How to Create a Simple Calculator in Android

Monday 7 December 2020

How to Create a Simple Calculator in Android

December 07, 2020 Android , Education 0 Comments

 In this tutorial, we are going to create a simple calculator in android by using android studio. This calculator has a very beautiful interface and user-friendly coding. First, you need to create a new project using android studio, then you need to give a specific name to your project. for example My Calculator. As you are given in the screenshots. 



Now you need to design the layout out your calculator by using the  XML language. XML coding is given below;

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    android:padding="10dp"
    tools:context=".MainActivity">
    <EditText
        android:id="@+id/edit_screen"
        android:layout_width="match_parent"
        android:layout_height="110dp"
        android:textSize="20sp"
        android:padding="10dp"
        android:textAlignment="viewEnd"
        android:gravity="center"
        android:cursorVisible="false"
        android:paddingVertical="35dp"
        tools:ignore="RtlCompat">

    </EditText>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="25dp"
       android:paddingTop="1dp"
        >


        <Button
            android:id="@+id/btn_one"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="1"
            android:textSize="20sp"></Button>

        <Button
            android:id="@+id/btn_two"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="2"
            android:textSize="20sp"></Button>
        <Button
            android:id="@+id/btn_three"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="3"
            android:textSize="20sp"></Button>
        <Button
            android:id="@+id/btn_clear"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:textColor="@android:color/holo_red_light"
            android:textAllCaps="false"
            android:text="Clear"
            android:textSize="20sp"></Button>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="1dp"
        android:paddingTop="1dp"
        >


        <Button
            android:id="@+id/btn_four"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="4"
            android:textSize="20sp"></Button>

        <Button
            android:id="@+id/btn_five"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="5"
            android:textSize="20sp"></Button>
        <Button
            android:id="@+id/btn_six"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="6"
            android:textSize="20sp"></Button>
        <Button
            android:id="@+id/btn_power"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="@string/power"
            android:textSize="20sp"></Button>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="1dp"
        android:paddingTop="1dp"
        >


        <Button
            android:id="@+id/btn_seven"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="7"
            android:textSize="20sp"></Button>

        <Button
            android:id="@+id/btn_eight"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="8"
            android:textSize="20sp"></Button>
        <Button
            android:id="@+id/btn_nine"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="9"
            android:textSize="20sp"></Button>
        <Button
            android:id="@+id/btn_minus"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="-"
            android:textSize="20sp"></Button>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="1dp"
        android:paddingTop="1dp"
        >


        <Button
            android:id="@+id/btn_plus"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="+"
            android:textSize="20sp"></Button>

        <Button
            android:id="@+id/btn_zero"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="0"
            android:textSize="20sp"></Button>

        <Button
            android:id="@+id/btn_dot"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:background="@drawable/buttons"
            android:gravity="center"
            android:layout_margin="3dp"
            android:text="."
            android:textSize="20sp"></Button>
        <Button
            android:id="@+id/btn_divide"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:background="@drawable/buttons"
            android:gravity="center"
            android:layout_margin="3dp"
            android:text="/"
            android:textSize="20sp"></Button>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="1dp"
        android:paddingTop="1dp"
        >


        <Button
            android:id="@+id/btn_multiply"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/buttons"
            android:layout_margin="3dp"
            android:text="X"
            android:textSize="20sp"></Button>

        <Button
            android:id="@+id/btn_equal"
            android:layout_width="wrap_content"
            android:layout_height="73dp"
            android:layout_weight="1"
            android:gravity="center"
            android:background="@drawable/equal_button"
            android:layout_margin="3dp"
            android:text= "="
            android:textSize="20sp"></Button>
    </LinearLayout>

</LinearLayout>


Here you are seen that android:background="@drawable/buttons" and android:background="@drawable/equal_button" in the XML code. I have made two drawable resource files with the name of  buttons and equal_button, creating these two you need to right on drawables and then follow the screenshots.



The code of  these two file are;


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<?xml version="1.0" encoding="utf-8"?>
<selector  xmlns:android="http://schemas.android.com/apk/res/android"
    >
    <item>
        <shape android:shape="rectangle">
            <corners android:radius="10dp"></corners>
           <solid android:color="#CFCACA"></solid>
        </shape>

    </item>

</selector>



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<?xml version="1.0" encoding="utf-8"?>
<selector  xmlns:android="http://schemas.android.com/apk/res/android"
    >
    <item>
        <shape android:shape="rectangle">
            <corners android:radius="10dp"></corners>
            <solid android:color="#31D152"></solid>
        </shape>

    </item>

</selector>


Java Coding: 

Now we are going to start java coding. This calculator performs the five mathematical operations like Addition, Subtraction, Multiplication, Division and Power of any number. Here is the java code;






