Simple calculator program to add and subtract 2 numbers: Android tutorial

Program description:

This is a simple android calculator program with 3 edit text boxes, with 2 buttons.
User will enter two numbers in first and second edit text, and click the button.
button 1 is to add two numbers, and button 2 is to subtract the numbers.

             First Activity                         First Activity( after entering numbers)

          

             
     First Activity( click add)                                 First Activity( click sub)

           

First Activity

package com.example.b15_calc;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {
 //step1 : create all the variables.
 EditText et1, et2, et3;
 Button b1, b2;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  //step2 : get all the views from xml file.
  et1 = (EditText) findViewById(R.id.editText1);
  et2 = (EditText) findViewById(R.id.editText2);
  et3 = (EditText) findViewById(R.id.editText3);

  b1 = (Button) findViewById(R.id.button1);
  b2 = (Button) findViewById(R.id.button2);
  
  //step3 : write add functionality.
  b1.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    String f = et1.getText().toString();
    int i = Integer.parseInt(f);
    String s = et2.getText().toString();
    int j = Integer.parseInt(s);
    
    Integer result = i+j;
    String res = result.toString();
    et3.setText(res);
   }
  });
  b2.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    String f = et1.getText().toString();
    int i = Integer.parseInt(f);
    String s = et2.getText().toString();
    int j = Integer.parseInt(s);
    
    Integer result = i-j;
    String res = result.toString();
    et3.setText(res);
   }
  });
  
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  // Inflate the menu; this adds items to the action bar if it is present.
  getMenuInflater().inflate(R.menu.main, menu);
  return true;
 }

}

xml layout file for First Activity 

File name: activity_main.xml

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
   xmlns:tools="http://schemas.android.com/tools"  
   android:layout_width="match_parent"  
   android:layout_height="match_parent"  
   android:paddingBottom="@dimen/activity_vertical_margin"  
   android:paddingLeft="@dimen/activity_horizontal_margin"  
   android:paddingRight="@dimen/activity_horizontal_margin"  
   android:paddingTop="@dimen/activity_vertical_margin"  
   tools:context=".MainActivity" >  
   <EditText  
     android:id="@+id/editText1"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:layout_alignParentTop="true"  
     android:layout_centerHorizontal="true"  
     android:layout_marginTop="24dp"  
     android:ems="10"   
     android:inputType="textNoSuggestions"/>  
   <EditText  
     android:id="@+id/editText2"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:layout_alignLeft="@+id/editText1"  
     android:layout_below="@+id/editText1"  
     android:ems="10" />  
   <Button  
     android:id="@+id/button1"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:layout_alignLeft="@+id/editText2"  
     android:layout_below="@+id/editText2"  
     android:text="Add" />  
   <Button  
     android:id="@+id/button2"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:layout_alignBaseline="@+id/button1"  
     android:layout_alignBottom="@+id/button1"  
     android:layout_alignRight="@+id/editText2"  
     android:text="Sub" />  
   <EditText  
     android:id="@+id/editText3"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:layout_alignLeft="@+id/button1"  
     android:layout_below="@+id/button1"  
     android:ems="10" >  
     <requestFocus />  
   </EditText>  
 </RelativeLayout>  

Download complete code : Click to download

Similar basic activity programs:
How to start an activity and pass data to second screen. 
changing edittext text from button click listener 
How to start an activity from main activity on clicking button, and pass data 
Starting second activity based on login and password details 
Getting results from child activity

Tags : android calculator program, android tutorial, calculator