How to build a simple Calculator app using Android Studio? in Java

 Practical no – 9 - Msbte diploma Semester 6

Greetings from "Its Easy Programming !! "

 

Today you will be learing to build your own Calculator using the Android Studio. Incase you feel its little tough for you , don't worry I have added the whole source code with XML and  JAVA file.

On our blog there are a variety of program codes for Android , C++, microprocessor8086, etc So do read them as well !!

XML code for calculator file.

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

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity">

    <EditText

        android:id="@+id/result_id"

        android:layout_width="fill_parent"

        android:layout_height="120dp"

        />

    <Button

        android:id="@+id/Btn7_id"

        android:layout_width="70dp"

        android:layout_height="60dp"

        android:layout_below="@id/result_id"

        android:text="7"

        android:onClick="btn7Clicked"

        />

    <Button

        android:id="@+id/Btn8_id"

        android:layout_width="70dp"

        android:layout_height="60dp"

        android:layout_below="@id/result_id"

        android:layout_toRightOf="@id/Btn7_id"

        android:text="8"

        android:onClick="btn8Clicked"

        />

    <Button

        android:id="@+id/Btn9_id"

        android:layout_width="70dp"

        android:layout_height="60dp"

        android:layout_below="@id/result_id"

        android:layout_toRightOf="@id/Btn8_id"

        android:text="9"

        android:onClick="btn9Clicked"

        />

    <Button

        android:id="@+id/Btnclear_id"

        android:layout_width="90dp"

        android:layout_height="60dp"

        android:layout_below="@id/result_id"

        android:layout_toRightOf="@id/Btn9_id"

        android:text="clear"

        android:onClick="btnclearClicked"

        />

    <Button

        android:id="@+id/Btn4_id"

        android:layout_width="70dp"

        android:layout_height="60dp"

        android:layout_below="@id/Btn7_id"

        android:text="4"

        android:onClick="btn4Clicked"

        />

 <Button

    android:id="@+id/Btn5_id"

    android:layout_width="70dp"

    android:layout_height="60dp"

    android:layout_below="@id/Btn8_id"

    android:layout_toRightOf="@id/Btn4_id"

    android:text="5"

    android:onClick="btn5Clicked"

    /> 

<Button

    android:id="@+id/Btn6_id"

    android:layout_width="70dp"

    android:layout_height="60dp"

    android:layout_below="@id/Btn9_id"

    android:layout_toRightOf="@id/Btn5_id"

    android:text="6"

    android:onClick="btn6Clicked"

    />

    <Button

        android:id="@+id/Btnplus_id"

        android:layout_width="90dp"

        android:layout_height="60dp"

        android:layout_below="@id/Btnclear_id"

        android:layout_toRightOf="@id/Btn6_id"

        android:text="+"

        android:onClick="btnplusClicked"

        />

    <Button

        android:id="@+id/Btn1_id"

        android:layout_width="70dp"

        android:layout_height="60dp"

        android:layout_below="@id/Btn4_id"

        android:text="1"

        android:onClick="btn1Clicked"

        /> <Button

    android:id="@+id/Btn2_id"

    android:layout_width="70dp"

    android:layout_height="60dp"

    android:layout_below="@id/Btn5_id"

    android:layout_toRightOf="@id/Btn1_id"

    android:text="2"

    android:onClick="btn2Clicked"

    />

 <Button

    android:id="@+id/Btn3_id"

    android:layout_width="70dp"

    android:layout_height="60dp"

    android:layout_below="@id/Btn6_id"

    android:layout_toRightOf="@id/Btn2_id"

    android:text="3"

    android:onClick="btn3Clicked"

    />

    <Button

        android:id="@+id/Btnminus_id"

        android:layout_width="90dp"

        android:layout_height="60dp"

        android:layout_below="@id/Btnplus_id"

        android:layout_toRightOf="@id/Btn3_id"

        android:text="-"

        android:onClick="btnminusClicked"

        />

    <Button

        android:id="@+id/Btnequal_id"

        android:layout_width="110dp"

        android:layout_height="60dp"

        android:layout_below="@id/Btn1_id"

        android:text="="

        android:onClick="btnequalClicked"

        />

    <Button

        android:id="@+id/Btndivide_id"

        android:layout_width="90dp"

        android:layout_height="60dp"

        android:layout_below="@id/Btn1_id"

        android:layout_toRightOf="@id/Btnequal_id"

        android:text="/"

        android:onClick="btndivideClicked"

        />

    <Button

        android:id="@+id/Btnmulti_id"

        android:layout_width="90dp"

        android:layout_height="60dp"

        android:layout_below="@id/Btnminus_id"

       android:layout_toRightOf="@id/Btndivide_id"

        android:text="*"

        android:onClick="btnmultiClicked"

       />

</RelativeLayout>

JAVA code for calculator

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import android.view.Menu;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

public class MainActivity extends AppCompatActivity {

    public String str ="";

    Character op = 'q';

    int i,num,numtemp;

    EditText showResult;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        showResult = (EditText)findViewById(R.id.result_id);

    }

    public void btn1Clicked(View v){

        insert(1);

    }

    public void btn2Clicked(View v){

        insert(2);

    }

    public void btn3Clicked(View v){

        insert(3);

    }

    public void btn4Clicked(View v){

        insert(4);

    }

    public void btn5Clicked(View v){

        insert(5);

    }

    public void btn6Clicked(View v){

        insert(6);

    }

    public void btn7Clicked(View v){

        insert(7);

    }

    public void btn8Clicked(View v){

        insert(8);

    }

    public void btn9Clicked(View v){

        insert(9);

    }

    public void btnplusClicked(View v){

        perform();

        op = '+';

    }

    public void btnminusClicked(View v){

        perform();

        op = '-';

    }

    public void btndivideClicked(View v){

        perform();

        op = '/';

    }

    public void btnmultiClicked(View v){

        perform();

        op = '*';

    }

    public void btnequalClicked(View v){

        calculate();

    }

    public void btnclearClicked(View v){

        reset();

    }

    private void reset() {

        // TODO Auto-generated method stub

        str ="";

        op ='q';

        num = 0;

        numtemp = 0;

        showResult.setText("");

    }

    private void insert(int j) {

        // TODO Auto-generated method stub

        str = str+Integer.toString(j);

        num = Integer.valueOf(str).intValue();

        showResult.setText(str);

    }

    private void perform() {

        // TODO Auto-generated method stub

        str = "";

        numtemp = num;

    }

    private void calculate() {

        // TODO Auto-generated method stub

        if(op == '+')

            num = numtemp+num;

        else if(op == '-')

            num = numtemp-num;

        else if(op == '/')

            num = numtemp/num;

        else if(op == '*')

            num = numtemp*num;

        showResult.setText(""+num);

   }}