Develop Reference

Go back to the default fragment

I have a Android app with one activity and two fragments. First fragment (MainFragment) show a list of "items" and second (DetailsFragment) display a item's details (very basic).
On the normal flow, the activity start and show first fragment and the second is shown when a item is clicked.
But the second fragment can be shown directly throught click on a notification (by putting extra arguments to the activity).
String id = getIntent().getStringExtra("id");
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
if (id != null) {
fragment = new DetailsFragment();
Bundle args = new Bundle();
args.putString("id", id);
fragment.setArguments(args);
} else {
fragment = new MainFragment();
}
ft.replace(R.id.main, fragment);
ft.commit();
In the second case, the problem is : How to open MainFragment when clicking back from DetailsFragment ? Actually the app finish because only the second fragment has been created.

First way: Its very simple. You just need to use addToBackStack(null). It will save your desired fragment and when you use backpressed it will open that one.
Do something like this:
if (id != null) {
fragment = new DetailsFragment();
Bundle args = new Bundle();
args.putString("id", id);
fragment.setArguments(args);
ft.replace(R.id.main, fragment);
ft.commit();
} else {
fragment = new MainFragment();
ft.replace(R.id.main, fragment).addToBackStack(null);
ft.commit();
}
Second way: in your DetailsFragment's onResume() method write this code.
#Override
public void onResume() {
super.onResume();
getView().setFocusableInTouchMode(true);
getView().requestFocus();
getView().setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK) {
fragment = new MainFragment();
fragmentManager = getFragmentManager();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.main, fragment);
fragmentTransaction.commit();
return true;
}
return false;
}
});
}

Add the main fragment in the onCreate() of the activity and override the onBackPressed() in the main activity
FragmentTransaction mFragmentTransaction = fragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.frame_container_recharege, fragment);
mFragmentTransaction.commit();
#Override
public void onBackPressed() {
FragmentManager fragmentManager = getSupportFragmentManager();
if (fragmentManager.getBackStackEntryCount() > 1) {
fragmentManager.popBackStack();
} else {
super.onBackPressed();
}
}

This is very common situation in Android, and simply saying you can just add it to backstack. So when user presses back button he will see the previous fragment(MainFragment).
getFragmentManager()
.beginTransaction()
.addToBackStack(yourFragment.getClass().getSimpleName())
.replace(R.example.container, yourFragment)
.commit();
Have a read official Android documentation about the back stack
UPDATE:
If you open DetailsFragment directly(without opening MainFragment) then you should check the back stack, if it is empty then open MainFragment manually. Here is the full code:
if (getSupportFragmentManager().getBackStackEntryCount() == 0) // empty back stack{
getFragmentManager()
.beginTransaction()
.replace(R.example.container, MainFragment)
.commit();
}

You can use something like this on your back press or back button clicked
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
fragment = new MainFragment();
ft.replace(R.id.fragment_container, frag);
ft.commit();

add fragment like this
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
ft.replace(containerId, fragment);
ft.addToBackStack(backStateName);
ft.commit();
and in your activity backpress put this
getSupportFragmentManager().popBackStack();

How to check if the fragment exists

I am trying to talk to the fragments from activity.
Here in my MainActivity I am adding multiple fragments ok so for fine.
My main requirement is I don't want to add if fragment is already added.
So how can we check this condition?
Please help me some one.
code:-
private void intializingFragments(Fragment fragment) {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
private View.OnClickListener intialization() {
return new View.OnClickListener() {
#Override
public void onClick(View v) {
int getId = v.getId();
if (getId == R.id.first) {
intializingFragments(new Fragment1());
} else if (getId == R.id.second) {
intializingFragments(new Fragment2());
} else if (getId == R.id.third) {
intializingFragments(new Fragment3());
}
}
};
}

You can use findFragmentByTag() or findFragmentById() functions to get a fragment. If mentioned methods are returning null then that fragment does not exist.
Fragment fragmentA = fragmentManager.findFragmentByTag("frag1");
if (fragmentA == null) {
// not exist
} else {
// fragment exist
}
for example:- http://wiki.workassis.com/android-load-two-fragments-in-one-framelayout/