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package com.example.mycalculator;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
private Button btnOne,btnTwo,btnThree,btnFour,btnFive,btnSix,btnSeven,btnEight,btnNine,btnZero,btnPlus,btnMinus,btnMultiply,
         btnDivide,btnEqual,btnClear,btnDot,btnPower;
private EditText editScreen;
private float firstNumber ,secondNumber,result;
private char operation;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnOne = findViewById(R.id.btn_one);
        btnTwo = findViewById(R.id.btn_two);
        btnThree = findViewById(R.id.btn_three);
        btnFour = findViewById(R.id.btn_four);
        btnFive = findViewById(R.id.btn_five);
        btnSix = findViewById(R.id.btn_six);
        btnSeven = findViewById(R.id.btn_seven);
        btnEight = findViewById(R.id.btn_eight);
        btnNine = findViewById(R.id.btn_nine);
        btnZero = findViewById(R.id.btn_zero);
        btnMinus = findViewById(R.id.btn_minus);
        btnMultiply = findViewById(R.id.btn_multiply);
        btnPlus = findViewById(R.id.btn_plus);
        btnDivide = findViewById(R.id.btn_divide);
        btnEqual = findViewById(R.id.btn_equal);
        btnDot = findViewById(R.id.btn_dot);
        btnClear = findViewById(R.id.btn_clear);
        btnPower = findViewById(R.id.btn_power);
        editScreen = findViewById(R.id.edit_screen);

        btnClear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText("");
                firstNumber = (float) 0.0;
                secondNumber = (float) 0.0;
            }
        });

        btnOne.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnOne.getText().toString());
            }
        });

        btnTwo.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnTwo.getText().toString());
            }
        });

        btnThree.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnThree.getText().toString());
            }
        });

        btnFour.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnFour.getText().toString());
            }
        });

        btnFive.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnFive.getText().toString());
            }
        });

        btnSix.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnSix.getText().toString());
            }
        });

        btnSeven.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnSeven.getText().toString());
            }
        });

        btnEight.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnEight.getText().toString());
            }
        });

        btnNine.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnNine.getText().toString());
            }
        });

        btnZero.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText() + btnZero.getText().toString());
            }
        });

        btnPlus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(editScreen.getText().toString().isEmpty())
                {
                    Toast.makeText(MainActivity.this, "Please! first write something...", Toast.LENGTH_SHORT).show();
                }
                else
                {
                   firstNumber = Float.parseFloat( editScreen.getText().toString());
                    editScreen.setText("");
                    operation = '+';
                }
            }
        });

        btnMultiply.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(editScreen.getText().toString().isEmpty())
                {
                    Toast.makeText(MainActivity.this, "Please! first write something...", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    firstNumber = Float.parseFloat( editScreen.getText().toString());
                    editScreen.setText("");
                    operation = 'x';
                }
            }
        });

        btnMinus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(editScreen.getText().toString().isEmpty())
                {
                    Toast.makeText(MainActivity.this, "Please! first write something...", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    firstNumber = Float.parseFloat( editScreen.getText().toString());
                    editScreen.setText("");
                    operation = '-';
                }
            }
        });

        btnDivide.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(editScreen.getText().toString().isEmpty())
                {
                    Toast.makeText(MainActivity.this, "Please! first write something...", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    firstNumber = Float.parseFloat( editScreen.getText().toString());
                    editScreen.setText("");
                    operation = '/';
                }
            }
        });

        btnDot.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                editScreen.setText(editScreen.getText().toString() + btnDot.getText().toString());
            }
        });
        btnPower.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(editScreen.getText().toString().isEmpty())
                {
                    Toast.makeText(MainActivity.this, "Please! first write any number...", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    firstNumber = Float.parseFloat( editScreen.getText().toString());
                    result = firstNumber * firstNumber;
                    editScreen.setText(String.valueOf(result));
                }
            }
        });

        btnEqual.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                if (editScreen.getText().toString().isEmpty())
                {
                    Toast.makeText(MainActivity.this, "Please first write something...", Toast.LENGTH_SHORT).show();
                }
                else
                    {
                    secondNumber = Float.parseFloat( editScreen.getText().toString());
                    switch (operation)
                    {
                        case '+':
                        {
                           addition(firstNumber,secondNumber);
                           break;
                        }
                        case '-':
                        {
                            substraction(firstNumber,secondNumber);
                            break;
                        }
                        case '/':
                        {
                            division(firstNumber,secondNumber);
                            break;
                        }
                        case 'x':
                        {
                           multiplication(firstNumber,secondNumber);
                            break;
                        }
                    }
                    editScreen.setText(String.valueOf(result));
                   }

            }
        });


    }

    private float substraction(float fNumber, float sNumber)
    {
        result = fNumber - sNumber;
        return result;
    }

    private float addition(float fNumber, float sNumber)
    {
        result = fNumber + sNumber;
        return result;
    }
    private float multiplication(float fNumber, float sNumber)
    {
        result = fNumber * sNumber;
        return result;
    }
    private float division(float fNumber, float sNumber)
    {
        result = fNumber / sNumber;
        return result;
    }
}

Now run the app through emulator or android device.

Output: Here are the screenshots of our Calculator

Making Android Calculator using android studio

I hope you liked it.

#AndroidDevelopment
#CalculatorInAndroid
#AndroidStudio
#Android
#Howwhy
#HowWhy308

Thanks





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