Android | App to Add Two Numbers

Difficulty Level : Basic
Last Updated : 15 Apr, 2019

Below are the steps for Creating a Simple Android Application to Add Two Numbers

STEP-1: First of all go to the xml file
STEP-2: Now go to the text and write the code for adding 3 textview,2 textedit and Button and Assign ID to each component. Assign margin top, left, right for the location.
STEP-3: Now, open up the activity java file.
STEP-4: Declare few variables and the values entered in the Text Views can be read by using an id which we have set in the XML code above.
STEP-5: Add the click listener to the Add button.
STEP-6: When the Add button has been clicked, add the values and store it into the sum variable.
STEP-7: To show the output in the result text view, set the sum in the textview.

Complete code of layout xml file and java file is given below.

activity_main.xml

<!--The activity_main.xml is a layout file
 an XML-based layout is a file that defines
 the different widgets to be used in the UI
 and the relations between those widgets
 and their containers. -->
  
  
<?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"
    tools:layout_editor_absoluteY="81dp">
  
    <!-- Text view for result view-->
    <TextView
        android:id="@+id/textView_answer"
        android:layout_width="100dp"
        android:layout_height="25dp"
        android:layout_marginLeft="130dp"
        android:layout_marginTop="300dp"
        android:text="0"
        android:textSize="20dp"
        android:textStyle="bold" />
  
    <!--take the input first number-->
    <EditText
        android:id="@+id/editText_first_no"
        android:layout_width="150dp"
        android:layout_height="40dp"
        android:layout_marginLeft="200dp"
        android:layout_marginTop="40dp"
        android:inputType="number" />
    <!-- for messege input first number-->
    <TextView
        android:id="@+id/textView_first_no"
        android:layout_width="150dp"
        android:layout_height="25dp"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="50dp"
        android:text="First number"
        android:textSize="20dp" />
  
    <!--view messege -->
    <TextView
        android:id="@+id/textView_second_no"
        android:layout_width="150dp"
        android:layout_height="25dp"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="100dp"
        android:text="Second number"
        android:textSize="20dp" />
  
    <!-- take input for second number -->
  
    <EditText
        android:id="@+id/editText_second_no"
        android:layout_width="150dp"
        android:layout_height="40dp"
        android:layout_marginLeft="200dp"
        android:layout_marginTop="90dp"
        android:inputType="number"
        tools:ignore="MissingConstraints" />
  
    <!-- button for run add logic and view result -->
  
    <Button
        android:id="@+id/add_button"
        android:layout_width="100dp"
        android:layout_height="50dp"
        android:layout_marginLeft="110dp"
        android:layout_marginTop="200dp"
        android:text="ADD" />
  
</RelativeLayout>

MainActivity.java

// Each new activity has its own layout and Java files, 
// here we build the logic for adding two number 
  
package org.geeksforgeeks.addtwonumbers;
  
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
  
public class MainActivity extends AppCompatActivity {
  
    // define the global variable
  
    // variable number1, number2 for input input number
    // Add_button, result textView
  
    EditText number1;
    EditText number2;
    Button Add_button;
    TextView result;
    int ans=0;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
  
        // by ID we can use each component which id is assign in xml file
        number1=(EditText) findViewById(R.id.editText_first_no);
        number2=(EditText) findViewById(R.id.editText_second_no);
        Add_button=(Button) findViewById(R.id.add_button);
        result = (TextView) findViewById(R.id.textView_answer);
  
        // Add_button add clicklistener
        Add_button.setOnClickListener(new View.OnClickListener() {
  
            public void onClick(View v) {
  
                // num1 or num2 double type
                // get data which is in edittext, convert it to string
                // using parse Double convert it to Double type
                double num1 = Double.parseDouble(number1.getText().toString());
                double num2 = Double.parseDouble(number2.getText().toString());
                // add both number and store it to sum
                double sum = num1 + num2;
                // set it ot result textview
                result.setText(Double.toString(sum));
            }
        });
    }
}