下午好，我是Android Studio开发新手，我正在开发一个应用程序，需要在其中一个Fragments中创建日历。
我试图在我的片段中创建一个CalendarView，但是setContentView方法和其他方法都以红色突出显示，我做错了什么？

public class CalendarFragment extends Fragment  {
    private CalendarView calendarView;

    public CalendarFragment() {
        // Required empty public constructor
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_calendar);
        CalendarView calendarView = findViewById(R.id.calendarView);
        calendarView.setOnDateChangeListener(new OnDateChangeListener() {

            @Override
            public void onSelectedDayChange(CalendarView view, int year,
                                            int month, int dayOfMonth) {
                int mYear = year;
                int mMonth = month;
                int mDay = dayOfMonth;
                String selectedDate = new StringBuilder().append(mMonth + 1)
                        .append("-").append(mDay).append("-").append(mYear)
                        .append(" ").toString();
                Toast.makeText(getApplicationContext(), selectedDate, Toast.LENGTH_LONG).show();
            }
        });
    }
}