Develop Reference

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.

Can not add Fragment

I've been stuck on this for a while now and will appreciate any guidance on this. Also not sure if my title is accurate. Inside my adapter I create a new fragment:
Adapter code:
cardAdoptDetailsFrag nextFrag = new cardAdoptDetailsFrag();
android.support.v4.app.Fragment callingFrag = ((FragmentActivity)context).getSupportFragmentManager().findFragmentByTag("TagFeedFragment");
FragmentTransaction ft = ((FragmentActivity)context).getSupportFragmentManager().beginTransaction();
ft.hide(callingFrag);
ft.add(R.id.fram, nextFrag,"cardAdoptDetailsFrag");
ft.addToBackStack("TagFeedFragment");
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.commit();
Then inside my Main Activity where I manage all the fragments, I'm trying to check if the "cardAdoptDetailsFrag" isAdded. For some reason I cannot do it as per the below.
Get Fragment by tag. The below is where it fails with null object reference.
Fragment frag = getSupportFragmentManager().findFragmentByTag("cardAdoptDetailsFrag");
Log.d(TAG, "Check if added: "+frag.isAdded());
Now I know I can just add it inside a method and do a null check and return a boolean, but I know I'm doing something wrong here. Because with my other fragments the isAdded and remove works, but they get initiated inside the Main Activity where "cardAdoptDetailsFrag" gets initiated inside the adapter.
Example of Main Activity:
public class MainActivity extends AppCompatActivity implements adoptFeedFragment.OnFragmentInteractionListener,
lostAndFoundFragment.OnFragmentInteractionListener,
servicesFragment.OnFragmentInteractionListener,
userMenuFragment.OnFragmentInteractionListener,
showUserAdoptPostsFrag.OnFragmentInteractionListener{
adoptFeedFragment adoptFeedFragment;
lostAndFoundFragment lostAndFoundFragment;
servicesFragment servicesFragment;
userMenuFragment userMenuFragment;
....
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
adoptFeedFragment = new adoptFeedFragment();
lostAndFoundFragment = new lostAndFoundFragment();
servicesFragment = new servicesFragment();
userMenuFragment = new userMenuFragment();
....
//Here I can do for example:
adoptFeedFragment.isAdded(); //Will simply return a boolean.
//Or I can do a remove:
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.remove(adoptFeedFragment);
//But I cannot do the below:
Fragment frag = getSupportFragmentManager().findFragmentByTag("cardAdoptDetailsFrag");
Log.d(TAG, "frag.isAdded(): "+frag.isAdded());
*****Edited Post. Ok lets say the frag is added. Why can I not remove it using the below.
public boolean isAdoptDetailsFragAdded() {
Fragment frag = getSupportFragmentManager().findFragmentByTag("cardAdoptDetailsFrag");
if(frag == null){
return false;
} else {
return true;
}
}
public Fragment getAdoptDetailsFrag() {
return getSupportFragmentManager().findFragmentByTag("cardAdoptDetailsFrag");
}
//I'm unable to remove the fragment using the below:
Log.d(TAG, "showFeedFragment: "+isAdoptDetailsFragAdded()); <--returns true
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
if(isAdoptDetailsFragAdded()) {
ft.remove(getAdoptDetailsFrag());
}
ft.commit();
//Now I check again wether it is still added. And still returns true even though I just removed it.
Log.d(TAG, "showFeedFragment: "+isAdoptDetailsFragAdded()); <-- Still returns true.
}

This is my fragment adding or replacing method which i am using in 13 projects.
You can use it and get rid of managing fragments.
/**
* replace or add fragment to the container
*
* #param fragment pass android.support.v4.app.Fragment
* #param bundle pass your extra bundle if any
* #param popBackStack if true it will clear back stack
* #param findInStack if true it will load old fragment if found
*/
public void replaceFragment(Fragment fragment, #Nullable Bundle bundle, boolean popBackStack, boolean findInStack) {
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
String tag = fragment.getClass().getName();
Fragment parentFragment;
if (findInStack && fm.findFragmentByTag(tag) != null) {
parentFragment = fm.findFragmentByTag(tag);
} else {
parentFragment = fragment;
}
// if user passes the #bundle in not null, then can be added to the fragment
if (bundle != null)
parentFragment.setArguments(bundle);
else parentFragment.setArguments(null);
// this is for the very first fragment not to be added into the back stack.
if (popBackStack) {
fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
} else {
ft.addToBackStack(parentFragment.getClass().getName() + "");
}
ft.replace(R.id.main_frame_container, parentFragment, tag);
ft.commit();
fm.executePendingTransactions();
}
Here R.id.main_frame_container is FrameLayout in activity layout on which fragment is placed.

