Android - Error เมื่อกดปุ่มแล้วโชว์ DatePicker Popup ใน Fragment

package com.example.trainning;

import java.util.Calendar;

import android.app.DatePickerDialog;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.app.Dialog;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;

public class View2Activity extends Fragment{
private Button test;
Calendar myCalendar = Calendar.getInstance();
DatePickerDialog.OnDateSetListener Mydate = new DatePickerDialog.OnDateSetListener() {
	
	@Override
	public void onDateSet(DatePicker view, int year, int monthOfYear,
			int dayOfMonth) {
		myCalendar.set(Calendar.YEAR, year);
        myCalendar.set(Calendar.MONTH, monthOfYear);
        myCalendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);		
	}
};
 public View2Activity() {
     }
	   public View onCreateView(LayoutInflater inflater, ViewGroup container,
               Bundle savedInstanceState) {
           View rootView = inflater.inflate(R.layout.activity_view2, 
        		   container, false);
           test = (Button)getView().findViewById(R.id.testDate);
           test.setOnClickListener(new View.OnClickListener() {
   			
   			@Override
   			public void onClick(View v) {
   				// TODO Auto-generated method stub
   				new DatePickerDialog(getActivity(),
   						Mydate,
   						myCalendar.get(Calendar.YEAR),
   						myCalendar.get(Calendar.MONTH),
   						myCalendar.get(Calendar.DAY_OF_MONTH)).show();
   			}   
              });         
           return rootView;
       }

}