Android DatePicker.

activity_main.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=".MainActivity" >

    <Button
        android:id="@+id/btnChangeDate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/cd" />

    <DatePicker
        android:id="@+id/dpResult"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_marginBottom="38dp" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/dpResult"
        android:layout_alignLeft="@+id/dpResult"
        android:layout_marginBottom="20dp"
        android:layout_marginLeft="20dp"
        android:text="@string/cd1" />

</RelativeLayout>

MainActivity.java

package com.mahi.datepicker;

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.DatePicker;

import android.widget.TextView;

public class MainActivity extends Activity {

DatePicker dp;

    Button b;

    TextView textview1;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

textview1=(TextView)findViewById(R.id.textView1);

        dp=(DatePicker)findViewById(R.id.dpResult);

        b=(Button)findViewById(R.id.btnChangeDate);

        

        textview1.setText(getCurrentDate());

        

        b.setOnClickListener(new OnClickListener(){

            @Override  

            public void onClick(View view) {

                textview1.setText(getCurrentDate());

            }

              

        });

}

public String getCurrentDate(){

        StringBuilder builder=new StringBuilder();

        builder.append("Current Date: ");

        builder.append((dp.getMonth() + 1)+"/");//month is 0 based

        builder.append(dp.getDayOfMonth()+"/");

        builder.append(dp.getYear());

        return builder.toString();

    }

@Override

public boolean onCreateOptionsMenu(Menu menu) {

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

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

return true;

}

}

Output: