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Swipe between fragments with help of BottomNavigationBar

I have trouble finding a good example on how to swipe between fragments with help of bottom navigatiom bar. Since FragmentStatePagerAdapter is deprecated and a new ViewPager2 is now recommended instead of the old ViewPager I want to use ViewPager2 and FragmentStateAdapter in my code instead. I have found an example of how to combine BottomNavigationBar and ViewPager here and I want to do something similar. My code have many similarities to the one in the example with the only difference that I have my code in a fragment instead of an activity. Here is a picture of how my FrontendFragment display look like. I can switch between the views using the bottomnavigationbar but I also want to be able to swipe between the views. Can someone help me or at least direct me on the right way? Here is my code:
FragmentPagerAdapter Class:
public class FragmentPagerAdapter extends FragmentStateAdapter {
private static final int mFragmentCount = 5;
public FragmentPagerAdapter(#NonNull Fragment fragment) {
super(fragment);
}
#NonNull
#Override
public Fragment createFragment(int position) {
switch (position){
case 0:
return new HomeFragment();
case 1:
return new SearchFragment();
case 2:
return new AddFragment();
case 3:
return new MessageFragment();
case 4:
return new ProfileFragment();
}
return null;
}
#Override
public int getItemCount() {
return mFragmentCount;
}
}
FrontendFragment Class:
public class FrontendFragment extends Fragment implements BottomNavigationView.OnNavigationItemSelectedListener{
private BottomNavigationView mBottomNavigationView;
private ViewPager2 mViewPager2;
private FragmentPagerAdapter mFragmentPagerAdapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.fragment_frontend, container, false);
loadFragment(new HomeFragment());
mBottomNavigationView = v.findViewById(R.id.bottomNavigationBar);
mBottomNavigationView.setOnNavigationItemSelectedListener(this);
return v;
}
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
Fragment selectedFragment = null;
switch (item.getItemId()) {
case R.id.home_icon:
selectedFragment = new HomeFragment();
break;
case R.id.search_icon:
selectedFragment = new SearchFragment();
break;
case R.id.add_icon:
selectedFragment = new AddFragment();
break;
case R.id.message_icon:
selectedFragment = new MessageFragment();
break;
case R.id.profile_icon:
selectedFragment = new ProfileFragment();
break;
}
return loadFragment(selectedFragment);
}
private boolean loadFragment(Fragment selectedFragment) {
if(selectedFragment != null){
MainActivity.sFm.beginTransaction().replace(R.id.relLayoutMiddle, selectedFragment).commit();
return true;
}
return false;
}
}
Thanks in advance!

As I'm already using BottomNav with ViewPager2 in one of my app, I can help.
Your code is partially correct which means your FragmentPagerAdapter is fine, but not your FrontEndFragment.
See, the FragmentPagerAdapter has to be set to a ViewPager2 as
//this here is the FrontEndFragment
mViewPager2.setAdapter(new FragmentPagerAdapter(this));
Then, You don't have to do the FragmentTransaction at all, you just have to change the ViewPager2's current item position through the BottomNavigationBar as
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.home_icon:
mViewPager2.setCurrentItem(0);
break;
case R.id.search_icon:
mViewPager2.setCurrentItem(1);
break;
case R.id.add_icon:
mViewPager2.setCurrentItem(2);
break;
case R.id.message_icon:
mViewPager2.setCurrentItem(3);
break;
case R.id.profile_icon:
mViewPager2.setCurrentItem(4);
break;
}
return false;
}
This is all, you don't have to deal with Fragments at all apart from the FragmentPagerAdapter. Also, don't forget to remove the loadFragment(new HomeFragment()); which is not required, nor the function loadFragment() is required.
(Optional), Furthermore, if you want to disable the Swipe Action of the ViewPager2 and want the Fragments to be selected based on the Selected BottomNav item only, then you can set setUserInputEnabled() property of ViewPager2 as false.
Next, to set the BottomNavigationBar's item as selected based on the swipe of the ViewPager2, what you've to do is,
Create a global var
MenuItem previousMenuItem;
Then, set a default item (first) to be selected of BottomNav on activity start as
mBottomNavigationView.getMenu().getItem(0).setChecked(true);
Finally, set an OnPageSelected() callback on ViewPager2 to update the selected Menu Item as:
mViewPager2.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
super.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
#Override
public void onPageSelected(int position) {
super.onPageSelected(position);
if (previousMenuItem != null) {
previousMenuItem.setChecked(false);
}
else {
mBottomNavigationView.getMenu().getItem(0).setChecked(false);
}
mBottomNavigationView.getMenu().getItem(position).setChecked(true);
previousMenuItem = mBottomNavigationView.getMenu().getItem(position);
}
#Override
public void onPageScrollStateChanged(int state) {
super.onPageScrollStateChanged(state);
}
});
What you're doing here is that you're setting default item to previousMenuItem and then on swiping to a different page, deselecting the previousMenuItem and selecting the new one, which means updating the BottomNav based on ViewPager's current item. This is the complete code you require to acheive your objective.

If you want to swipe between views, a simple solution would be to store all views in your parent view, but set all layouts for views except the initial view to android:visibility="gone". Make sure to set the initial view layout to android:visibility="visible" though. Now on you button clicks, you will have to implement onClick such that they turn on/ off view visibilities accordingly. For example, store views in order and control them via array index. But the whole thing you're trying to do is generally not a good design pattern in my opinion.
Why don't you load another Activity onClick instead of crowding your single activity? This will cause load time issues. Even if the views are non-visible, it's just an overall hassle to maintain all that in one place.

How to get last Fragment used when pressing back button

I have a simple fragment with this code:
private BottomNavigationView.OnNavigationItemSelectedListener navListener =
new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem menuItem) {
Fragment selectedFragment= null;
switch (menuItem.getItemId()){
case R.id.nav_home:
selectedFragment= new HomeFragment();
setTitle("Beranda");
break;
case R.id.nav_message:
selectedFragment= new MessageFragment();
setTitle("Pesan");
break;
case R.id.nav_transaction:
selectedFragment= new TransactionFragment();
setTitle("Transaksi");
break;
case R.id.nav_profile:
selectedFragment= new ProfileFragment();
setTitle("Profil");
if(sessionLevel.equals("admin")){
setTitle("Admin");
}
break;
}
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, selectedFragment).commit();
return true;
}
};
Most of the fragment are just some kind of holder for Intent Activity. And the Activity itself doesnt have some fancy code.
The problem is that when i do Intent on Profile menu and then press back, the fragment shown is HomeActivity but the selected button is Profile.
I dont know about the other 2 fragment since im not there yet, but probably they do the same thing.

You can do this like the following:
#Override
public void onBackPressed() {
super.onBackPressed();
Fragment frag = YourActivity.this.getSupportFragmentManager().findFragmentById(R.id.fragment_container);
if(frag!=null && frag instanceof yourFragment)
{}
}
The following will give you count
int count = getSupportFragmentManager().getBackStackEntryCount();
You can make condition, If count is great than 1 then have more than 1 fragments else you have atleast 1 fragment and that will be last fragment. If count 0 then no more fragment available on stack as all have been poped out of stack.

Create an interface:
public interface IOnBackPressed {
boolean onBackPressed();
}
In Fragment implement IOnBackPressed like:
public class FAQFragment extends Fragment implements IOnBackPressed {
public boolean onBackPressed() {
return false
}
}
On Main Activity Backpress use
#Override
public void onBackPressed(){
if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
getSupportFragmentManager().popBackStack();
}
}

Fragment Transaction shows Tabs Fragment below

I'm making an app that has launches with a Swiping Tabs Fragment, but I also want to have a Preferences menu using Fragment Transaction. When I press the Settings button in my app, the preferences menu does appear and is interactive, but the layout seems to be transparent showing the Tabs below. Is there anything that can be done to fix this, or is there a better method?
Code that calls the Preferences Menu from the Options:
public boolean onOptionsItemSelected(final MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
getFragmentManager().popBackStackImmediate();
break;
case R.id.logout:
FirebaseAuth.getInstance().signOut();
finish();
startActivity(new Intent(this, Activity_Main.class));
break;
case R.id.action_settings:
getFragmentManager().beginTransaction()
.replace(android.R.id.content, new Fragment_Settings()).addToBackStack(null)
.commit();
break;
}
return true;
}
Code that calls Tabs Fragments:
public class TabsPagerAdapter extends FragmentPagerAdapter {
public TabsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public android.support.v4.app.Fragment getItem(int index) {
switch (index) {
case 0:
// Top Rated fragment activity
return new Fragment_Flower();
case 1:
// Games fragment activity
return new Fragment_Overview();
}
return null;
}
#Override
public int getCount() {
// get item count - equal to number of tabs
return 2;
}
}
Initialising Transaction in onCreate:
startService(new Intent(this, SensorListener.class));
if (b == null) {
// Create new fragment and transaction
Fragment newFragment = new Fragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
//Replace whatever is in the fragment_container view with this
// fragment,
// and add the transaction to the back stack
transaction.replace(android.R.id.content, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
}
Any help will be greatly appreciated!

Just set background color in your layout file. It may avoid transparent backgound.

SlidingTabLayout, Restarts fragment On case 4 to 1?

my SlidingTabLayout restarts my fragment dashboard activity when switching from fragment tags to fragment dashboard, or position 4 to 0.
Here is the code that I have written so far, can anyone shed some light on the situation ?
public class SectionsPagerAdapter extends FragmentStatePagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
//2 steps creating a fragment, create the fragment class and create the UI for it
Fragment fragment = null;
//we dont want it to return our place holder Fragment instead we want to switch bewtween 3
//create a switch case based on the position applied or the fragment selected
switch (position) {
case HOME:
fragment = Dashboard.newInstance("","");
break;
case TAGS:
fragment = Tags.newInstance("","");
break;
case MY_RECENT:
fragment = MyPosts.newInstance("","");
break;
case TOP:
fragment = Top.newInstance("", "");
break;
}
return fragment;
}
#Override
public int getCount() {
// Show 3 total pages.
return 4;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Home";
case 1:
return "Top";
case 2:
return "Recent";
case 3:
return "Tags";
}
return null;
}
}

