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BottomNavigationView with setOnItemSelectedListener()

I am trying to build app with BottomNavigationView and I set setOnItemSelectedListener() method to bottom navigation so I can do what I want when user select one of the menu in bottom navigation.
everything is good when I don't set setOnItemSelectedListener(), but when I set setOnItemSelectedListener() method then the fragment is not updated automatically when user select the bottom navigation menu.
I consider if that do i have to handle fragment transaction manually when I set this method?
thanks ^^

Yes. You need to manually replace the fragment item on onNavigationItemSelected
Example:
private BottomNavigationView.OnNavigationItemSelectedListener navListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
// By using switch we can easily get
// the selected fragment
// by using there id.
Fragment selectedFragment = null;
switch (item.getItemId()) {
case R.id.algorithm:
selectedFragment = new AlgorithmFragment();
break;
case R.id.course:
selectedFragment = new CourseFragment();
break;
case R.id.profile:
selectedFragment = new ProfileFragment();
break;
}
// It will help to replace the
// one fragment to other.
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.fragment_container, selectedFragment)
.commit();
return true;
}
};
You can find a good tutorial here: https://www.geeksforgeeks.org/bottomnavigationview-inandroid/

Why fragment is getting added to the back stack several times

I was trying to implement the bottom navigation with fragment inside an activity.
I have done that and it was successful.
To replace the fragment on click each navigation item, I use the following code.
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_notifications:
loadFragment(new NotificationsFragment());
return true;
case R.id.navigation_notes:
loadFragment(new NotesFragment());
return true;
case R.id.navigation_about:
loadFragment(new AboutFragment());
return true;
}
return false;
}
};
private void loadFragment(Fragment fragment) {
// load fragment
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_container, fragment);
transaction.addToBackStack(null);
transaction.commit();
}
Now the problem is that when I click on a navigation in the bottom navigation bar multiple times, the fragment is also getting added to the back stack multiple times.
So when I click the back button the fragment is again loaded, not exiting or loading the previous fragment.
So, How can I prevent the fragment getting added to the back stack multiple times?

Remove
transaction.addToBackStack(null);
or add
transaction.disallowAddToBackStack();

Android Fragment reset when replacing it

I'm currently developing a Android studio App using fragment and a bottom navigation bar.
When I click on a navigation bar's item, it's replacing the current fragment by another one which correspond the fragment I wanted for this item.
The problem is, the objects in my fragment are all reset after replacing fragment.
I'm not removing the fragment from the container so I don't really understand why all the objects are reset after doing this.
Here is my code to add and replace fragment to my FrameLayout :
private void setFragment(Fragment fragment) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.setCustomAnimations(android.R.anim.slide_in_left, android.R.anim.fade_out);
if (getSupportFragmentManager().findFragmentById(R.id.main_frame) == null) {
fragmentTransaction.add(R.id.main_frame, fragment);
}
else
{
fragmentTransaction.replace(R.id.main_frame, fragment);
}
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
and here is the bottom navigation bar code to execute the previous function and change the displayed fragment:
homeFragment = new HomeFragment();
programFragment = new ProgramFragment();
bluetoothFragment = new BluetoothFragment();
mMainNav.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
test = mMainNav.getMenu().getItem(2);
switch (item.getItemId()) {
case R.id.nav_home:
//mMainNav.setItemBackgroundResource(R.color.colorPrimary);
HQ_logo_IV.setVisibility(View.VISIBLE);
setFragment(homeFragment);
return true;
case R.id.nav_program:
//mMainNav.setItemBackgroundResource(R.color.colorAccent);
HQ_logo_IV.setVisibility(View.INVISIBLE);
setFragment(programFragment);
return true;
case R.id.nav_bluetooth:
//mMainNav.setItemBackgroundResource(R.color.colorPrimaryDark);
HQ_logo_IV.setVisibility(View.INVISIBLE);
setFragment(bluetoothFragment);
return true;
default:
return false;
}
}
});

I found the way to stop this thing.
I used an AsyncTask to refresh my fragment state.
I just put new "yourAsyncTaskName"().execute() at the beginning of my onCreate() method to refresh the fragment when it's created or replaced.
Hope this will help.

