Android Working with Button

Here, we are going to create two textfields and one button for sum of two numbers. If user clicks one the button, sum of two input values is displayed on the Toast.

Drag the component or write the code for UI in activity_main.xml

First of all, drag 2 textfields from the Text Fields palette and one button from the Form Widgets palette as shown in the following figure.

The generated code for the ui components will be like this:

File: activity_main.xml

<RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    tools:context=".MainActivity" >  
  
    <EditText  
        android:id="@+id/editText1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignParentTop="true"  
        android:layout_centerHorizontal="true"  
        android:layout_marginTop="24dp"  
        android:ems="10" />  
  
    <EditText  
        android:id="@+id/editText2"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignLeft="@+id/editText1"  
        android:layout_below="@+id/editText1"  
        android:layout_marginTop="34dp"  
        android:ems="10" >  
  
        <requestFocus />  
    </EditText>  
  
    <Button  
        android:id="@+id/button1"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_centerHorizontal="true"  
        android:layout_centerVertical="true"  
        android:text="@string/Button" />  
  
</RelativeLayout>  

Activity class

Now write the code to display the sum of two numbers.

File: MainActivity.java

package com.example.sumof2numbers;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity {
private EditText edittext1,edittext2;
private Button buttonSum;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addListenerOnButton();
}
public void addListenerOnButton(){
edittext1=(EditText)findViewById(R.id.editText1);
edittext2=(EditText)findViewById(R.id.editText2);
buttonSum=(Button)findViewById(R.id.button1);
buttonSum.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View view) {
String value1=edittext1.getText().toString();
String value2=edittext2.getText().toString();
int a=Integer.parseInt(value1);
int b=Integer.parseInt(value2);
int sum=a+b;
Toast.makeText(getApplicationContext(),String.valueOf(sum),Toast.LENGTH_LONG).show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}