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how to use fragments backstack with shared element transition

shared element transition replace the fragment, so I can't add it to the backstack and call popbackstack when the back arrow button is pressed.
I have a main activity with inside a mainfragment, the main fragment handle a table layout so each tab is a fragment with inside a recycler view, when a recycler view element is clicked the shared element transition start to a new fragment that shows element details.
This is the adapter, where the element is clicked:
holder.image.setTransitionName("transition" + holder.getAdapterPosition());
if (fragment instanceof tab1_anime) {
((tab1_anime) fragment).openShowElementFragment(holder.getAdapterPosition(), v.findViewById(R.id.main_image));
}
This is the openShowElementFragment inside my tab fragment:
public void openShowElementFragment(int position, View view) {
AddElement element = anime_list.get(position);
ShowElementFragment showElementFragment = new ShowElementFragment();
Bundle bundle = new Bundle();
bundle.putString("transitionName", "transition" + position);
bundle.putSerializable("element", element);
bundle.putInt("position", position);
bundle.putInt("from", 0);
showElementFragment.setArguments(bundle);
((MainActivity) context).showFragmentWithTransition(this, showElementFragment, "showElementFragment", view, "transition" + position);
}
this is the openshowelementfragment function called in the previous code block:
public void showFragmentWithTransition(Fragment current, Fragment newFragment, String tag, View sharedView, String sharedElementName) {
FragmentManager fragmentManager = getSupportFragmentManager();
// check if the fragment is in back stack
boolean fragmentPopped = fragmentManager.popBackStackImmediate(tag, 0);
if (fragmentPopped) {
} else {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
current.setSharedElementReturnTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
current.setExitTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
newFragment.setSharedElementEnterTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
newFragment.setEnterTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
}
fragmentManager.beginTransaction()
.replace(R.id.fragmentHolder, newFragment)
.addToBackStack(null)
.addSharedElement(sharedView, sharedElementName)
.commit();
}
}
and this is the backarrow button:
back_arrow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
getSupportFragmentManager().popBackStack();
}
});
If I try to add the new fragment instead of replace the old one, then there is not animations at all.
If I try to replace the old fragment with the new one and using anyway the addtobackstack(null) then the shared element transition works from start to end BUT the fragment at the end is without data, empty:
I tried also:
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.fragmentHolder, new MainFragment())
.addToBackStack(null)
.commit();
but in this way the shared element transition doesn't work on exit:

I think your problem is related to exit transition as you get solution of empty list, now for exit transition effect check below code.
public void showFragmentWithTransition(Fragment current, Fragment newFragment, String tag, View sharedView, String sharedElementName) {
FragmentManager fragmentManager = getSupportFragmentManager();
// check if the fragment is in back stack
boolean fragmentPopped = fragmentManager.popBackStackImmediate(tag, 0);
if (fragmentPopped) {
} else {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
current.setSharedElementReturnTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
current.setExitTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
newFragment.setSharedElementEnterTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
newFragment.setEnterTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
newFragment.setExitTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
newFragment.setSharedElementReturnTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
}
getSupportFragmentManager().beginTransaction()
.addSharedElement(sharedElement, transitionName)
.replace(R.id.container, newFragment)
.addToBackStack(null)
.commit();
}
}
Here I add two new lines for exit transitions.
newFragment.setExitTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
newFragment.setSharedElementReturnTransition(TransitionInflater.from(this).inflateTransition(R.transition.default_transition));
If its not work then follow below link, I think it will help you.
https://medium.com/#bherbst/fragment-transitions-with-shared-elements-7c7d71d31cbb

