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am creating multiple fragment app, which require easy changing of fragment tabs, whose BackStack entry must be kept. On user click fragment must be pop up immediate. I think reordering BackStack is the best option. Do anyone know how to reorder BackStack ?
I have 5 fragments A,B,C,D,E. if user open fragment like A ---> B ---> C ---> D ---> E . using default back stack,back key it works fine. But when user opens A ---> B ---> C ---> D ---> E ---> B. After this if user click back, default back stack will goes to A.
There is no api for this usecase, but there are other means to do so:
Example
FragmentBackStackModifyActivity
use non-swipable viewpager and on addOnPageChangeListener create arraylist and save all pages that opened. onBackPressed will compare arraylist and show pages.
The user follows the path A ---> B ---> C ---> D ---> E then he wants to come to B. So what you should do is:
check if B is already in the back stack or not.
If it is there, then popBackStackImmediate to return to B
If it is not there, then add the fragment B normally.
So replace fragment should be something like this:
public void replaceFragment(Fragment fragment) {
String fragmentTag = fragment.getClass().getCanonicalName(); //unique name for the fragment, which will be used as tag.
FragmentManager fragmentManager = getSupportFragmentManager();
boolean isPopped = fragmentManager.popBackStackImmediate(fragmentTag, 0); // trying to return to the previous state of B if it exists.
if (!isPopped && fragmentManager.findFragmentByTag(fragmentTag) == null){ // fragment is not in the backstack, so create it.
FragmentTransaction ft = fragmentManager.beginTransaction();
ft.replace(R.id.frame_layout, fragment, fragmentTag);
ft.addToBackStack(fragmentTag);
ft.commit();
}
}
Remember, this will return to the previous state of B.
TIP: Since you don't want two instances of any fragment, So try to create a singleton instance of them. Because, if you are creating a new instance of the fragment and that fragment already exists in the back stack then the new instance will be ignored (because you are returning to the previous state).
You Can Try this...
onBackpressed
#Override
public void onBackPressed() {
Fragment f = getSupportFragmentManager().findFragmentById(R.id.frame_container);
if (f instanceof FragmentE)
{
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.popBackStack(fragmentManager.getBackStackEntryAt(fragmentManager.getBackStackEntryCount()-1).getId(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
} else if (f instanceof FragmentD) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.popBackStack(fragmentManager.getBackStackEntryAt(fragmentManager.getBackStackEntryCount()-2).getId(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
else if (f instanceof FragmentC) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.popBackStack(fragmentManager.getBackStackEntryAt(fragmentManager.getBackStackEntryCount()-3).getId(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
else if (f instanceof FragmentB) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.popBackStack(fragmentManager.getBackStackEntryAt(fragmentManager.getBackStackEntryCount()-4).getId(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
else
{
super.onBackPressed();
}
}
for back remove stack
final android.app.FragmentManager fm = getFragmentManager();
fm.addOnBackStackChangedListener(new android.app.FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
if (getSupportFragmentManager().getBackStackEntryCount() ==0) {
// dLayout.closeDrawers();
finish();
}
else
{
// dLayout.closeDrawers();
}
}
});
May be call addToBackstack() only when the fragment is not added before
Suppose as in your case when user is in Fragment E and when user calls Fragment B check if the Fragment B is already added in back stack
if yes, Then dont call addToBackstack for that FragmentTransaction.
else ,call addToBackstack()
check my sample code:
private void addFragment (Fragment fragment){
boolean isFragment=false;
String backStateName = fragment.getClass().getName();
FragmentManager fm = getFragmentManager();
for(int entry = 0; entry < fm.getBackStackEntryCount(); entry++){
Log.i(TAG, "Found fragment: " + fm.getBackStackEntryAt(entry).getId());
if(fm.getBackStackEntryAt(entry).getId().equalsIgnoreCase(FragmentB))// check if fragment is in back stack
{
isFragment=true;
}
}
if (!isFragment){ //fragment added to back stack, create it.
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragmentContainer, FragmentB).addToBackStack(FragmentB).commit();
}else {//else dont call addToBackStack()
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragmentContainer, FragmentB).commit();
}
}
Just place this code in your MainActivity
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
//super.onBackPressed();
if (getFragmentManager().getBackStackEntryCount() == 1) {
finish();
}
getFragmentManager().popBackStack();
}
}
Here getFragmentManager().getBackStackEntryCount() == 0 will checks that whether the stack entry is at 0 or not, if it's on 0 then the Activity will be finished.
