public void LvStairs(View view) {

        TextView lv = (TextView) findViewById(R.id.Lv_stairs);

        TableLayout table2 = (TableLayout) findViewById(R.id.table2);

        // values from activity
        EditText ta = (EditText) findViewById(R.id.Ta);
        String sTa = ta.getText().toString();
        double dTa = 0;
        try {
            dTa = Double.parseDouble(sTa);
        } catch (NumberFormatException e) {
            ta.setError("Вводите числа, пожалуйста");
        }

        EditText tr = (EditText) findViewById(R.id.Tr);
        String sTr = tr.getText().toString();
        double dTr = 0;
        try {
            dTr = Double.parseDouble(sTr);
        } catch (NumberFormatException e) {
            tr.setError("Вводите числа, пожалуйста");
        }

        double dTs = (dTa + dTr) / 2;
        double dps = 353 / dTs;
        double dpr = 353 / dTr;
        double dpa = 353 / dTa;

        //get a number of rows in TableLayout
        int gsn_count = table2.getChildCount();

        //initializing an TableRow here
        //there i've got an error
        TableRow gsnRow = (TableRow) table2.getChildAt(gsn_count);

        //getting a value from a child in row
        TextView tGsn = (TextView) gsnRow.getChildAt(2);

        String sGsn = tGsn.getText().toString();
        double dGsn = 0;
        try {
            dGsn = Double.parseDouble(sGsn);
        } catch (NumberFormatException e) {
            tGsn.setError("Ошибка");
        }

        double dLv = 3600 * dGsn / dpa;
        double dLvBD = new BigDecimal(dLv).setScale(0, RoundingMode.UP).doubleValue();
        String sLvBD = String.valueOf(dLvBD);

        //set value in a TextView
        lv.setText(sLvBD);
    }