为什么片段没有在导航抽屉中打开？

Question

我的 MainActivity.java 包含

navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        switch (item.getItemId())
        {
            case R.id.calendar:
                fragmentTransaction = getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.main_container,  new Calender());
                fragmentTransaction.commit();
                getSupportActionBar().setTitle("Calender");
                item.setChecked(true);
                break;
           // drawer.closeDrawers();
        }
        return true;
    }
});

我的 Calender.java 包含

public class Calender extends android.support.v4.app.Fragment{
    Activity a;
    CalendarView calendar;
    public Calender() {
        // Required empty public constructor
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState)  {
        // Inflate the layout for this fragment
        a = new Activity();
        a.setContentView(R.layout.fragment_calender);

        initializeCalendar();
        return inflater.inflate(R.layout.fragment_calender, container, false);

    }

    public void initializeCalendar() {

        calendar = (CalendarView) a.findViewById(R.id.calendar);
        // sets whether to show the week number.
        calendar.setShowWeekNumber(false);
        // sets the first day of week according to Calendar.
        // here we set Monday as the first day of the Calendar
        calendar.setFirstDayOfWeek(2);
        //The background color for the selected week.
        calendar.setSelectedWeekBackgroundColor(getResources().getColor(R.color.green));
        //sets the color for the dates of an unfocused month.
        calendar.setUnfocusedMonthDateColor(getResources().getColor(R.color.transparent));
        //sets the color for the separator line between weeks.
        calendar.setWeekSeparatorLineColor(getResources().getColor(R.color.transparent));
        //sets the color for the vertical bar shown at the beginning and at the end of the selected date.
        calendar.setSelectedDateVerticalBar(R.color.darkgreen);
        //sets the listener to be notified upon selected date change.
        calendar.setOnDateChangeListener(new OnDateChangeListener() {
            @Override
            public void onSelectedDayChange(CalendarView view, int year, int month, int day) {
                Toast.makeText(a.getApplicationContext(), day + "/" + month + "/" + year, Toast.LENGTH_LONG).show();
            }
        });

    }
}

我的片段有问题吗？ 还是在主要活动中？ 请尽快帮助。应用程序打开但我尝试单击日历按钮的地方，没有显示任何内容。

Answer 1

为什么你的片段中有一个活动实例？ 将您的 onCreateView 更改为：

public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    View view = inflater.inflate(R.layout.content_main, parent, false);
    calendar = (CalendarView) view.findViewById(R.id.calendar);
    return view;
}

然后在 onViewCreated 方法中执行以下操作：

initializeCalendar();

确保 content_main 中日历视图的 ID 是日历。

Answer 2

如果使用Navigation Architecture Component ，则不必手动将片段连接到抽屉MenuItem。 The system will automatically tie you MenuItem to specific fragment如果menu/xyz_menu.xml中的MenuItem的ID与navigation/xyz_nav.xml中的目标的ID相匹配，则NavController可以导航至该目标。

请遵循官方文档中提到的正确步骤： https : //developer.android.com/guide/navigation/navigation-ui#Tie-navdrawer

注意：他们有一个示例应用程序链接到您可以参考的同一篇文章。