Create the graphical layout. Drag and drop three text fields (one each for the first number and the second number, and the last one to print the sum of the first two numbers), two TextView boxes to display text so that the user knows to enter two numbers, and finally a button for the addition action.

<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=".MainActivity" >

    <TextView>
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:text="First Number"
Text displayed to guide user to input first number
    </TextView>

    <EditText>
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:id="@+id/e1"
Variable e1 is declared to be referenced in java file.
        android:inputType="textPassword"
    </EditText>

    <TextView>
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Second Number"
    </TextView>

    <EditText>
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:id="@+id/e2"
        android:inputType="textPassword"
    </EditText>

    <Button>
        android:id="@+id/add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_marginBottom="122dp"
        android:text="Add"

    </Button>   
    <EditText>
        android:text=""
        android:id="@+id/t3" 

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textPassword"
    </EditText>
</RelativeLayout>

Now we have to write Java code to input and add the numbers, and output the sum. At this point, don't worry if you do not know Activity, Intent, and so on. Just focus on getting the code error-free. Eclipse guides you at each step. We start our program with MainActivity, coded like this:

package com.android.addition;
 
import android.os.Bundle;
import android.app.Activity;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Button;
import android.view.View;
 
public class MainActivity extends Activity {
    EditText e1;
    EditText e2;
    TextView t3;
    Button add;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        add=(Button)findViewById(R.id.action_settings);
        add.setOnClickListener(new Button.OnClickListener()
            {
        public void onClick
        (View v){Sum();}});
    }
        private void Sum(){
          int s1=Integer.parseInt(e1.getText().toString());
          int s2=Integer.parseInt(e2.getText().toString());
          int s3=s1+s2;
          t3.setText(Integer.toString(s3));
         }
}
 

See how straightforward this program is; it just takes two numbers, adds them together, and provides the result.

Debug and run the program. The emulator opens up and the program runs.