Android DatePicker显示异常

《Android权威编程》里面的一道例题，
源代码
package com.bignerdranch.android.criminalintent;

import android.app.AlertDialog;
import android.app.Dialog;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.widget.DatePicker;

public class DatePickerFragment extends DialogFragment {
/*View v = getActivity().getLayoutInflater()
.inflate(R.layout.dialog_date, null);*/
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
DatePicker dp = new DatePicker(getActivity());
return new AlertDialog.Builder(getActivity())
.setView(dp)
.setTitle(R.string.date_picker_title)
.setPositiveButton(android.R.string.ok, null)
.create();
}
}
显示

代码看起来没有问题，你用手机试试，估计是模拟器才会出现的问题。