You may find fragment in fragmentmanager:
List<Fragment> frags = getSupportFragmentManager().getFragments();
for (Fragment f : frags) {
<find what you want>...
}
Or you may add fragment with tag:
getSupportFragmentManager()
.beginTransaction()
.add(R.id.frame, new MyFragment(), "frag1")
.commit();
And find by tag
getSupportFragmentManager().findFragmentByTag("frag1");

FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction transaction = fragmentManager.beginTransaction();
Fragment topFragment = fragmentManager.findFragmentById(R.id.container);
FragmentA fragmentA = new FragmentA();
if(topFragment!= null)
{
transaction.remove(topFragment);
transaction.add(R.id.container, fragmentA, "FA");
transaction.commit();
}
else
{
transaction.add(R.id.container, fragmentA, "FA");
transaction.commit();
}
try this
private void intializingFragments(Fragment fragment) {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment topFragment = fragmentManager.findFragmentById(R.id.container);
if(topFragment!= null)
{
fragmentTransaction.remove(topFragment);
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
else
{
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
}

How to check whether a fragment exists, without knowing its resource ID or tag:
// MyActivity.kt
val exists: Boolean = supportFragmentManager
.fragments
.filterIsInstance<MyFragment>()
.isNotEmpty()

There are many ways by which you can track the last added fragment. The simplest one is by finding the tag within fragment manager. Here is the sample code of it:
public boolean isFragmentPresent(String tag) {
Fragment frag = getSupportFragmentManager().findFragmentByTag(tag);
if (frag instanceof HomeFragment) {
return true;
} else
return false;
}
Alternatively, you can use your own variable to check whether the last added fragment is the same as the current fragment. Here is the sample code for it:
public boolean isCurrentFragment(Fragment fragment) {
if (fragment instanceof HomeFragment && getLastAddedFragment() instanceof HomeFragment) { // getLastAddedFragment() is a method which return the last added fragment instance
return true;
} else
return false;
}
And you can use it like:
if (isCurrentFragment(new HomeFragment())) {
// Last added Fragment is the HomeFragment
}

You can go for popBackStack Pop the last fragment transition from the manager's fragment back stack. If there is nothing to pop, false is returned. enter link description here

You can get the list of previously added fragments from the fragment manager. Then just check whether the list contains your fragment object or not.
getSupportFragmentManager().getFragments().contains(yourFragment);

This one doesn't work
!getSupportFragmentManager().getFragments().contains(fragment)
This works for me
getSupportFragmentManager().findFragmentByTag(fragment::class.java.getSimpleName()) == null

Back Button on fragment not working

I have a fragment activity from where i can start my fragments which contain a viewpager. In my fragment activity I have added this piece of code.
fragment = new ItemPagerFragment();
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.replace(R.id.content_frame, fragment);
transaction.addToBackStack(null);
transaction.commit();
Now when I press back button only blank screen appears and it does not lead me to my fragment activity.
What wrong i might be doing?

Use this in activity that holds fragment.
#Override
public void onBackPressed() {
if (fragmentManager.getBackStackEntryCount() > 1) {
fragmentManager.popBackStack();
} else
finish();
}

Try this way,
// Create new fragment and transaction
Fragment newFragment = new ItemPagerFragment();
// consider using Java coding conventions (upper first char class names!!!)
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(R.id.content_frame, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
Modify your code
#Override
public void onBackPressed() {
if(some condition) {
// do something
} else {
super.onBackPressed();
}
}
Please follow this link
Handling back button press Inside Fragments

You have to tell to the fragment manager that the back button was pressed. Override onBackPressed on your Activity
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() == 0) {
super.onBackPressed();
} else {
getFragmentManager().popBackStack();
}
}

private void changeFragment (Fragment fragment){
String backStackName = fragment.getClass().getName();
FragmentManager manager = getSupportFragmentManager();
boolean fragmentPopped = manager.popBackStackImmediate (backStackName, 0);
if (!fragmentPopped){ //fragment not in back stack, create it.
FragmentTransaction ft = manager.beginTransaction();
ft.replace(R.id.content_frame, fragment);
ft.addToBackStack(backStackName );
ft.commit();
}
}

