Example of using DatePicker and OnDateChangedListener()

<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="http://arteluzevida.blogspot.com/"
        android:textStyle="bold"
        android:layout_gravity="center_horizontal"
        android:autoLink="web" />
    
    <ScrollView 
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">
            
            <DatePicker 
                android:id="@+id/pickerdate"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"/>
            <TextView 
                android:id="@+id/info"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"/>
            
        </LinearLayout>
    </ScrollView>

</LinearLayout>

package com.example.androiddatepicker;

import java.util.Calendar;
import android.os.Bundle;
import android.app.Activity;
import android.widget.DatePicker;
import android.widget.DatePicker.OnDateChangedListener;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity{
 
 DatePicker pickerDate;
 TextView info;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  info = (TextView)findViewById(R.id.info);
  pickerDate = (DatePicker)findViewById(R.id.pickerdate);
  
  Calendar today = Calendar.getInstance();

  pickerDate.init(
    today.get(Calendar.YEAR), 
    today.get(Calendar.MONTH), 
    today.get(Calendar.DAY_OF_MONTH), 
    new OnDateChangedListener(){

     @Override
     public void onDateChanged(DatePicker view, 
       int year, int monthOfYear,int dayOfMonth) {
      Toast.makeText(getApplicationContext(), 
        "onDateChanged", Toast.LENGTH_SHORT).show();
      
      info.setText(
        "Year: " + year + "\n" +
        "Month of Year: " + monthOfYear + "\n" +
        "Day of Month: " + dayOfMonth);
      
     }});
  
 }

}

Download the files.

Next:
- Example of using TimePicker and OnTimeChangedListener()
- Options for DatePicker to display or hide calendar view and spinners