Notes

package com.example.arvind.calci;

import android.app.Activity;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


public class MainActivity extends Activity implements View.OnClickListener {

EditText etNum1;
EditText etNum2;
EditText etSym;

Button btnCal;

TextView tvResult;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

// find the elements
etNum1 = (EditText) findViewById(R.id.etNum1);
etNum2 = (EditText) findViewById(R.id.etNum2) ;
etSym = (EditText) findViewById(R.id.etSym);

btnCal = (Button) findViewById(R.id.btnCal);

tvResult = (TextView) findViewById(R.id.tvResult);

// set a listener
btnCal.setOnClickListener(this);

}

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
float num1 = 0;
float num2 = 0;
String str;
float result = 0;
// check if the fields are empty
if (TextUtils.isEmpty(etNum1.getText().toString())
|| TextUtils.isEmpty(etNum2.getText().toString())) {
return;
}

// read EditText and fill variables with numbers
num1 = Float.parseFloat(etNum1.getText().toString());
str = etSym.getText().toString();
num2 = Float.parseFloat(etNum2.getText().toString());


// defines the button that has been clicked and performs the corresponding operation
// write operation into oper, we will use it later for output
if(R.id.btnCal==R.id.btnCal){
switch(str)
{


case "+":
result = num1 + num2;
break;
case "-":
result = num1 - num2;
break;
case "*":
result = num1 * num2;
break;
case "/":
result = num1 / num2;
break;
default:
break;
}
}
// form the output line
tvResult.setText(num1 + " " + str + " " + num2 + " = " + result);
}
}