DatePickerActivity.java

package com.materialdoc.ui.activity;

import android.app.Activity;
import android.app.DatePickerDialog;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.DatePicker;
import com.materialdoc.R;

import java.util.Calendar;

public class DatePickerActivity extends AppCompatActivity implements DatePickerDialog.OnDateSetListener {

    public static void start(@NonNull Activity activity) {
        Intent intent = new Intent(activity, DatePickerActivity.class);
        activity.startActivity(intent);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ac_date_picker);
        initViews();
    }

    @Override
    public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {

    }

    private void initViews() {
        findViewById(R.id.btnShow).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showDatePicker();
            }
        });

        findViewById(R.id.btnShowStyled).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showStyledDatePicker();
            }
        });
    }

    private void showDatePicker() {
        Calendar calendar = Calendar.getInstance();

        DatePickerDialog datePickerDialog = new DatePickerDialog(this, this,
                calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH),
                calendar.get(Calendar.DAY_OF_MONTH));

        datePickerDialog.show();
    }

    private void showStyledDatePicker() {
        Calendar calendar = Calendar.getInstance();

        DatePickerDialog datePickerDialog = new DatePickerDialog(this, R.style.DatePickerTheme, this,
                calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH),
                calendar.get(Calendar.DAY_OF_MONTH));

        datePickerDialog.show();
    }
}