Here findFragmentByTag() is returning null when you do getSupportFragmentManager().findFragmentByTag("cardAdoptDetailsFrag").
findFragmentByTag() will return null in two cases.
If fragment cardAdoptDetailsFrag is not yet attached to view (you did not call add or replace for this fragment)
You added that fragment, but you are using different TAG, while searching that fragment.
Make sure if non of the case in your problem.
Now the solution is, you can modify your logic, like
Fragment frag = getSupportFragmentManager().findFragmentByTag("cardAdoptDetailsFrag");
if (frag != null && frag.isAdded()) {
// Do you task. Fragment is added
} else {
// Fragment is not added yet
}

I did not went through the long post but I read only this part.
Now I check again wether it is still added. And still returns true even though I just removed it.
And the reason behind that is FragmentTransaction.commit is not synchronous.
Read the docs for commit method:
*Schedules a commit of this transaction. The commit does
* not happen immediately; it will be scheduled as work on the main thread
* to be done the next time that thread is ready.*
If you need that to be synchronous, use commitNow instead.

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.

Fragment Replacement Techniques

I have three fragments which are bound to Tabs as you swipe from TabA to TabB to TabC and it respectively loads FragA, FragB and FragC using ViewPager(Hope you understand this part). This swipe Tabs works just fine but I have a few fixed buttons attached to the bottom of the layout and when each button is clicked i want to load a new fragment to replace any of the Fragment A, B or C. The replacement works fine but when i return to the replaced/previous Fragment all the UI components on that layout completely disappears and it does not indicate if it has been paused, stopped or destroyed. Heres the Code:
Replacing previous Fragment Code:
if(actionBar.isShowing())
{
actionBar.hide();
}
FragmentManager fms = getSupportFragmentManager();
FragmentTransaction fts = fms.beginTransaction();
search s = new search();
if(getCurrentDisplayFragment() == Type1)
{
setcurrentItem(viewPager.getCurrentItem());
Fragment frgs = mAdapter.getItem(viewPager.getCurrentItem());
viewPager.removeViewAt(viewPager.getCurrentItem());
frgs.setUserVisibleHint(false);
Log.i("if say", "Not Responding");
}
fts.replace(R.id.hoster, s);
fts.addToBackStack("search");
fts.commit();
setCurrentDisplayFragment(s,Type2);
The setCurrentDisplayFragment(s,Type2); i built that code to help indicate which fragment is being replaced and what measures to take. S is a Fragment and Type2 is a string
Thus when the back button is pressed i want to return back to any of the Fragments A, B or C that was previously replaced.
Here is the code:
#Override
public void onBackPressed() {
// TODO Auto-generated method stub
//super.onBackPressed();
Log.i("event in back","I have been presssed ");
if(getCurrentDisplayFragment() == Type2)
{
actionBar.show();
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
fm.popBackStack();
ft.remove(getCurrentDisplayFragment(Type2));
ft.commit();
viewPager.setCurrentItem(getcurrentItem());
actionBar.setSelectedNavigationItem(getcurrentItem());
Fragment frags = mAdapter.getItem(viewPager.getCurrentItem());
frags.setUserVisibleHint(true);
setCurrentDisplayFragment(frags, Type1);
}
else
{
}
}
Though some variable names and method declaration are not shown but you should get the picture of what am doing because all declarations have been done. its just The Replacement and retaining of their UI states thats giving me a problem.

Why are you complicating this so much? If you want to replace any of the fragments in the view pager, then just replace the view pager. It would be a lot easier if you would have a fragment holding the view pager with the tabs and when the bottom buttons are pressed, you just replace the fragment holding the view pager with the new fragment. In this way you won't need to do anything when the back button will be pressed.