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BottomNavigation, FragmentManager has not been attached to a host

I have moved BottomNavigation codes from MainActivity to A class I have created for the BottomNaviction to make the code more organizing. When I moved the codes I got this error java.lang.RuntimeException: Unable to start activity ComponentInfo{com.moataz.mox/com.moataz.mox.ui.view.activity.MainActivity}: java.lang.IllegalStateException: FragmentManager has not been attached to a host. Short error message FragmentManager has not been attached to a host.
And The error In this line of code
// The error is here
final FragmentManager fragmentManager = fragmentActivity.getSupportFragmentManager();
Here's My BottomNavigation Class
public class BottomNavigation extends BottomNavigationView {
FragmentActivity fragmentActivity = new FragmentActivity();
final Fragment homeFragment = new HomeFragment();
final Fragment searchFragment = new SearchFragment();
final Fragment videosFragment = new VideosFragment();
final Fragment favouriteFragment = new FavouriteFragment();
final Fragment premiumFragment = new PremiumFragment();
// The error is here
final FragmentManager fragmentManager = fragmentActivity.getSupportFragmentManager();
Fragment mainFragment = homeFragment;
public BottomNavigation(#NonNull Context context) {
super(context);
}
#SuppressLint("NonConstantResourceId")
public void initializeBottomNavigation() {
// first one transaction to add each Fragment
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.fragment_layout, premiumFragment, "5").hide(premiumFragment);
fragmentTransaction.add(R.id.fragment_layout, favouriteFragment, "4").hide(favouriteFragment);
fragmentTransaction.add(R.id.fragment_layout, videosFragment, "3").hide(videosFragment);
fragmentTransaction.add(R.id.fragment_layout, searchFragment, "2").hide(searchFragment);
fragmentTransaction.add(R.id.fragment_layout, homeFragment, "1");
// commit once! to finish the transaction
fragmentTransaction.commit();
// show and hide them when click on BottomNav items
BottomNavigationView navigationView = findViewById(R.id.bottom_navigation);
navigationView.setOnItemSelectedListener(item -> {
// start a new transaction
FragmentTransaction localFragmentTransaction = fragmentManager.beginTransaction();
// TODO: ADD Animations
switch (item.getItemId()) {
case R.id.home_item:
localFragmentTransaction.hide(mainFragment).show(homeFragment).commit();
mainFragment = homeFragment;
return true;
case R.id.search_item:
localFragmentTransaction.hide(mainFragment).show(searchFragment).commit();
mainFragment = searchFragment;
return true;
case R.id.videos_item:
localFragmentTransaction.hide(mainFragment).show(videosFragment).commit();
mainFragment = videosFragment;
return true;
case R.id.saved_item:
localFragmentTransaction.hide(mainFragment).show(favouriteFragment).commit();
mainFragment = favouriteFragment;
return true;
case R.id.premium_item:
localFragmentTransaction.hide(mainFragment).show(premiumFragment).commit();
mainFragment = premiumFragment;
return true;
}
return false;
});
}
And here I haved Called my class and method In MainActivity
private void initializeBottomNavigation() {
BottomNavigation bottomNavigation = new BottomNavigation(this);
bottomNavigation.initializeBottomNavigation();
}
I have tried to find a sloution and anderstand the error but I didn't found sothing In my case. So what is the problem here and How can I fix It?

You cannot make a new instance of an activity; activity instances are built only by Android itself. The only thing you can do in order to obtain an activity reference is to use an existing one.
public class BottomNavigation extends BottomNavigationView {
final FragmentActivity fragmentActivity;
...
final FragmentManager fragmentManager;
public BottomNavigation(#NonNull Context context, #NonNull FragmentActivity activity) {
super(context);
fragmentActivity = activity;
fragmentManager = fragmentActivity.getSupportFragmentManager();
}
...
}
And pass your existing reference of your activity:
private void initializeBottomNavigation() {
FragmentActivity activity = this; // Or your activity reference
BottomNavigation bottomNavigation = new BottomNavigation(this, activity);
bottomNavigation.initializeBottomNavigation();
}
Note that you still need to attach your BottomNavigation to a view parent in the activity to make it visible.

