Calculator

[poxkix]

I can't get the equal button to work. Can anyone give some inputs why i'm doing wrong?

This is my code:

Button buttonPlus = (Button)findViewById(R.id.plus);
        buttonPlus.setOnClickListener(this.operator);
        Button buttonEqual = (Button)findViewById(R.id.equal);
        buttonEqual.setOnClickListener(this.operator);

protected OnClickListener operator = new OnClickListener() {
        public void onClick(View op) 
        {
            switch(op.getId()) {
            case R.id.plus:
                firstOperand = Integer.parseInt(output.getText().toString());
                operatr = R.string.button_17;
                output.setText("");                                
                break;
            case R.id.equal:
                if(operatr.equals("+")) {
                        secondOperand = Integer.parseInt(output.getText().toString());                
                        answer = firstOperand + secondOperand;
                        output.setText(answer + "");
                    }                                                        
                    break;
            }            
        }
    };