Correct Activity/Fragment Architecture for Android Bottom Navigation View

I would like to get some input on the best way to structure my app's architecture when using Android's Bottom Navigation View.
Currently I define my BottomNavigationView in my MainActivity. It looks something like this.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BottomNavigationView bottomNavigationView = (BottomNavigationView)findViewById(R.id.bottom_navigation);
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
Fragment selectedFragment = null;
switch (item.getItemId()){
case R.id.action_home:
selectedFragment = HomeFragment.newInstance();
break;
case R.id.action_search:
selectedFragment = SearchFragment.newInstance();
break;
case R.id.action_message:
selectedFragment = MessageFragment.newInstance();
break;
case R.id.action_profile:
selectedFragment = ProfileFragment.newInstance();
break;
}
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_layout, selectedFragment);
transaction.commit();
return true;
}
});
//Manually displaying the first fragment - one time only
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_layout, HomeFragment.newInstance());
transaction.commit();
}
The problem is that once I click on one tab, it opens up a fragment, and I would like to have those Fragments open up other Fragments/Activities (i.e:
I open the profile tab (`ProfileFragment` loads)
I click on a button from `ProfileFragment`, and from this the `SignUpFragment` or `SignUpActivity` loads
After running into many bugs, I've researched on how to architect my app, but i've found mixed results. Would anyone know the correct way of using a BottomNavigationView with Fragments, and in those fragments I can load more Activities/fragments. A huge thanks in advance.

Every approach depends on the project and what you pretend to achieve. I had to code a Bottom Navigation app that works with over 20 Bottom Navigation layouts, meaning one single Activity. The process you wish to achieve is pretty much the same of setting the desired fragment in the desired tab on tab selected, the difference is that, instead of taping on a tab, you will tap on a button inside a fragment, which you will replace with the new desired fragment.
tap tab -> replace fragment -> button click inside fragment -> replace fragment -> and so on.
Since you are using replace, you will have to carefully handle your onBackPress event, since I'm assuming that on every back press you wish to go back to the previous fragment. Myself, I've implemented an interface in the Main Activity that listens to the visible fragment onBackPress.

prevent same fragment multiple times in backstack

Hi guys here is my code
navigationView.setNavigationItemSelectedListener(new NavigationView
.OnNavigationItemSelectedListener() {
#Override public boolean onNavigationItemSelected(#NonNull MenuItem item) {
if (item.isChecked()) {
//item already selected. Do nothing
drawerLayout.closeDrawer(GravityCompat.START);
return true;
}
switch (item.getItemId()) {
case R.id.home:
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
transaction.replace(R.id.fragment, new HomeFragment())
.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE).commit();
break;
case R.id.other:
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment, new OtherFragment())
.addToBackStack(null).setTransition(FragmentTransaction
.TRANSIT_FRAGMENT_FADE).commit();
break;
default:
break;
}
drawerLayout.closeDrawer(GravityCompat.START);
return true;
}
});
I basically only have 2 fragments and merely the HomeFragment should be added to the backstack. After switching between HomeFragment and OtherFragment for a while and clicking on the back button while on the HomeFragment, I end up with the HomeFragment getting displayed several times.
Within the HomeFragment lies a recyclerview. When I scroll up and down I can really see that the rows are displayed multiple times.
How can I make sure that the HomeFragment is added to the backstack only once.
Thanks

You could easily check your fragment with
YourFragment.isAdded
And if you have a multiple fragment you could create a new class to manage all the fragment and create state to check if fragment have been added or not.

When you click on the Home menu item try to find out whether there is any fragment in the backstack or not. If yes, call popBackStack() or replace a fragment as you do now otherwise. Use this code: if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
getSupportFragmentManager().popBackStack();
}