Map fragment is not hidden when switch between fragments Android Studio

I'm trying to switch between fragments using a bottom navigation. However, if I switch to other fragments from the map fragment, the map fragment is still in the background while other fragment is being shown on the front.
Please see my code here:
public class MainActivity extends AppCompatActivity {
private FragmentManager fragmentManager;
private Fragment messageFragment = new MessageFragment();
private Fragment mapFragment = new MapsFragment();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().add(R.id.hostFragment, mapFragment, null).commit();
fragmentManager.beginTransaction().add(R.id.hostFragment, messageFragment, null).commit();
BottomNavigationView bottomNavigationView = findViewById(R.id.bottomNavigationView);
//bottomNavigationView.setSelectedItemId(R.id.mapsFragment);
bottomNavigationView.setOnNavigationItemSelectedListener(navListener);
}
private BottomNavigationView.OnNavigationItemSelectedListener navListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.mapsFragment:
fragmentManager.beginTransaction().hide(messageFragment).show(mapFragment).commit();
break;
case R.id.messageFragment:
fragmentManager.beginTransaction().hide(mapFragment).show(messageFragment).commit();
break;
}
return true;
}
};
}

Your Problem
You are adding both fragments to the same container, R.id.hostFragment.
fragmentManager.beginTransaction().add(R.id.hostFragment, mapFragment, null).commit();
fragmentManager.beginTransaction().add(R.id.hostFragment, messageFragment, null).commit();
Per the documentation for hide and show, this means that you are hiding and then showing the same container.
A Solution
Use two different container views:
fragmentManager.beginTransaction().add(R.id.mapContainer, mapFragment, null).commit();
fragmentManager.beginTransaction().add(R.id.messageContainer, messageFragment, null).commit();
Another Solution
Use replace instead of hiding and showing.
fragmentManager.beginTransaction().add(R.id.hostFragment, mapFragment, null).commit();
// Don't add this in `onCreate`
// fragmentManager.beginTransaction().add(R.id.hostFragment, messageFragment, null).commit();
...
// Replace the fragment currently being displayed
switch (item.getItemId()) {
case R.id.mapsFragment:
fragmentManager.beginTransaction().replace(R.id.hostFragment, mapFragment).commit();
break;
case R.id.messageFragment:
fragmentManager.beginTransaction().replace(R.id.hostFragment, messageFragment).commit();
break;
}

No view found for id when using Fragments

I've done everything I can find to fix my problem, it's the same as many others with the fragmentmanager that can't find a view.
Tried everything I have found online and could think about.
Heres my MainActivity.java
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MenuFragment menuFragment = new MenuFragment();
FragmentManager fmStart = getSupportFragmentManager();
FragmentTransaction fmTrans = fmStart.beginTransaction();
fmTrans.add(R.id.fragmentContainerID, menuFragment);
fmTrans.commitAllowingStateLoss();
}
public void addFragment(Fragment fragment, boolean addToBackStack, String tag) {
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
if (addToBackStack) {
ft.addToBackStack(tag);
}
ft.replace(R.id.fragmentContainerID, fragment, tag);
ft.commitAllowingStateLoss();
}
}
The error I get is the same as many others:
java.lang.IllegalArgumentException: No view found for id 0x7f080073 (se.iteda.hangman:id/fragmentContainerID) for fragment MenuFragment{d8a58aa (60d879ee-e84c-425e-a1a1-8e9be9c3b3a8) id=0x7f080073}
What I want to do is load a fragment at the start (MenuFragment) and in that fragment, I have 2 buttons that change fragments.

Ok. I opened your project in Github.
Error is here:
MainActivity.java
#Override
protected void onCreate(Bundle savedInstanceState) {
....
fmTrans.add(R.id.fragmentContainerID, menuFragment);
....
}
You are adding the fragment into fragmentContainerID. However, that view was not added to the Activity (leading to the view not found error).
So, in order to fix, I think you just need to apply the layout to the main activity. Something like:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Add this after super.onCreate()
setContentView(R.layout.activity_main);
.....
}
EDIT
And as I said in one of my comments, I think you don't need the code below at MenuFragment.java. I think you can remove it.
MenuFragment menuFragment = new MenuFragment();
((MainActivity)getActivity()).addFragment(menuFragment, true, "Menu");