In your case A --> B --> C --> D --> E --> B
A will be on 0,
B will be on 1,
C on 2,
D on 3,
E on 4,
B on 5
So when you click on back, the if condition will checks that the backstack count is on 0.
How is it possible to go back to the last Activity one has been in from a Fragment? Let's assume we've Activity A and Fragment A. I launch Fragment A from Activity A, and now I want to go back to Fragment A. When I press on the back button on my phone it closes the app.
I launch the fragment by using the FragmentManager:
Fragment fragment = new Kontakt();
getFragmentManager().beginTransaction()
.add(R.id.kontaktfrag, fragment)
.commit();
Is the solution; popBackStackImmediate() or addToBackStack() ?
Firstly try addToBackStack when adding your fragment.
then you need to override your onBackPressed function of your activity, for example:
#Override
public void onBackPressed() {
if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
getSupportFragmentManager().popBackStackImmediate();
} else {
super.onBackPressed();
}
}
I tried myself and it worked.
try adding
getFragmentManager()
.beginTransaction()
.addToBackStack("")
.commit();
or just add .addToBackStack("") before .commit();
here is the code in your case,
Fragment fragment = new Kontakt();
getFragmentManager().beginTransaction()
.add(R.id.kontaktfrag, fragment)
.addToBackStack("")
.commit();
I have an application with navigation drawer. when i start the application, what i have on main screen (screen A) is "hello world" and then when i select an item from navigation drawer, i load a fragment and get "new hello world" and then again when i select an item from navigation drawer, i load a fragment and get "hello universe". But since this is all happening via 1 single fragment, when i press the device back button i should get previous fragment like below:
"hello universe" >press back> "new hello world" >press back> "hello world"
how do i handle this ?
NOTE:
while changing the fragment i have tried
fragmentManager.beginTransaction().replace(R.id.mainContent, fragment).commit();
then i changed to :
fragmentManager.beginTransaction().add(R.id.mainContent, fragment).addToBackStack("tag").commit();
but nothing worked. The app exits on back button press.
Is it due to the same fragment getting replaced by another content again and again?
The second approach you tried is correct.Try to call popBackStack() on BackPressed() by overriding onBackPressed() method.
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 0) {
getFragmentManager().popBackStack();
} else if (getFragmentManager().getBackStackEntryCount() == 0) {
super.onBackPressed();
}
}
I think you need to add the fragment to the backstack by calling addToBackStack, something like this:
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
if (fragmentManager.findFragmentByTag("MainFragment") == null) {
fragmentTransaction.add(R.id.content_frame, fragment, "MainFragment");
} else {
fragmentTransaction.replace(R.id.content_frame, fragment, "MainFragment");
fragmentTransaction.addToBackStack("Fragment" + position);
}
fragmentTransaction.commit();
and the override OnBackPressed():
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 0 ){
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}
use methods addToBackStack and popBackStack in order to handle back button for fragments here is sample
ft.replace(R.id.simple_fragment, newFragment);
ft.addToBackStack("tag");
ft.commit();
and on back button
FragmentManager fm = getSupportFragmentManager();
if (fm.getBackStackEntryCount() > 0) {
fm.popBackStack();
}
I have an Activity and many fragments inflated in same FrameLayout
<FrameLayout
android:id="#+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
example: mainActivity > any fragment (press back button) > activity is blank.
In onCreate:
layout = (FrameLayout)findViewById(R.id.content_frame);
layout.setVisibility(View.GONE);
When I start a fragment:
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, profileFragment);
ft.addToBackStack(null);
ft.commit();
layout.setVisibility(View.VISIBLE);
I suppose I need to make the frameLayout's visibility GONE again on back pressed, but how do I do this?
I tried onBackPressed and set layout.setVisibility(View.GONE); but I cannot go back through fragments, as I go directly to main page.
If you have more than one fragment been used in the activity or even if you have only one fragment then the first fragment should not have addToBackStack defined. Since this allows back navigation and prior to this fragment the empty activity layout will be displayed.
