFloat(name);
        n2 = Float.parseFloat(name2);
        res = n1 * n2;
        summa += res;
        pr.add(new Mylist("Text ", res, R.mipmap.ic_launcher));
        myAdapter.notifyDataSetChanged();
        tvResult.setText("Итог " + summa + " м");
 
    }
 
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
                                    ContextMenu.ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        menu.add(0, delete, 0, "Удалить");
    }
 
    @Override
    public boolean onContextItemSelected(MenuItem item) {
        if (item.getItemId() == delete) {
            AdapterView.AdapterContextMenuInfo acmi = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
            Mylist result = (Mylist) myAdapter.getItem(acmi.position);
            summa -= result.price;
            pr.remove(acmi.position);
            myAdapter.notifyDataSetChanged();
            tvResult.setText("Итог " + summa + " м");
            return true;
        }
        return super.onContextItemSelected(item);
    }
 
}

public class MyAdapter extends BaseAdapter {
    Context ctx;
    LayoutInflater lInflater;
    ArrayList<Mylist> objects;
 
    MyAdapter(Context context, ArrayList<Mylist> obj) {
        ctx = context;
        objects = obj;
        lInflater = (LayoutInflater) ctx
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }
 
    @Override
    public int getCount() {
        return objects.size();
    }
 
    @Override
    public Object getItem(int position) {
        return objects.get(position);
    }
 
    @Override
    public long getItemId(int position) {
        return position;
    }
 
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = convertView;
        if (view == null) {
            view = lInflater.inflate(R.layout.item, parent, false);
        }
 
        Mylist p = getMylist(position);
 
        ((TextView) view.findViewById(R.id.tvName)).setText(p.name);
        ((TextView) view.findViewById(R.id.tvPrice)).setText(p.price + "");
        ((ImageView) view.findViewById(R.id.ivImage)).setImageResource(p.image);
 
        return view;
    }
 
    Mylist getMylist(int position) {
        return ((Mylist) getItem(position));
    }
}

public class Mylist {
 
    String name;
    float price;
    int image;
 
 
    Mylist(String _name, float _price, int _image) {
        name = _name;
        price = _price;
        image = _image;
    }
}