Your so called sharedElementName is actually a transitionName.
a) The reference example doesn't directly manipulate the backstack:
Android Fragment Transitions: RecyclerView to ViewPager & Blog.
b) Manual transactions might require another order of method calls:
getSupportFragmentManager().beginTransaction()
.addSharedElement(sharedElement, transitionName)
.replace(R.id.container, newFragment)
.addToBackStack(null)
.commit();
Also see this example, how alternate transitions could be be set, compared to:
TransitionInflater.from(this).inflateTransition(R.transition.default_transition)
Whatever R.transition.default_transition may be.
It may look strange when using the same transition for both ways, instead of enter/exit transitions, alike NavAction would feature. FragmentNavigator.Extras could be used to apply enter/exit transitions, when using navigation component; this also can be combined with ActionBar. Option a) is probably less complicated. b) something alike this Kotlin example might make more sense.
It's pointless to build clunky navigation FX when enter/exit transitions would be supported out-of-the-box. Maybe consider loading with Glide, when loading images.
Assume the following build.gradle; there's no need to reinvent the wheel.
dependencies {
androidTestImplementation "androidx.navigation:navigation-testing:2.5.3"
implementation 'androidx.navigation:navigation-runtime:2.5.3'
implementation 'androidx.navigation:navigation-fragment:2.5.3'
implementation 'androidx.navigation:navigation-ui:2.5.3'
annotationProcessor 'com.github.bumptech.glide:compiler:4.14.2'
implementation 'com.github.bumptech.glide:glide:4.14.2'
}
Then Navigation with FragmentNavigator.Extras might rather be the current method:
Bundle navArgs = new Bundle();
navArgs.putInt("position", position);
FragmentNavigator.Extras extras = new FragmentNavigator.Extras.Builder()
.addSharedElement(sharedElement, transitionName)
.build();
Navigation.findNavController(view).navigate(
R.id.details, // ID of Nav destination
navArgs, // Bundle of args
null, // NavOptions
extras);
One can also define transitionName in XML <action/> nodes.

Where should I call Rest API in fragment

I'm using Bottom-navigation with 3 fragments. On Home-fragment I'm requesting API to fetch data and show in recycler-view my problem is whenever I switch fragments and come again to Home-fragment it's recreating the layout and again its fetch data from API I want to load only one time when app launch
This is where I call API in the fragment
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.home_fragment, container, false);
// return inflater.inflate(R.layout.home_fragment, container, false);
sharedPrefManager = new SharedPrefManager(getActivity());
locationTrack = new LocationTrack(getActivity());
buildGoogleApiClient();
fusedLocationClient = LocationServices.getFusedLocationProviderClient(getActivity());
getUserLatLng();
setUp(view);
netWorkCall();
return view;
}
HomeActivity to load home-fragment by default
if (savedInstanceState == null) {
Fragment fragment = null;
fragment = new HomeFragment();
if (fragment != null) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.content_frame, fragment, "home").addToBackStack("Home");
ft.commit();
}
}
bottom-navigation click listener
private void displaySelectedScreen(int itemId) {
Fragment fragment = null;
switch (itemId) {
case R.id.action_home:
fragment = new HomeFragment();
break;
case R.id.action_profile:
if (sharedPrefManager.getAuthority()) {
fragment = new ProfileFragment();
} else {
SDConstant.switchActivity(this, LoginScreen.class);
}
break;
case R.id.action_calculator:
if (sharedPrefManager.getAuthority()) {
fragment = new CalculatorFragment();
} else {
SDConstant.switchActivity(this, LoginScreen.class);
}
break;
}
//replacing the fragment
if (fragment != null) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, fragment, "home").addToBackStack("Home");
ft.commitAllowingStateLoss();
//ft.commitNow();
}
}
}
Please guide me solution How to solve this re-creation API call

