导航菜单片段无法初始化其布局的组件

Question

I've created a navigation menu fragment for my application so that i can use it across all of my activities. However, when i run the app the menu does not work neither when i click on the hamburger icon nor when i pull from left to right. So i decided to use the debugger and i found out that none of my fragment's layout components get initialized within the fragment's class. Can you help me figure out why this happens and how to fix it? Here is my fragment.java class and my fragment_layout.xml file:

Fragment.java:

public class NavMenuFragment extends Fragment {

// NavMenu member vars
private DrawerLayout mDrawerLayout;
private NavigationView navigationView;
private ActionBarDrawerToggle mToggle; // Button for toggling the side menu

// Keeps the position of the previously selected menu item(0 : Home)
int position = 0;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_nav_menu,null);
    mDrawerLayout = view.findViewById(R.id.drawerLayout);
    navigationView = view.findViewById(R.id.nav_view);
    mToggle = new ActionBarDrawerToggle(getActivity(),mDrawerLayout,R.string.drawer_open,R.string.drawer_closed); // Instantiating our button
    return view;
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    // Sets the default selected menu item, to the Home item
    navigationView.getMenu().findItem(R.id.nav_home).setChecked(true);

    // Used to help on check and uncheck menu items when the user clicks on them
    final List<MenuItem> items = new ArrayList<>();
    Menu menu;
    menu = navigationView.getMenu();

    // Fill the list with all the menu items
    for(int i=0; i<menu.size();i++) {
        items.add(menu.getItem(i));
    }

    Toast.makeText(getActivity(), "size:" + items.size(), Toast.LENGTH_SHORT).show();

    // When an item inside the NavView gets clicked, then handle the event...
    navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {

            switch (item.getItemId()) {
                case R.id.nav_home:
                    mDrawerLayout.closeDrawer(Gravity.START);
                    break;
                case R.id.nav_UserBoxGLB:
                    break;
                case R.id.nav_UserBoxJP:
                    break;
                case R.id.nav_settings:
                    break;
                case R.id.nav_feedback:
                    break;
                case R.id.nav_contact_us:
                    break;
                case R.id.nav_donate:
                    // Open the website's URL in a browser window
                    Intent intent = new Intent();
                    intent.setAction(Intent.ACTION_VIEW);
                    intent.addCategory(Intent.CATEGORY_BROWSABLE);
                    intent.setData(Uri.parse("http://www.google.com"));
                    startActivity(intent);
                    break;
                case R.id.nav_about:
                    break;
                default:
                    return onNavigationItemSelected(item);
            }
            items.get(position).setChecked(false);
            item.setChecked(true);
            mDrawerLayout.closeDrawers();
            return false;
        }
    });

    mDrawerLayout.addDrawerListener(mToggle);
    // Set the hamburger icon's color
    mToggle.getDrawerArrowDrawable().setColor(getResources().getColor(R.color.NavActionBarTextColor));
    mToggle.syncState();
}

// When an item from the Action Bar gets tapped, then...
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    return mToggle.onOptionsItemSelected(item) || onOptionsItemSelected(item);
}
}

Fragment_layout.xml:

 <android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_gravity="left"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorPrimary"
    android:id="@+id/drawerLayout">

    <!-- The actual side menu Nav View -->
    <android.support.design.widget.NavigationView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:headerLayout="@layout/navigation_header"
        app:menu="@menu/navigation_menu"
        android:id="@+id/nav_view">

    </android.support.design.widget.NavigationView>

</android.support.v4.widget.DrawerLayout>

Answer 1

You are doing it wrong
If you want to use same navigation drawer for all fragment then
You can make a navigation drawer in your main activity and open fragment from that navigation drawer.
Here is the tutorial