// fragmentTransaction.addToBackStack() // dont include this for your first fragment.
But for the other fragment you need to have this defined otherwise the back will not navigate to earlier screen (fragment) instead the application might shutdown.
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
}
else {
int fragments = getSupportFragmentManager().getBackStackEntryCount();
if (fragments == 1) {
finish();
} else if (getFragmentManager().getBackStackEntryCount() > 1) {
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}
}
To add a fragment
getSupportFragmentManager().beginTransaction()
.replace(R.id.layout_main, dashboardFragment, getString(R.string.title_dashboard))
.addToBackStack(getString(R.string.title_dashboard))
.commit();
Sorry for the late response.
You don't have to add ft.addToBackStack(null); while adding first fragment.
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, profileFragment);
// ft.addToBackStack(null); --remove this line.
ft.commit();
// ... rest of code
If you want to track by the fragments you should override the onBackPressed method, like this
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() == 1) {
finish();
} else {
super.onBackPressed();
}
}
You can override onBackPressed and check to see if there is anything on the backstack.
#Override
public void onBackPressed() {
int fragments = getFragmentManager().getBackStackEntryCount();
if (fragments == 1) {
// make layout invisible since last fragment will be removed
}
super.onBackPressed();
}
Just don't add the first fragment to back stack
Here is the Kotlin code that worked for me.
val ft = supportFragmentManager.beginTransaction().replace(container, frag)
if (!supportFragmentManager.fragments.isEmpty()) ft.addToBackStack(null)
ft.commit()
On a recent personal project, I solved this by not calling addToBackStack if the stack is empty.
// don't add the first fragment to the backstack
// otherwise, pressing back on that fragment will result in a blank screen
if (fragmentManager.getFragments() != null) {
transaction.addToBackStack(tag);
}
Here's my full implementation:
String tag = String.valueOf(mCurrentSectionId);
FragmentManager fragmentManager = mActivity.getSupportFragmentManager();
Fragment fragment = fragmentManager.findFragmentByTag(tag);
if (fragment != null) {
// if the fragment exists then no need to create it, just pop back to it so
// that repeatedly toggling between fragments doesn't create a giant stack
fragmentManager.popBackStackImmediate(tag, 0);
} else {
// at this point, popping back to that fragment didn't happen
// So create a new one and then show it
fragment = createFragmentForSection(mCurrentSectionId);
FragmentTransaction transaction = fragmentManager.beginTransaction()
.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
.replace(R.id.main_content, fragment, tag);
// don't add the first fragment to the backstack
// otherwise, pressing back on that fragment will result in a blank screen
if (fragmentManager.getFragments() != null) {
transaction.addToBackStack(tag);
}
transaction.commit();
}
irscomp's solution works if you want to end activity when back button is pressed on first fragment. But if you want to track all fragments, and go back from one to another in back order, you add all fragments to stack with:
ft.addToBackStack(null);
and then, add this to the end of onCreate() to avoid blank screen in last back pressed; you can use getSupportFragmentManager() or getFragmentManager() depending on your API:
FragmentManager fm = getSupportFragmentManager();
fm.addOnBackStackChangedListener(new OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
if(getSupportFragmentManager().getBackStackEntryCount() == 0) finish();
}
});
Final words: I don't suggest you to use this solution, because if you go from fragment1 to fragment 2 and vice versa 10 times, when you press back button 10 times it will do it in back order which users will not want it.
Almost same as Goodlife's answer, but in Xamarin.Android way:
Load fragment (I wrote helper method for that, but it's not necessary):
public void LoadFragment(Activity activity, Fragment fragment, string fragmentTitle = "")
{
var fragmentManager = activity.FragmentManager;
var fragmentTransaction = fragmentManager.BeginTransaction();
fragmentTransaction.Replace(Resource.Id.mainContainer, fragment);
fragmentTransaction.AddToBackStack(fragmentTitle);
fragmentTransaction.Commit();
}
Back button (in MainActivity):
public override void OnBackPressed()
{
if (isNavDrawerOpen()) drawerLayout.CloseDrawers();
else
{
var backStackEntryCount = FragmentManager.BackStackEntryCount;
if (backStackEntryCount == 1) Finish();
else if (backStackEntryCount > 1) FragmentManager.PopBackStack();
else base.OnBackPressed();
}
}
And isNavDrawerOpen method:
bool isNavDrawerOpen()
{
return drawerLayout != null && drawerLayout.IsDrawerOpen(Android.Support.V4.View.GravityCompat.Start);
}
I still could not fix the issue through getBackStackEntryCount() and I solved my issue by making the main page a fragment too, so in the end I have an activity with a FrameLayout only; and all other fragments including the main page I inflate into that layout. This solved my issue.
