How To Make a Mini Calculator In Android

Introduction

In this article I will create a small application for a mini calculator. Whenever we want to just add, subtract, multiply, or divide two numbers, we usually want to use a mini calculator. So  I am telling you how to create  a mini calculator in Android. The following procedure shows how to create a mini calculator in Android.

Step 1

First of all create a new Android application project using: "File" -> "New"-> "Android Application Project" as shown below.

 

Step 2

Now open the "activity_main.xml" file and update it for the mini calculator UI screen as in the following code.

<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"

    tools:context=".MainActivity" >

    <EditText

        android:id="@+id/editText1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_alignParentRight="true"

        android:layout_alignParentTop="true"

        android:ems="10"

        android:maxLength="10"

        android:inputType="numberDecimal" />

    <EditText

        android:id="@+id/editText2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_alignParentRight="true"

        android:layout_below="@+id/editText1"

        android:ems="10"

        android:maxLength="10"

        android:inputType="numberDecimal" />

    <TextView

        android:id="@+id/textView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentBottom="true"

        android:layout_alignParentLeft="true"

        android:layout_alignParentRight="true"

        android:layout_below="@+id/button1"

        android:text="@string/result"

        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Button

        android:id="@+id/button4"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignBaseline="@+id/button3"

        android:layout_alignBottom="@+id/button3"

        android:layout_alignParentRight="true"

        android:text="@string/divdbtn" />

    <Button

        android:id="@+id/button3"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_above="@+id/textView1"

        android:layout_marginRight="16dp"

        android:layout_toLeftOf="@+id/button4"

        android:text="@string/multbtn" />

    <Button

        android:id="@+id/button2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_above="@+id/textView1"

        android:layout_marginRight="18dp"

        android:layout_toLeftOf="@+id/button3"

        android:text="@string/subbtn" />

    <Button

        android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_below="@+id/editText2"

        android:layout_marginRight="14dp"

        android:layout_toLeftOf="@+id/button2"

        android:text="@string/addbtn" />

</RelativeLayout>

Step 3

After updating the UI screen in "activity_main.xml"  update "strings.xml" witch stores all the strings. Update it as in the following code.

<?xml version="1.0" encoding="utf-8"?>

<resources>

    <string name="app_name">MiniClc</string>

    <string name="hello_world">Hello world!</string>

    <string name="menu_settings">Settings</string>

    <string name="result"></string>

    <string name="clc">Calculate</string>

    <string name="addbtn">Add</string>

    <string name="subbtn">Sub</string>

    <string name="multbtn">mult</string>

    <string name="divdbtn">divd</string>

</resources>

Step 4

Now open the "MainActivity.java" file from "src/com.mcn.minicalculator/MainActivity.java" and update it as in the following code.

package com.example.miniclc;

import android.app.Activity;

import android.os.Bundle;

import android.view.Menu;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

public class MainActivity extends Activity {

            double a,b,c;

            Button addbtn,subbtn,mulbtn,divdbtn;

      @Override

      protected void onCreate(Bundle savedInstanceState) {

            super.onCreate(savedInstanceState);

            setContentView(R.layout.activity_main);

            final EditText edt1=(EditText) findViewById(R.id.editText1);

            final EditText edt2=(EditText) findViewById(R.id.editText2);

            final TextView result= (TextView) findViewById(R.id.textView1);

             addbtn=(Button) findViewById(R.id.button1);

             subbtn=(Button) findViewById(R.id.button2);

             mulbtn=(Button) findViewById(R.id.button3);

             divdbtn=(Button) findViewById(R.id.button4);

            addbtn.setOnClickListener(new Button.OnClickListener()

            {public void onClick

                  (View  v) { calculate();}

            private void calculate() {

                  // TODO Auto-generated method stub

                    a=Double.parseDouble(edt1.getText().toString());

                  b=Double.parseDouble(edt2.getText().toString());

                  c=a+b;

                  result.setText(Double.toString(c));

            }});

            subbtn.setOnClickListener(new Button.OnClickListener()

            {public void onClick

                  (View  v) { calculate();}

            private void calculate() {

                  // TODO Auto-generated method stub

                    a=Double.parseDouble(edt1.getText().toString());

                  b=Double.parseDouble(edt2.getText().toString());

                  c=a-b;

                  result.setText(Double.toString(c));

            }});

            mulbtn.setOnClickListener(new Button.OnClickListener()

            {public void onClick

                  (View  v) { calculate();}

            private void calculate() {

                  // TODO Auto-generated method stub

                    a=Double.parseDouble(edt1.getText().toString());

                  b=Double.parseDouble(edt2.getText().toString());

                  c=a*b;

                  result.setText(Double.toString(c));

            }});

            divdbtn.setOnClickListener(new Button.OnClickListener()

            {public void onClick

                  (View  v) { calculate();}

            private void calculate() {

                  // TODO Auto-generated method stub

                    a=Double.parseDouble(edt1.getText().toString());

                  b=Double.parseDouble(edt2.getText().toString());

                  c=a/b;

                  result.setText(Double.toString(c));

            }});

      }

      @Override

      public boolean onCreateOptionsMenu(Menu menu) {

            // Inflate the menu; this adds items to the action bar if it is present.

            getMenuInflater().inflate(R.menu.activity_main, menu);

            return true;

      }

}

 

Output

The output will show on the current screen where you enter the query.

If you click on the "Add" button then you will get the addition of both numbers.

And if you click on "Sub" then the result will be the subtraction.

And if you click on "mult" then you will get the multiplication.

And after clicking on "divd" you will get the division.