Android 입문 DatePickerDialog(순수 자바)

import java.util.Calendar;
import java.util.TimeZone;

import android.app.Activity;
import android.app.DatePickerDialog;
import android.app.DatePickerDialog.OnDateSetListener;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class DatePickerDialogTest extends Activity {
    
	private RelativeLayout mainView=null;
	private TextView tv=null;
	private Button button=null;
	private DatePickerDialog dpd=null;
	
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mainView=new RelativeLayout(this);
        tv=new TextView(this);
        RelativeLayout.LayoutParams lp_tv=new RelativeLayout.LayoutParams(-2,-2);
        lp_tv.addRule(RelativeLayout.CENTER_IN_PARENT);
        tv.setLayoutParams(lp_tv);
        tv.setText("     ");
        button=new Button(this);
        RelativeLayout.LayoutParams lp_button=new RelativeLayout.LayoutParams(-2,-2);
        lp_button.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
        lp_button.addRule(RelativeLayout.CENTER_HORIZONTAL);
        button.setLayoutParams(lp_button);
        button.setText("  ");
        button.setOnClickListener(new OnClickListener(){
			public void onClick(View v) {
				if(dpd==null){
					dpd_init();
				}
				dpd.show();
			}
        });
        mainView.addView(tv);
        mainView.addView(button);
        setContentView(mainView);
    }
    /*dpd   */
    void dpd_init(){
    	OnDateSetListener otsl=new OnDateSetListener(){
			public void onDateSet(DatePicker view, int year, int monthOfYear,int dayOfMonth) {
				tv.setText("      ："+year+" "+(monthOfYear+1)+" "+dayOfMonth+" ");
				dpd.dismiss();
			}
    	};
    	Calendar calendar=Calendar.getInstance(TimeZone.getDefault());
    	int year=calendar.get(Calendar.YEAR);
    	int month=calendar.get(Calendar.MONTH);
    	int day=calendar.get(Calendar.DAY_OF_MONTH);
    	dpd=new DatePickerDialog(this,otsl,year,month,day);
    }
}