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;
}
}
};