While launching fragment assign a TAG to each fragment.When you want to back press check the existence of an fragment using assigned TAG name and then do corresponding action.for example:
private final static String TAG_FRAGMENT = "TAG_FRAGMENT";
//when want to add fragment to view
private void showFragment() {
final Myfragment fragment = new MyFragment();
final FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment, fragment, TAG_FRAGMENT);
transaction.addToBackStack(null);
transaction.commit();
}
//in activity back pressed check the existence of fragment by TAG
#Override
public void onBackPressed() {
final Myfragment fragment = (Myfragment) getSupportFragmentManager().findFragmentByTag(TAG_FRAGMENT);
if (fragment.allowBackPressed()) { // and then you define a method allowBackPressed with the logic to allow back pressed or not
super.onBackPressed();
}
}

Back Stack fragment blank onbackpressed

i have 2 fragments, when i replace the second fragment and press the back button at that time my first fragment shows blank,here is my code
Fragment fragment = new MovieDetails();
Bundle args = new Bundle();
args.putString("background", item.getBackg());
args.putString("thumb", item.getThumb());
args.putString("id", item.getCode());
fragment.setArguments(args);
String backStateName = fragment.getClass().getName();
boolean fragmentPopped = getActivity()
.getSupportFragmentManager().popBackStackImmediate(
backStateName, 0);
if (!fragmentPopped) { // fragment not in back stack, create it.
FragmentTransaction ft = getActivity()
.getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, fragment);
ft.addToBackStack("TAG");
ft.commit();
}
getActivity().getSupportFragmentManager().beginTransaction()
.replace(R.id.content_frame, fragment).commit();

You can do this
private void showFragment() {
final Myfragment fragment = new MyFragment();
final FragmentTransaction transaction =
getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment, fragment, TAG_FRAGMENT);
transaction.addToBackStack(null);
transaction.commit();
}
#Override
public void onBackPressed() {
final Myfragment fragment = (Myfragment)getSupportFragmentManager().findFragmentByTag(TAG_FRAGMENT);
if (fragment.allowBackPressed()) {
super.onBackPressed();
}

This probably isn't your problem, but it was mine: I'd over-ridden onSaveInstanceState() and forgotten to call through to super. This resulted in a blank fragment after pressing 'back', almost certainly because super.onSaveInstanceState() is where the fragment stack gets saved.

Fragment dismiss after tap on Back button

I have two Fragments - FragmentA and FragmentB.
I try to show FragmentB from FragmentA.
FragmentB fragmentB = new FragmentB();
MainActivity activity = (MainActivity) getActivity();
int fragmentContainer = activity.getFragmentContainer();
FragmentTransaction fragmentTransaction = activity.getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(fragmentContainer, fragmentB);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
MainActivity
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
fragmentA = new FragmentA(getSupportFragmentManager());
//...
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(FRAGMENT_CONTAINER,fragmentA);
fragmentTransaction.commit();
}
FragmentB is showed, but when i click on back button i have a next situation - FragmentB was dismissed, but FragmentA not showed.
Why this happens and what i need to edit to get a correct result?

getActivity().getChildFragmentManager().beginTransaction();
use this it may be works inside fragmentB

Thanks to New Developer for provided link.
All that we need it's just add a
#Override
public void onBackPressed(){
if (getSupportFragmentManager().getBackStackEntryCount() == 1){
finish();
}
else {
super.onBackPressed();
}
}
and
private void replaceFragment (Fragment fragment){
String backStateName = fragment.getClass().getName();
String fragmentTag = backStateName;
FragmentManager manager = getSupportFragmentManager();
boolean fragmentPopped = manager.popBackStackImmediate (backStateName, 0);
if (!fragmentPopped && manager.findFragmentByTag(fragmentTag) == null){ //fragment not in back stack, create it.
FragmentTransaction ft = manager.beginTransaction();
ft.replace(R.id.content_frame, fragment, fragmentTag);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.addToBackStack(backStateName);
ft.commit();
}
}
and manage fragments in activity.
So if we need a swap fragments just call :
replaceFragment(new MySwappingFragment());