First off, perform this calls inside onViewCreated instead of onCreateView:
sharedPrefManager = new SharedPrefManager(getActivity());
locationTrack = new LocationTrack(getActivity());
buildGoogleApiClient();
fusedLocationClient = LocationServices.getFusedLocationProviderClient(getActivity());
getUserLatLng();
setUp(view);
netWorkCall(); //this call has to be removed as explained later
Why? Because onCreateView should just return the fragments UI. OnViewCreated is called directly afterwards and this is the place to do some stuff.
No to get to your problem. The best way for you to solve this would be using a ViewModel from the architecture components in conjunction with LiveData.
You can read more on this topic here.
Your implementation could look like this (adapted the example from the link):
public class MyViewModel extends ViewModel {
private MutableLiveData<List<User>> users;
public LiveData<List<User>> getUsers() {
if (users == null) {
users = new MutableLiveData<List<User>>();
loadUsers();
}
return users;
}
private void loadUsers() {
// Do an asynchronous operation to fetch users.
}
}
In your onViewCreated you can do something lik this:
MyViewModel model = new ViewModelProvider(getViewLifecycleOwner()).get(MyViewModel.class);
model.getUsers().observe(getViewLifecycleOwner(), users -> {
// update UI
});
Don't feel overwhelmed by this. What it does in reality is relatively simple. The ViewModel survives configuration changes. Meaning if you rotate your phone the loadUsers request won't be invoked again - same with switching between bottom navigation tabs. Of course If the fragment is destroyed, the ViewModel does also get destroyed (the function onCleared is invoekd then).
The LiveData users is just a fancy name for a simple observer. Mutable means that you can set a value, getUsers() returns a non mutable LiveData, this means you can only read its value. When you set a value to a LiveData object, it's subscriber will be notified. You can imagine it like the LiveData is an interface implmented by your Fragment which is using the ViewModel. And this interfaces function is invoked once you have fetched data. More info on dealing with LiveData is explained here you should definitely check it out.
So the ViewModel will invoke loadUsers once you start observing getUsers if the Users have not been loaded yet. If they have been loaded, the current value is returned.
Oh and to add LiveData and ViewModel -> it's explained here :)
Hope this was helpful. I know it is alot but trust me it is worth investing the time!

Fragment listview update from activity

I am pretty new to Android (3 days), but I have a pretty good background in PHP (which may be the cause of my confusion in a Java based environment). I started building an Android app using Android Studio (Beta). I created the default Android Studio activity with the Navigation Drawer Activity. I edited the activity fragment part to look like this:
#Override
public void onNavigationDrawerItemSelected(int position) {
Bundle bundle = new Bundle();
bundle.putStringArrayList("contacts", arr);
bundle.putStringArrayList("messages", messages);
Fragment fragment = null;
switch (position) {
case 0:
fragment = new FriendsFragment();
break;
case 1:
fragment = new ChatsFragment();
break;
case 2:
fragment = new GroupsFragment();
break;
case 3:
fragment = new LogoutFragment();
break;
default:
break;
}
if (fragment != null) {
fragment.setArguments(bundle);
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, fragment).addToBackStack(null).commit();
}
}
As you can see I am passing a Bundle to my Fragments called "messages" and "contacts" when an item is selected in the Navigation Drawer. The "messages" bundle are XMPP messages received by the aSmack library from an OpenFire server. So basically I'm trying to create a XMPP client. When I run the app I can receive the messages in the "ChatsFragment".
Now my problem:
I have to press the "ChatsFragment" item on the drawer to have my messages updated (re-receive the bundle) everytime I feel like there are new messages received from the server. But I want this to be done automatically by the fragment.
First I would like to know if my procedure is correct (Activity listens to server, creates bundle, send bundle to fragment, bundle updates messages on receive**)
** = This part I haven't been able to understand how to implement.
1- If the procedure is correct tell me how I should get the messages to be updated by the fragment through the activity?
2- If this is not the correct way to do things in Android, recommend me a way of doing it.
My code for displaying the messages in fragment:
private void displayListView() {
// Messages array list
List<String> contacts = getArguments().getStringArrayList("messages");
//System.out.println("arr: " + contacts);
//create an ArrayAdaptar from the String Array
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(getActivity(),
R.layout.url_list, contacts);
ListView listView = (ListView) getView().findViewById(R.id.listView);
// Assign adapter to ListView
listView.setAdapter(dataAdapter);
//enables filtering for the contents of the given ListView
listView.setTextFilterEnabled(true);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// Send the URL to the host activity
//mListener.onURLSelected(((TextView) view).getText().toString());
}
});
}
Thanks in advance.

