Create Native Calculator Android Application

Introduction

Android is one of the most popular operating systems for mobile. In this article, I will show you how to create a Native Calculator Android application using Android Studio.

Requirements

Android Studio version 2.3.3
Little bit XML and JAVA knowledge.
Android Emulator (or) Android mobile
Download link (Android Studio)

Steps to be followed

The following steps are required to create a native Calculator Android application using Android Studio and I have included the source code below.

Step 1

Open Android Studio and start a new Android Studio Project.

Step 2

You can choose your application name and choose where your project is stored on the location. If you wish to use C++ for coding the project, mark the "Include C++ support", and click the "Next" button.

Now, select the version of Android and select the target Android devices.

Step 3

Now, add the activity and click the "Next" button.

Add Activity name and click the "Finish" button.

Step 4

Go to activity_main.xml, This XML file contains the designing code for an Android app in the activity_main.xml.

The XML code is given below.

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="20dp">
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="20dp">
<EditText
android:id="@+id/editText1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:inputType="numberDecimal"
android:textSize="20sp" />
<EditText
android:id="@+id/editText2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:inputType="numberDecimal"
android:textSize="20sp" />
</LinearLayout>
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="20dp">
<Button
android:id="@+id/Add"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="+"
android:textSize="30sp"/>
<Button
android:id="@+id/Sub"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="-"
android:textSize="30sp"/>
<Button
android:id="@+id/Mul"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="*"
android:textSize="30sp"/>
<Button
android:id="@+id/Div"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="/"
android:textSize="30sp"/>
</LinearLayout>
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="50dp"
android:text="The Answer is"
android:textSize="30sp"
android:gravity="center"/>
</LinearLayout>

Step 5

Go to Main Activity.java, This Java program is the back-end language for Android. Add the following code.

package com.example.hpworld.nativecalculator;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity implements OnClickListener
{
//Defining the Views
EditText Num1;
EditText Num2;
Button Add;
Button Sub;
Button Mul;
Button Div;
TextView Result;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Referring the Views
Num1 = (EditText) findViewById(R.id.editText1);
Num2 = (EditText) findViewById(R.id.editText2);
Add = (Button) findViewById(R.id.Add);
Sub = (Button) findViewById(R.id.Sub);
Mul = (Button) findViewById(R.id.Mul);
Div = (Button) findViewById(R.id.Div);
Result = (TextView) findViewById(R.id.textView);
// set a listener
Add.setOnClickListener(this);
Sub.setOnClickListener(this);
Mul.setOnClickListener(this);
Div.setOnClickListener(this);
}
@Override
public void onClick (View v)
{
float num1 = 0;
float num2 = 0;
float result = 0;
String oper = "";
// check if the fields are empty
if (TextUtils.isEmpty(Num1.getText().toString()) || TextUtils.isEmpty(Num2.getText().toString()))
return;
// read EditText and fill variables with numbers
num1 = Float.parseFloat(Num1.getText().toString());
num2 = Float.parseFloat(Num2.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
switch (v.getId())
{
case R.id.Add:
oper = "+";
result = num1 + num2;
break;
case R.id.Sub:
oper = "-";
result = num1 - num2;
break;
case R.id.Mul:
oper = "*";
result = num1 * num2;
break;
case R.id.Div:
oper = "/";
result = num1 / num2;
break;
default:
break;
}
// form the output line
Result.setText(num1 + " " + oper + " " + num2 + " = " + result);
}
}