Unable to set text in fragment

I am trying to call a function from my mainActivity to change a TextView in one of my fragments. I have read a couple posts on the best way of doing it but for some reason, none of them seem to work for me. I know the function is working because once a press the button the toast comes up but for some reason the text won't change. I was wondering what the issue could be, or if I am just missing an additional step.
here is the method being called in my mainActivity
public class MainActivity extends AppCompatActivity implements Tab1Fragment.OnCalcClickListener{
private static final String TAG = "MainActivity";
private SectionsPageAdapter mSectionsPageAdpater;
private ViewPager mViewPager;
Tab1Fragment tab1Fragment = new Tab1Fragment();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d(TAG, "onCreate: Starting");
//initializing FragmentManager so the fragments can communicate
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.container, tab1Fragment);
fragmentTransaction.commit();
//declare sections page adapter
mSectionsPageAdpater = new SectionsPageAdapter(getSupportFragmentManager());
//Set up the view pager with the sections adapter
mViewPager = (ViewPager) findViewById(R.id.container);
setUpViewPager(mViewPager);
//create a tab layout object and set it's id to tabs (mainActivity.xml)
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
//
}
// create a sections page view adapter
private void setUpViewPager(ViewPager viewPager){
SectionsPageAdapter adapter = new SectionsPageAdapter(getSupportFragmentManager());
adapter.addFragment(new Tab1Fragment(), "Day");
adapter.addFragment(new Tab2Fragment(), "Info");
adapter.addFragment(new Tab3Fragment(), "Week");
viewPager.setAdapter(adapter);
}
//initialise calculator object
Calculator mainCalculator = new Calculator();
#Override
public void calculateClick(int to_calculate) {
switch (to_calculate){
case 1:
Toast.makeText(getBaseContext(),"working", Toast.LENGTH_SHORT).show();
mainCalculator.freqDay = mainCalculator.freqDay + 1;
mainCalculator.freqWeek = mainCalculator.freqWeek + 1;
mainCalculator.getTotalDay();
tab1Fragment.updateInfo();
break;
}
}
Here is the code for my fragment
public class Tab1Fragment extends Fragment implements
View.OnClickListener{
private static final String TAG = "Tab1Fragment";
//Establishing the buttons & Methods
Button btn1;
Button btn2;
TextView dayView;
OnCalcClickListener onCalcClickListener;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.tab1_fragment, container, false);
//Connecting the buttons to the xml
btn1 = (Button) view.findViewById(R.id.btn_1);
btn1.setOnClickListener(this);
btn2 = (Button) view.findViewById(R.id.btn_2);
btn2.setOnClickListener(this);
dayView = (TextView) view.findViewById(R.id.total_Sales_Day);
return view;
}
//Onclick listener for buttons
public void setOnClickListener(View.OnClickListener listener) {
btn1.setOnClickListener(listener);
btn2.setOnClickListener(listener);
}
//method that will bring data back from activity and set the text
public void updateInfo(){
Toast.makeText(getContext(),"65", Toast.LENGTH_SHORT).show();
dayView.setText("test");
}

To make calls to methods from your fragment in the activity class you need something like this:
public static class MainActivity extends Activity
implements HeadlinesFragment.OnHeadlineSelectedListener{
...
public void onArticleSelected(int position) {
// The user selected the headline of an article from the HeadlinesFragment
// Do something here to display that article
ArticleFragment articleFrag = (ArticleFragment)
getSupportFragmentManager().findFragmentById(R.id.article_fragment);
if (articleFrag != null) {
// If article frag is available, we're in two-pane layout...
// Call a method in the ArticleFragment to update its content
articleFrag.updateArticleView(position);
} else {
// Otherwise, we're in the one-pane layout and must swap frags...
// Create fragment and give it an argument for the selected article
ArticleFragment newFragment = new ArticleFragment();
Bundle args = new Bundle();
args.putInt(ArticleFragment.ARG_POSITION, position);
newFragment.setArguments(args);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
}
}
}
Here the activity is calling the updateArticleView method from the fragment, instead of your updateInfo method, but you will get the idea.
Also pay attention to the one-pane scenario, where you need to swap the content and push the arguments using a Bundle object.
See Deliver a Message to a Fragment for more details.