Typically for long running operations in the background, like listening to a server, incoming messages, etc, you need to use Services. You do so by subclassing the Service class in Android.
Now for your problem - the design approach should be that you have a background service listening to incoming messages. Anytime a message is received (an input stream in your socket operator) you should send a "broadcast" an intent that a message was received. A custom broadcast receiver that you create should wait for this broadcast. Within the onReceive() method of this receiver, you should trigger the creation of the bundle and updating your message.
Remember you should always delegate your long running operations in Android to services. That is exactly what they are for.

So basically if you're already listening for new messages to come in your activity, then you must have some kind of callback like onMessageRecieved() or something like that.
If you do, you can then notify your fragment in this way.
Create a field (goes under your class declaration) called curFrag, so something like this:
public class MyActivity extends Activity {
private Fragment curFrag;
//other code...
}
then in the code you posted you would initialize the curFrag there, but you also need to set a tag for the current fragment. This will be based on your case statement. Make some final string variables as tags.
i.e.
public static final String CHATSTAG = "chatstag";
#Override
public void onNavigationDrawerItemSelected(int position) {
Bundle bundle = new Bundle();
bundle.putStringArrayList("contacts", arr);
bundle.putStringArrayList("messages", messages);
Fragment fragment = null;
String tag = null;
switch (position) {
case 0:
tag = FRIENDSTAG;
fragment = new FriendsFragment();
break;
case 1:
tag = CHATSTAG;... and so on through the switch statement.
fragment = new ChatsFragment();
break;
case 2:
fragment = new GroupsFragment();
break;
case 3:
fragment = new LogoutFragment();
break;
default:
break;
}
if (fragment != null) {
fragment.setArguments(bundle);
FragmentManager fragmentManager = getSupportFragmentManager();
//remember to set the tag.
if(tag != null) {
fragmentManager.beginTransaction()
.replace(R.id.container, fragment, tag).addToBackStack(null).commit();
} else {
fragmentManager.beginTransaction()
.replace(R.id.container,fragment,DEFAULTTAG).addToBackStack(null).commit();
}
//new code
curFrag = fragment;
}
}
Now in your activity when a new message comes in, check the tag of the fragment and then if it matches a certain fragment, notify the fragment that new data has come in and retrieve it in the fragment.
public void onMessageRecieved() {
if(curFrag.getTag().equalsIgnoreCase(CHATSTAG)) {
ChatsFragment frag = (ChatsFragment) curFrag;
frag.notifyDataRecieved();
}
}
Once you have a reference to your fragment in the activity, you have access to any public methods in that fragment.
If your fragment cannot access the data on its own, then you'll need to get a reference to the activity and create a method in the activity that returns the new data.
So in your activity:
public String getMessageData() {
String newData = ...//get stuff from server;
return newData;
}
then in your fragment
public void notifyNewMessage() {
try {
MyActivity activity = (MyActivity) getActivity();
} catch (ClassCastException e) {
e.printStackTrace();
} catch (NullPointerException e) {
e.printStackTrace();
}
String message = activity.getMessageData();
//do something with the message.
}
It's not necessarily pretty but it works pretty well. You should also check to make sure your fragments are attached when you do this so that you avoid null exceptions.
Hope this helps!