You have to load all fragment in one time, you should call this method
int size=4;
viewPager.setOffscreenPageLimit(size);
after set adapter, size is the no of fragment which you want to load first time

Viewpager not saving Fragment states

First of all I would like to thank the stackoverflow community. Thanks to you I solved so much problems! Usually I bang my head over the wall for hours and I find the solution here (98% percent of the time). This time I would like to share my problem.
This is the first app I'm developing. I have one activity (is this bad?). My app structure is the following: Nav drawer which contains four items - two viewpagers and two static fragments. The viewpagers contains lists with data and if you click on one of the items from the list you are present with a detail page which again is a viewpager. When you are on the detail page you can click and advance to other fragment. The problem is that when I advance to the other fragment onSavedInstance is not called for the viewpagerdetails and I can't retain the fragment state. onSavedInstance will be called if I pass to the FragmentPagerAdapter getFragmentManager(), instead of getChildFragmentManager(), but if I do this when I navigate back, the viewpager items are blank. I have tried using FragmentStatePagerAdapter, but when I click back from the 'other fragment' to return to viewpager details the app crashes with the following error: Fragment no longer exists for key f0: index 0. I have looked over the internet, but I didn't found a working solution. Some say that the problem is from the adapter, but I tried this solution and it didn't work. Also I want to manually retain my fragment state, please don't offer me the fix with the configchanges in the app manifest. I have tried to call onSavedInstanceState from the onStop method, but when I return to the fragment the saved state is empty. Should I implement this with a static variable in my mainActivity?
FragmentPagerAdapter:
public class DetailsSlideAdapter extends FragmentPagerAdapter {
private String[] navMenuTitles;
private FragmentManager manager;
private FragmentTransaction mCurTransaction = null;
private Resources res;
public DetailsSlideAdapter(FragmentManager fm, Resources res) {
super(fm);
this.manager = fm;
navMenuTitles = res.getStringArray(R.array.detailTabs);
this.res = res;
}
#Override
public int getCount() {
return 3;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
DetailsInfo info = new DetailsInfo();
return info;
case 1:
DetailsCast cast = new DetailsCast();
return cast;
case 2:
DetailsOverview overview = new DetailsOverview();
return overview;
default:
return null;
}
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return navMenuTitles[0];
case 1:
return navMenuTitles[1];
case 2:
return navMenuTitles[2];
default:
return navMenuTitles[1];
}
}
Viewpager details:
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// Get the ViewPager and set it's PagerAdapter so that it can display items
DetailsSlideAdapter = new DetailsSlideAdapter(getChildFragmentManager(), getResources());
mViewPager = (ViewPager) rootView.findViewById(R.id.DetailsPager);
mViewPager.setOffscreenPageLimit(3);
mViewPager.setAdapter(DetailsSlideAdapter);
// Give the SlidingTabLayout the ViewPager, this must be done AFTER the ViewPager has had
// it's PagerAdapter set.
mSlidingTabLayout = (DetailsSlidingTabLayout) rootView.findViewById(R.id.sliding_tabs);
mSlidingTabLayout.setViewPager(mViewPager);
mSlidingTabLayout.setSelectedIndicatorColors(getResources().getColor(R.color.tabSelected));
}
If other code is needed I will post it. Thanks.
EDIT using FragmentStateAdapter:
App crashes: Fragment no longer exists for key f0: index 0. On the internet people say that the problem is from the adapter, but I tried this solution and it didn't work. Code:
public class DetailsSlideAdapter extends FragmentStatePagerAdapter {
private String[] navMenuTitles;
private FragmentManager manager;
private FragmentTransaction mCurTransaction = null;
private Resources res;
SparseArray<Fragment> registeredFragments = new SparseArray<Fragment>();
public DetailsSlideAdapter(FragmentManager fm, Resources res) {
super(fm);
this.manager = fm;
navMenuTitles = res.getStringArray(R.array.detailTabs);
this.res = res;
}
#Override
public int getCount() {
return 3;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
DetailsInfo info = new DetailsInfo();
return info;
case 1:
DetailsCast cast = new DetailsCast();
return cast;
case 2:
DetailsOverview overview = new DetailsOverview();
return overview;
default:
return null;
}
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return navMenuTitles[0];
case 1:
return navMenuTitles[1];
case 2:
return navMenuTitles[2];
default:
return navMenuTitles[1];
}
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment fragment = (Fragment) super.instantiateItem(container, position);
registeredFragments.put(position, fragment);
return fragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
registeredFragments.remove(position);
super.destroyItem(container, position, object);
}
public Fragment getRegisteredFragment(int position) {
return registeredFragments.get(position);
}

Have you seen this? FragmentStatePagerAdapter
From the Docs:
Implementation of PagerAdapter that uses a Fragment to manage each
page. This class also handles saving and restoring of fragment's
state.