How To Create Calculator App For Android

Introduction

Ninety percent of people today use Android smartphones. In our day to day life, we perform mathematical operations with the help of a calculator. Thus, I will show you how to create a Calculator App for Android, using Android Studio. Android is the Kernel-based operating system. It allows the user, to modify GUI components and the source code.

Requirements

Android Studio.
Little bit XML and JAVA knowledge.

Download link (Android Studio): https://developer.android.com/studio/index.html.

Steps to be followed are given below

Carefully follow my steps to create a Calculator App for an Android and I have included the source code given below.

Step 1

Open an Android Studio. Start the new project.

Step 2

Put the Application name and company domain. If you wish to use C++ for coding the project, mark the Include C++ support, followed by clicking Next.

Step 3

Select the Android minimum SDK. Afterward, you chose the minimum SDK and it will show the approximate percentage of the people, who use SDK, followed by clicking Next.

Step 4

Choose the basic activity, followed by clicking Next.

Step 5

Put the activity name and layout name. Android Studio basically takes a Java class name, which is provided by you in the activity name

Step 6

Go to activity_calc.xml, followed by clicking the bottom text. This XML file contains the designing code for an Android app in the activity_calc.xml; copy and paste the code given below.

activity_calc.xml code

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/linearLayout1"
android:layout_marginLeft="10pt"
android:layout_marginRight="10pt"
android:layout_marginTop="3pt">
<EditText
android:layout_weight="1"
android:layout_height="wrap_content"
android:layout_marginRight="5pt"
android:id="@+id/etNum1"
android:layout_width="match_parent"
android:inputType="numberDecimal">
</EditText>
<EditText
android:layout_height="wrap_content"
android:layout_weight="1"
android:layout_marginLeft="5pt"
android:id="@+id/etNum2"
android:layout_width="match_parent"
android:inputType="numberDecimal">
</EditText>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/linearLayout2"
android:layout_marginTop="3pt"
android:layout_marginLeft="5pt"
android:layout_marginRight="5pt">
<Button
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:layout_weight="1"
android:text="+"
android:textSize="15pt"
android:id="@+id/btnAdd">
</Button>
<Button
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:layout_weight="1"
android:text="-"
android:textSize="15pt"
android:id="@+id/btnSub">
</Button>
<Button
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:layout_weight="1"
android:text="*"
android:textSize="15pt"
android:id="@+id/btnMult">
</Button>
<Button
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:layout_weight="1"
android:text="/"
android:textSize="15pt"
android:id="@+id/btnDiv">
</Button>
</LinearLayout>
<TextView
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:layout_marginLeft="5pt"
android:layout_marginRight="5pt"
android:textSize="12pt"
android:layout_marginTop="3pt"
android:id="@+id/tvResult"
android:gravity="center_horizontal">
</TextView>
</LinearLayout>

Step 8

In CalcActivity.java, copy and paste the code of Java programming given below, which is the backend language for an Android. Do not replace your package name, else an app will not run. The code given below contains my package name.

CalcActivity.java code

package ganeshannt.calc;
import android.app.Activity;
import android.os.Bundle;
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 CalcActivity extends Activity implements
OnClickListener
{
EditText input1;
EditText input2;
Button addition;
Button subtraction;
Button multiplication;
Button division;
TextView tvResult;
String oper = "";
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_calc);
input1 = (EditText) findViewById(R.id.etNum1);
input2 = (EditText) findViewById(R.id.etNum2);
addition = (Button) findViewById(R.id.btnAdd);
subtraction = (Button) findViewById(R.id.btnSub);
multiplication = (Button) findViewById(R.id.btnMult);
division = (Button) findViewById(R.id.btnDiv);
tvResult = (TextView) findViewById(R.id.tvResult);
// set a listener
addition.setOnClickListener(this);
subtraction.setOnClickListener(this);
multiplication.setOnClickListener(this);
division.setOnClickListener(this);
}
@Override
public void onClick(View v)
{
// TODO Auto-generated method stub
float num1 = 0;
float num2 = 0;
float result = 0;
// check if the fields are empty
if (TextUtils.isEmpty(input1.getText().toString())
|| TextUtils.isEmpty(input2.getText().toString()))
{
return;
}
// read EditText and fill variables with numbers
num1 = Float.parseFloat(input1.getText().toString());
num2 = Float.parseFloat(input2.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.btnAdd:
oper = "+";
result = num1 + num2;
break;
case R.id.btnSub:
oper = "-";
result = num1 - num2;
break;
case R.id.btnMult:
oper = "*";
result = num1 * num2;
break;
case R.id.btnDiv:
oper = "/";
result = num1 / num2;
break;
default:
break;
}
// form the output line
tvResult.setText(num1 + " " + oper + " " + num2 + " = " + result);
}
}