Android FragmentTransaction() IllegalStateException: Fragment already added

I am trying to show multiple fragments in a FrameLayout container. The basic idea is to use a spinner to select a different fragment to be displayed in the container. I am trying to add them programmatically and for this I have created one xml file for each day of the week which is what I am trying to show.
// Set up the spinner to select days of the week.
Spinner spinner = (Spinner) weekView.findViewById(R.id.day_selecter);
spinner.setOnItemSelectedListener(new OnItemSelectedListener(){
#Override
public void onItemSelected(AdapterView<?> parent, View view,
int pos, long id) {
// For each day of the week, create a new instance of Switches
// get an instance of FragmentTransaction from your Activity
FragmentManager fm = getFragmentManager();
FragmentTransaction fragmentTransaction = fm.beginTransaction();
Fragment frag = fm.findFragmentByTag(Integer.toString(pos));
if(frag == null) {
switch(pos) {
case 0: frag = new mondayFragment();
break;
case 1: frag = new tuesdayFragment();
break;
case 2: frag = new wednesdayFragment();
break;
case 3: frag = new thursdayFragment();
break;
case 4: frag = new fridayFragment();
break;
case 5: frag = new saturdayFragment();
break;
case 6: frag = new sundayFragment();
break;
}
fragmentTransaction.add(R.id.week_program_switches, frag, Integer.toString(pos));
}
else
fragmentTransaction.replace(R.id.week_program_switches, frag, Integer.toString(pos));
fragmentTransaction.commit();
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
The program manages to load the fragment corresponding to the first day of the week, i.e. the mondayFragment into the container. Each fragment contains textboxes and checkboxes so i need to save the view of each fragment loaded. At times the app would allow me to select a different day but the content from the previous fragment gets carried over and it eventually crashes the app with an IllegalStateException error: Day has already been added to fragment transaction. other times, simply selecting a different day in the spinner immediately crashes the app with the same error. I really need your help in this as I'm all out of ideas.
Few Notes:
1. I have not added any fragment statically into any layout. I have seen this to be the cause of many related issues.
2. I originally intended to use a single fragment and create multiple instances in a frameLayout container but i had similar issues of saving the content in each instance.

Checking current opened fragment position while using DrawerLayout

I am using android DrawerLayout from Support Library to show slide menu.I am using a single activity and 5-6 fragments to show them upon selection in DrawerLayout menu.But I have a small problem which is "How do I check which fragment is currently visible so if user selected the menu item which corresponds to already opened fragment. Currently it creating the Fragment again and displaying it which is not good.The function that triggers when clicked on menu item is:
private void selectItem(int position) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
// Locate Position
switch (position) {
case 0:
ft.replace(R.id.content_frame, fragment1);
break;
case 1:
ft.replace(R.id.content_frame, fragment2);
break;
case 2:
ft.replace(R.id.content_frame, fragment3);
break;
}
ft.commit();
mDrawerList.setItemChecked(position, true);
// Close drawer
mDrawerLayout.closeDrawer(mDrawerList);
}
How do I check if the requested fragment is already opened so not to create it again?Is their any method to check this through FragmentManager?

I would add to #Plato's answer.
Check get currently displayed fragment question if you haven't already.
The answer says that when you add the fragment in your transaction, you can use a tag to represent a particular fragment. Something like:
ft.replace(android.R.id.content, fragment, "MY_FRAGMENT");
Later if you want to check if that fragment is visible, you can do something like:
RequestedFragment fragment = (RequestedFragment)getFragmentManager().findFragmentByTag("MY_FRAGMENT"); //"My_FRAGMENT" is its tag
if (fragment.isVisible()) {
// add your code here
}
Hope this helps.

the simplest approach would be to store last used position and compare next time. Just make your selectItem method like:
int lastPosition = -1;
private void selectItem(int position) {
if( position != lastPosition ) {
[ old method body here ]
lastPostion = position;
}
}

Assign different tags to each one of your fragments and call findFragmentByTag() of the FragmentManager to check if each one is already present.
You can also use the findFragmentById() of the FragmentManager for the same purpose and use the ids of your fragments.

If you are absolutely sure that each of fragment1, fragment2, fragment3 cannot be visible at the same time and if you reuse the same fragments (i.e. do not create a new fragment each time you change position) then the method isVisible() from the class Fragment should tell you if that fragment is currently visible.
Your switch should look like:
switch (position) {
case 0:
if(!fragment1.isVisible()) {
ft.replace(R.id.content_frame, fragment1);
}
break;
case 1:
if(!fragment2.isVisible()) {
ft.replace(R.id.content_frame, fragment2);
}
break;
case 2:
if(!fragment3.isVisible()) {
ft.replace(R.id.content_frame, fragment3);
}
break;
}