Android DatePicker Spinners 不显示

Android DatePicker Spinners Not Displaying

我正在关注 Big Nerd Ranch Android 编程书籍。我目前正在尝试让 DatePicker 片段显示为微调器。它似乎不断显示日历视图,我不明白为什么。知道我做错了什么吗?

布局:

<?xml version="1.0" encoding="utf-8"?>
<DatePicker
    android:id="@+id/dialog_date_datePicker"
    android:spinnersShown="true"
    android:calendarViewShown="false"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

</DatePicker>

我是如何创建它的:

public class DatePickerFragment extends DialogFragment {
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        View v = getActivity().getLayoutInflater()
                .inflate(R.layout.dialog_date, null);

        return new AlertDialog.Builder(getActivity())
                .setView(v)
                .setTitle(R.string.date_picker_title)
                .setPositiveButton(android.R.string.ok, null)
                .create();
    }
}

尝试添加这个:

android:datePickerMode="spinner"

连同:

android:calendarViewShown="false"