How to Create Simple Calculator using Android

Here in this article you will learn how to create a simple calculator application using Mono for Android The calculator will have the following functionality:

• Addition
• Subtraction
• Division
• Multiplication

Steps to create UI for Calculator

Steps to create Calculator in Android

-Create a new Mono for Android application named "Calculator".

Here is the  code of main.xml file.

<?xml version="1.0" encoding="utf-8"?>
 <AbsoluteLayout
 android:id="@+id/widget0"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:background="#808080ff"
 xmlns:android="http://schemas.android.com/apk/res/android"
 >
   <TextView
   android:id="@+id/Rlable"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:textColor="#ffffffff"
   android:text="Result"
   android:layout_x="11px"
   android:layout_y="37px"
 />
   <EditText
   android:id="@+id/Redittbox"
   android:layout_width="240px"
   android:layout_height="wrap_content"
   android:textSize="18sp"
   android:layout_x="70px"
   android:layout_y="28px"
 />
   <TextView
   android:id="@+id/Fvalue"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Enter First Value"
   android:layout_x="11px"
   android:layout_y="107px"
 />
   <TextView
   android:id="@+id/Svalue"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Enter Second Value"
   android:layout_x="12px"
   android:layout_y="155px"
 />
   <EditText
   android:id="@+id/FVeditbox"
   android:layout_width="67px"
   android:layout_height="wrap_content"
   android:textSize="18sp"
   android:layout_x="180px"
   android:layout_y="99px"
 />
   <EditText
   android:id="@+id/SVeditbox"
   android:layout_width="67px"
   android:layout_height="wrap_content"
   android:textSize="18sp"
   android:layout_x="179px"
   android:layout_y="146px"
 />
   <TextView
   android:id="@+id/OPlable"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Select the Operation"
   android:textSize="16sp"
   android:layout_x="77px"
   android:layout_y="216px"
 />
   <Button
   android:id="@+id/addition"
   android:layout_width="46px"
   android:layout_height="wrap_content"
   android:text="+"
   android:textSize="20sp"
   android:layout_x="18px"
   android:layout_y="266px"
 />
   <Button
   android:id="@+id/subtraction"
   android:layout_width="46px"
   android:layout_height="wrap_content"
   android:text="-"
   android:textSize="20sp"
   android:layout_x="91px"
   android:layout_y="266px"
 />
   <Button
   android:id="@+id/multiplication"
   android:layout_width="46px"
   android:layout_height="wrap_content"
   android:text="*"
   android:textSize="20sp"
   android:layout_x="167px"
   android:layout_y="266px"
 />
   <Button
   android:id="@+id/division"
   android:layout_width="46px"
   android:layout_height="wrap_content"
   android:text="/"
   android:textSize="20sp"
   android:layout_x="241px"
   android:layout_y="266px"
 />
   <TextView
   android:id="@+id/error"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
 />
 </AbsoluteLayout>

Now go to Activity1.cs file and inside the OnCreate() method we will creating and initialize all variables and create function for all theclick's.

Here is the code of Activity1.cs file.

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
namespace Calculator
{
    [Activity(Label ="Calculator", MainLauncher =true, Icon = "@drawable/icon")]

    public classActivity1 : Activity
    {
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            SetContentView(Resource.Layout.Main);

            Button btnadd = FindViewById<Button>(Resource.Id.addition);
            Button btnsub = FindViewById<Button>(Resource.Id.subtraction);
            Button btnmult = FindViewById<Button>(Resource.Id.multiplication);
            Button btndiv = FindViewById<Button>(Resource.Id.division);

            EditText firstvalue = FindViewById<EditText>(Resource.Id.FVeditbox);
            EditText secondvalue = FindViewById<EditText>(Resource.Id.SVeditbox);
            EditText result = FindViewById<EditText>(Resource.Id.Redittbox);

            TextView errormsg = FindViewById<TextView>(Resource.Id.error);

            double a, b, c;

            btnadd.Click += delegate
            {
                try
                {
                    a = double.Parse(firstvalue.Text);
                    b = double.Parse(secondvalue.Text);
                    c = a + b;
                    result.Text = c.ToString();
                }
                catch (Exception ex)
                {
                    errormsg.Text = ex.Message;
                }
            };

            btnsub.Click += delegate
            {
                try
                {
                    a = double.Parse(firstvalue.Text);
                    b = double.Parse(secondvalue.Text);
                    c = a - b;
                    result.Text = c.ToString();
                }
                catch (Exception ex)
                {
                    errormsg.Text = ex.Message;
                }
            };

            btnmult.Click += delegate
            {
                try
                {
                    a = double.Parse(firstvalue.Text);
                    b = double.Parse(secondvalue.Text);
                    c = a * b;
                    result.Text = c.ToString();
                }
                catch (Exception ex)
                {
                    errormsg.Text = ex.Message;
                }
            };

            btndiv.Click += delegate
            {
                try
                {
                    a = double.Parse(firstvalue.Text);
                    b = double.Parse(secondvalue.Text);
                    c = a / b;
                    result.Text = c.ToString();
                }
                catch (Exception ex)
                {
                    errormsg.Text = ex.Message;
                }
            };

        }
    }
}
 

Now Build and compile the application, the output looks like the below picture
out put: