Basic Calculator

In this tutorial, I will show you how to create simple calculator in Android. See output below!

Here's the CalculatorModel.java

package com.example.calculator;

public class CalculatorModel {

double m_num1, m_num2;

//constructor

public CalculatorModel(double num1, double num2){
this.m_num1 = num1;
this.m_num2 = num2;
}

//setters

public void setNum1(double num1){
this.m_num1 = num1;
}

public void setNum2(double num2){
this.m_num2 = num2;
}

//getters

public double getNum1(){
return this.m_num1;
}

public double getNum2(){
return this.m_num2;
}

}

Here's the CalculatorController.java

package com.example.calculator;

public class CalculatorController {

public double addition(CalculatorModel cmodel){

return cmodel.m_num1 + cmodel.m_num2;

}

public double subtraction(CalculatorModel cmodel){

return cmodel.m_num1 - cmodel.m_num2;

}

public double multiplication(CalculatorModel cmodel){

return cmodel.m_num1 * cmodel.m_num2;

}

public double divistion(CalculatorModel cmodel){

return cmodel.m_num1 / cmodel.m_num2;

}

}

Here's the CalculatorActivity.java

package com.example.calculator;

import android.app.Activity;

import android.os.Bundle;

import android.view.Menu;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

public class CalculatorActivity extends Activity implements OnClickListener{

EditText et_result;

Button btn_one, btn_two, btn_three, btn_four, btn_five, btn_six, btn_seven, 

btn_eight, btn_nine, btn_zero, btn_point, btn_add, btn_minus, btn_times, 

btn_divide, btn_equal, btn_clear;

double num1 = 0;

int indicator = 0;

CalculatorModel c_model;

CalculatorController c_controller;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_calculator);

initializeVars();

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

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

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

return true;

}

public void initializeVars(){

et_result = (EditText)findViewById(R.id.et_result);

btn_one = (Button)findViewById(R.id.btn_one);

btn_two = (Button)findViewById(R.id.btn_two);

btn_three = (Button)findViewById(R.id.btn_three);

btn_four = (Button)findViewById(R.id.btn_four);

btn_five = (Button)findViewById(R.id.btn_five);

btn_six = (Button)findViewById(R.id.btn_six);

btn_seven = (Button)findViewById(R.id.btn_seven);

btn_eight = (Button)findViewById(R.id.btn_eight);

btn_nine = (Button)findViewById(R.id.btn_nine);

btn_zero = (Button)findViewById(R.id.btn_zero);

btn_point = (Button)findViewById(R.id.btn_point);

btn_add = (Button)findViewById(R.id.btn_add);

btn_minus = (Button)findViewById(R.id.btn_minus);

btn_times = (Button)findViewById(R.id.btn_times);

btn_divide = (Button)findViewById(R.id.btn_divide);

btn_equal = (Button)findViewById(R.id.btn_equal);

btn_clear = (Button)findViewById(R.id.btn_clear);

btn_one.setOnClickListener(this);

btn_two.setOnClickListener(this);

btn_three.setOnClickListener(this);

btn_four.setOnClickListener(this);

btn_five.setOnClickListener(this);

btn_six.setOnClickListener(this);

btn_seven.setOnClickListener(this);

btn_eight.setOnClickListener(this);

btn_nine.setOnClickListener(this);

btn_zero.setOnClickListener(this);

btn_point.setOnClickListener(this);

btn_add.setOnClickListener(this);

btn_minus.setOnClickListener(this);

btn_times.setOnClickListener(this);

btn_divide.setOnClickListener(this);

btn_equal.setOnClickListener(this);

btn_clear.setOnClickListener(this);

}

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

try{

switch(v.getId()){

case R.id.btn_one:

et_result.setText(et_result.getText().toString()+btn_one.getText().toString());

break;

case R.id.btn_two:

et_result.setText(et_result.getText().toString()+btn_two.getText().toString());

break;

case R.id.btn_three:

et_result.setText(et_result.getText().toString()+btn_three.getText().toString());

break;

case R.id.btn_four:

et_result.setText(et_result.getText().toString()+btn_four.getText().toString());

break;

case R.id.btn_five:

et_result.setText(et_result.getText().toString()+btn_five.getText().toString());

break;

case R.id.btn_six:

et_result.setText(et_result.getText().toString()+btn_six.getText().toString());

break;

case R.id.btn_seven:

et_result.setText(et_result.getText().toString()+btn_seven.getText().toString());

break;

case R.id.btn_eight:

et_result.setText(et_result.getText().toString()+btn_eight.getText().toString());

break;

case R.id.btn_nine:

et_result.setText(et_result.getText().toString()+btn_nine.getText().toString());

break;

case R.id.btn_zero:

et_result.setText(et_result.getText().toString()+btn_zero.getText().toString());

break;

case R.id.btn_point:

et_result.setText(et_result.getText().toString()+btn_point.getText().toString());

break;

case R.id.btn_add:

num1 = Double.parseDouble(et_result.getText().toString());

et_result.setText("");

indicator = 1;

break;

case R.id.btn_minus:

num1 = Double.parseDouble(et_result.getText().toString());

et_result.setText("");

indicator = 2;

break;

case R.id.btn_times:

num1 = Double.parseDouble(et_result.getText().toString());

et_result.setText("");

indicator = 3;

break;

case R.id.btn_divide:

num1 = Double.parseDouble(et_result.getText().toString());

et_result.setText("");

indicator = 4;

break;

case R.id.btn_clear:

et_result.setText("");

break;

case R.id.btn_equal:

c_model = new CalculatorModel(num1, Double.parseDouble(et_result.getText().toString()));

c_controller = new CalculatorController();

switch(indicator){

case 1:

et_result.setText(Double.toString(c_controller.addition(c_model)));

break;

case 2:

et_result.setText(Double.toString(c_controller.subtraction(c_model)));

break;

case 3:

et_result.setText(Double.toString(c_controller.multiplication(c_model)));

break;

case 4:

et_result.setText(Double.toString(c_controller.divistion(c_model)));

break;

}

break;

}

}catch(Exception e){

e.printStackTrace();

}

}

}

And lastly, the activity_calculator.xml

<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"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".CalculatorActivity" >

    <RelativeLayout 

        android:id="@+id/rl_hold_calculator"

        android:layout_width="250dp"

        android:layout_height="wrap_content"

        android:layout_centerHorizontal="true"

        android:layout_centerVertical="true">

        "

   <EditText

       android:id="@+id/et_result"

       android:layout_width="fill_parent"

       android:layout_height="wrap_content"

       android:layout_marginTop="20dp"

       android:ems="10"

       android:inputType="numberDecimal" >

       <requestFocus />

   </EditText>

   <Button

       android:id="@+id/btn_one"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignLeft="@+id/et_result"

       android:layout_below="@+id/et_result"

       android:layout_marginTop="10dp"

       android:text="1" />

   <Button

       android:id="@+id/btn_two"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_one"

       android:layout_alignBottom="@+id/btn_one"

       android:layout_toRightOf="@+id/btn_one"

       android:text="2" />

   <Button

       android:id="@+id/btn_three"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_two"

       android:layout_alignBottom="@+id/btn_two"

       android:layout_toRightOf="@+id/btn_two"

       android:text="3" />

   <Button

       android:id="@+id/btn_four"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_three"

       android:layout_alignBottom="@+id/btn_three"

       android:layout_toRightOf="@+id/btn_three"

       android:text="4" />

   <Button

       android:id="@+id/btn_five"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignLeft="@+id/btn_one"

       android:layout_below="@+id/btn_one"

       android:layout_marginTop="10dp"

       android:text="5" />

   <Button

       android:id="@+id/btn_six"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_five"

       android:layout_alignBottom="@+id/btn_five"

       android:layout_alignLeft="@+id/btn_two"

       android:text="6" />

   <Button

       android:id="@+id/btn_seven"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_six"

       android:layout_alignBottom="@+id/btn_six"

       android:layout_alignLeft="@+id/btn_three"

       android:text="7" />

   <Button

       android:id="@+id/btn_eight"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_seven"

       android:layout_alignBottom="@+id/btn_seven"

       android:layout_toRightOf="@+id/btn_seven"

       android:text="8" />

    

    

   <Button

       android:id="@+id/btn_nine"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignLeft="@+id/btn_five"

       android:layout_below="@+id/btn_five"

       android:layout_marginTop="10dp"

       android:text="9" />

   <Button

       android:id="@+id/btn_zero"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_nine"

       android:layout_alignBottom="@+id/btn_nine"

       android:layout_toRightOf="@+id/btn_nine"

       android:text="0" />

   <Button

       android:id="@+id/btn_point"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_zero"

       android:layout_alignBottom="@+id/btn_zero"

       android:layout_toRightOf="@+id/btn_zero"

       android:text="." />

   <Button

       android:id="@+id/btn_clear"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_point"

       android:layout_alignBottom="@+id/btn_point"

       android:layout_toRightOf="@+id/btn_point"

       android:text="C" />

   <Button

       android:id="@+id/btn_add"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignLeft="@+id/btn_nine"

       android:layout_below="@+id/btn_nine"

       android:layout_marginTop="10dp"

       android:text="+" />

   <Button

       android:id="@+id/btn_minus"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_add"

       android:layout_alignBottom="@+id/btn_add"

       android:layout_toRightOf="@+id/btn_add"

       android:text="-" />

   <Button

       android:id="@+id/btn_times"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_minus"

       android:layout_alignBottom="@+id/btn_minus"

       android:layout_alignLeft="@+id/btn_point"

       android:text="*" />

   <Button

       android:id="@+id/btn_divide"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignBaseline="@+id/btn_times"

       android:layout_alignBottom="@+id/btn_times"

       android:layout_alignLeft="@+id/btn_clear"

       android:text="/" />

   <Button

       android:id="@+id/btn_equal"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       android:layout_alignLeft="@+id/btn_add"

       android:layout_alignParentRight="true"

       android:layout_below="@+id/btn_add"

       android:layout_marginTop="10dp"

       android:text="=" />

    

    </RelativeLayout>

</RelativeLayout>

That's it, hope this simple tutorial may help you. Happy Coding!