在我的MainActivity.java课堂上，我有一个名为的起始片段MainScreenFragment.java，它按预期工作。但是，当用户单击我的第二个菜单项时，我drawer-layout将其替换为另一个名为UserBoxGLBFragment.java. 通过使用 Log.d(); 在里面调用onCreateView，onViewCreated我发布了 UserBoxGLBFragment 的方法根本不会被调用（这可能是我看不到它的内容的原因）。你能帮我弄清楚为什么会这样吗？以下是课程：
MainActivity.java：
public class MainActivity extends AppCompatActivity {
private Toolbar mToolbar;
// 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;
// Declaring our dialog
ImportantDialogFragment dialogFragment = new ImportantDialogFragment();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Showing the disclaimer dialog every time the app starts
dialogFragment.show(getSupportFragmentManager(),"IMPORTANT_NOTICE");
mDrawerLayout = findViewById(R.id.drawerLayout);
navigationView = findViewById(R.id.nav_view);
mToggle = new ActionBarDrawerToggle(this,mDrawerLayout,R.string.drawer_open,R.string.drawer_closed); // Instantiating our button
mToolbar = findViewById(R.id.navActionBar);
setSupportActionBar(mToolbar); // check quick doq
getSupportActionBar().setDisplayShowTitleEnabled(false);
mToolbar.setTitle("");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// 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(this, "size:" + items.size(), Toast.LENGTH_SHORT).show();
// Set the default starting screen to the mainScreen
FragmentManager startingScreenManager = getSupportFragmentManager();
FragmentTransaction startingScreenTransaction = startingScreenManager.beginTransaction();
MainScreenFragment fragment = new MainScreenFragment();
startingScreenTransaction.add(R.id.FrameLayoutContainer, fragment);
startingScreenTransaction.commit();
final UserBoxGLBFragment glbFragment = new UserBoxGLBFragment();
// When an item inside the NavView gets clicked, then handle the event...
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
// Initializing these vars again for use in this inner class
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
// Replace the main Fragment in this activity based on the menu item selected
switch (item.getItemId()) {
case R.id.nav_home:
MainScreenFragment mainScreenFragment = new MainScreenFragment();
fragmentTransaction.replace(R.id.FrameLayoutContainer,mainScreenFragment);
fragmentTransaction.commit();
break;
case R.id.nav_UserBoxGLB:
//UserBoxGLBFragment glbFragment = new UserBoxGLBFragment();
fragmentTransaction.replace(R.id.FrameLayoutContainer,glbFragment);
fragmentTransaction.commit();
break;
case R.id.nav_UserBoxJP:
break;
case R.id.nav_events:
Toast.makeText(MainActivity.this, "Events are not available yet! Sorry", Toast.LENGTH_SHORT).show();
break;
case R.id.nav_feedback:
composeEmail(emails,"Feedback", "[Your message here]");
break;
case R.id.nav_contact_us:
composeEmail(emails,"Contact Us", "[Your message here]");
break;
case R.id.nav_website:
// 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:
Intent aboutIntent = new Intent(MainActivity.this, AboutPageActivity.class);
startActivity(aboutIntent);
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);
}
private String[] emails = {"SPDesignsOfficial@outlook.com"};
/**
* Send an email to the @adress with a @subject
* @param addresses The email adress(es) to send the email to
* @param subject The email's subject
*/
public void composeEmail(String[] addresses, String subject, String message) {
Intent intent = new Intent(Intent.ACTION_SENDTO);
intent.setData(Uri.parse("mailto:")); // only email apps should handle this
intent.putExtra(Intent.EXTRA_EMAIL, addresses);
intent.putExtra(Intent.EXTRA_SUBJECT, subject);
intent.putExtra(Intent.EXTRA_TEXT,message);
if (intent.resolveActivity(getPackageManager()) != null) {
startActivity(intent);
}
}
}
MainScreenFragment.java：
public class MainScreenFragment extends Fragment {
// Main Grid View
GridView gridView;
public MainScreenFragment() {
// Required empty public constructor
}
// Create a Context Menu when an item in the GridView is long-pressed
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
menu.setHeaderTitle("Card Options");
//AdapterView.AdapterContextMenuInfo cmi = (AdapterView.AdapterContextMenuInfo) menuInfo;
menu.add(1,v.getId(),0, "Add Card to GLB");
menu.add(2,v.getId(),0,"Add Card to JP");
}
// When an item in the context menu gets selected, call a method
@Override
public boolean onContextItemSelected(MenuItem item) {
// Get some extra info about the contextMenu
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
int position = info.position; // clicked view's position
if(item.getTitle().equals("Add Card to GLB")) {
addCardMessage(position, "added to GLB");
addSelectedCardToGlobalUserBox(position);
} else if (item.getTitle().equals("Add Card to JP")) {
addCardMessage(position , "added to JP");
} else
{
return false;
}
return false;
}
/**
* Creates a snackbar message, telling the user which card was added to which box
* @param id The position of the chosen card
* @param text Defines into which User Box the card was added
*/
private void addCardMessage(int id, String text) {
final Snackbar snackbar = Snackbar.make(gridView, id + " " + text ,Snackbar.LENGTH_LONG);
snackbar.setAction("Dismiss", new View.OnClickListener() {
@Override
public void onClick(View view) {
snackbar.dismiss();
}
});
snackbar.setActionTextColor(Color.MAGENTA);
snackbar.show();
}
UserBoxGLBFragment fragment = new UserBoxGLBFragment();
private void addSelectedCardToGlobalUserBox(int position) {
ImageAdapter imageAdapter = new ImageAdapter(getContext());
fragment.addInteger(imageAdapter.getmThumbIds(0)); // pass the Drawable's Integer value to the fragmnet
Toast.makeText(getActivity(), "Selected icon: " + imageAdapter.getmThumbIds(position), Toast.LENGTH_SHORT).show();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_main_screen, container, false);
gridView = view.findViewById(R.id.gridViewLayout);
gridView.setAdapter(new ImageAdapter(getContext())); // used to set the contents of the GridView-in this case images-
registerForContextMenu(gridView);
// When an item from the GridView gets clicked
gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// Create a new Intent...
Toast.makeText(getActivity(), "Position: " + position, Toast.LENGTH_SHORT).show();
Intent intent = new Intent(getContext(),CardViewActivity.class);
intent.putExtra("Card Index",position);
intent.putExtra("SCREEN_WIDTH",1080);
startActivity(intent);
}
});
return view;
}
}
用户框GLBFragment.java：
public class UserBoxGLBFragment extends Fragment {
GridView globalGridView;
UserBoxGlbImageAdapter adapter = new UserBoxGlbImageAdapter(getContext());
public UserBoxGLBFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d("OnViewCreated:" , "OnViewCreated called successfully!");
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_user_box_glb, container, false);
return view;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
globalGridView = view.findViewById(R.id.userBoxGlbGridView);
globalGridView.setAdapter(adapter);
Log.d("OnViewCreated:" , "OnViewCreated called successfully!");
}
public void addInteger(Integer integer) {
adapter.addDrawableToList(integer);
}
}