When you add the fragment set a tag to it like this:
MyFragment frag = new MyFragment();
frag.setArguments(getIntent().getExtras());
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, frag, "TAG").commit();
While updating the textview get the instance of fragment using findFragmentByTag()
MyFragment fragment = (MyFragment) getSupportFragmentManager().findFragmentByTag("TAG");
fragment.updateInfo();

Why is accessing TextView of a Fragment inside Activity throwing an error

MainActivity class:
/* all necessary imports */
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
/* Other variable initialized here... */
FragOne fo;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
fo.setTextViewText("This is added from Activity");
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new FragOne(), "My Tracker");
adapter.addFragment(new FragTwo(), "Team Tracker");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
Fragment class:
/* all necessary imports */
public class FragOne extends Fragment {
TextView tvCName;
public FragOne() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_frag_one, container, false);
return view;
//return inflater.inflate(R.layout.fragment_frag_one, container, false);
}
#Override
public void onViewCreated(View view , Bundle savedInstanceState) {
tvCName = (TextView) view.findViewById(R.id.tvctq);
}
public void setTextViewText(String value){
tvCName.setText(value);
}
}
Fragment XML Layout:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.mytip.FragOne">
<TextView
android:text="TextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/tvctq" />
</FrameLayout>
I am trying to access the TextView inside the Fragment from MainActivity like this:
FragOne fo;
fo.setTextViewText("This is added from Activity");
I keep getting a NullPointerExceptionError. I looked at all the articles to see how to access, however none of them helped me.
Can someone please let me know what am I doing wrong and how to fix it?
I also plan on adding other Views inside my Fragment that I would need to access in the future.

Because fo hasn't been initialized in the following code snippet:
FragOne fo;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
fo.setTextViewText("This is added from Activity");
...
}
fo.setTextViewText() reasonably throws NPE.

You have to pay attention to the Activity lifecycle - you seem to be setting everything up correctly, but making a few mistakes accessing the correct instance of the fragment at the time it's actually ready. Things you should do
Get proper instance of the fragment from your ViewPager, like #ginomempin suggested;
Only try to set your text no earlier then your activities onStart method has been called - I usually do it onResume method (you can override it if you haven't already). Doing it in onResume method in the activity makes sure your Fragment has already gone through it's lifecycle up till onResume as well, and data will refresh if it has been brought to the background previously.
Here's a lifecycle diagram for your reference:

You need to use your Fragment factory method when creating your Fragment in your activity. Please see below:
**
Back Stack
**
The transaction in which fragments are modified can be placed on an internal back-stack of the owning activity. When the user presses back in the activity, any transactions on the back stack are popped off before the activity itself is finished.
For example, consider this simple fragment that is instantiated with an integer argument and displays that in a TextView in its UI:
public static class CountingFragment extends Fragment {
int mNum;
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static CountingFragment newInstance(int num) {
CountingFragment f = new CountingFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.hello_world, container, false);
View tv = v.findViewById(R.id.text);
((TextView)tv).setText("Fragment #" + mNum);
tv.setBackgroundDrawable(getResources().getDrawable(android.R.drawable.gallery_thumb));
return v;
}
}
A function that creates a new instance of the fragment, replacing whatever current fragment instance is being shown and pushing that change on to the back stack could be written as:
void addFragmentToStack() {
mStackLevel++;
// Instantiate a new fragment.
Fragment newFragment = CountingFragment.newInstance(mStackLevel);
// Add the fragment to the activity, pushing this transaction
// on to the back stack.
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.simple_fragment, newFragment);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();
}
After each call to this function, a new entry is on the stack, and pressing back will pop it to return the user to whatever previous state the activity UI was in.
Source: https://developer.android.com/reference/android/app/Fragment.html

You need to get the same instance of FragOne from the viewpager.
First, you can only access the FragOne instance after the ViewPager is setup.
Then, try this:
fo = adapter.getItem(0)
Note:
Since you already have fragments, it would be better to let the fragment itself handle the UI-related actions (such as setting the textview) rather than from the Activity.