I had the same problem when dealing with Firebase's Ui Login screen. When back button was pressed it left a blank screen.
To solve the problem I just called finish() in my onStop() method for said Activity. Worked like a charm.
If you have scenario like me where a list fragment opens another details fragment, and on back press you first need to show the list fragment and then get out the whole activity then, addToBackStack for all the fragment transactions.
and then on the activity, do like this (courtesy: #JRomero's answer, #MSaudi's comment)
#Override
public void onBackPressed() {
int fragments = getFragmentManager().getBackStackEntryCount();
if (fragments == 1) {
// make layout invisible since last fragment will be removed
}
super.onBackPressed();
}
Just Comment or Remove transaction.addToBackStack(null) in your code.Below is code to change fragment in kotlin.
fun ChangeFragment(activity: MainActivity, fragment: Fragment) {
val transaction: FragmentTransaction =
activity.getSupportFragmentManager().beginTransaction()
transaction.replace(R.id.tabLayoutContainer, fragment)
transaction.commit()
}
Say I have an activity that has fragments added programmatically:
private void animateToFragment(Fragment newFragment, String tag) {
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.fragment_container, newFragment, tag);
ft.addToBackStack(null);
ft.commit();
}
What is the best way to return to the previous fragment that was visible?
I found Trigger back-button functionality on button click in Android but I'm thinking simulating a back key event isn't the right way to go about it (and I can't get it to work either):
dispatchKeyEvent(new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_BACK));
Calling finish() just closes the activity which I'm not interested in.
Is there a better way to go about this?
Look at the getFragmentManager().popBackStack() methods (there are several to choose from)
http://developer.android.com/reference/android/app/FragmentManager.html#popBackStack()
To elaborate on the other answers provided, this is my solution (placed in an Activity):
#Override
public void onBackPressed(){
FragmentManager fm = getFragmentManager();
if (fm.getBackStackEntryCount() > 0) {
Log.i("MainActivity", "popping backstack");
fm.popBackStack();
} else {
Log.i("MainActivity", "nothing on backstack, calling super");
super.onBackPressed();
}
}
When we are updating/add the fragments,
Should Include the .addToBackStack().
getSupportFragmentManager().beginTransaction()
.add(detailFragment, "detail") // Add this transaction to the back stack (name is an optional name for this back stack state, or null).
.addToBackStack(null)
.commit();
After that if we give the getFragments.popBackStackImmediate() will return true if we add/update the fragments, and move back to the current screen.
Android Navigation architecture component.
The following code works for me:
findNavController().popBackStack()
These answers does not work if i don't have addToBackStack() added to my fragment transaction but, you can use:
getActivity().onBackPressed();
from your any fragment to go back one step;
Add those line to your onBackPressed() Method. popBackStackImmediate() method will get you back to the previous fragment if you have any fragment on back stack
`
if(getFragmentManager().getBackStackEntryCount() > 0){
getFragmentManager().popBackStackImmediate();
}
else{
super.onBackPressed();
}
`
This solution works perfectly for bottom bar based fragment navigation when you want to close the app when back pressed in primary fragment.
On the other hand when you are opening the secondary fragment (fragment in fragment) which is defined as "DetailedPizza" in my code it will return the previous state of primary fragment. Cheers !
Inside activities on back pressed put this:
Fragment home = getSupportFragmentManager().findFragmentByTag("DetailedPizza");
if (home instanceof FragmentDetailedPizza && home.isVisible()) {
if (getFragmentManager().getBackStackEntryCount() != 0) {
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
} else {
//Primary fragment
moveTaskToBack(true);
}
And launch the other fragment like this:
Fragment someFragment = new FragmentDetailedPizza();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.container_body, someFragment, "DetailedPizza");
transaction.addToBackStack("DetailedPizza");
transaction.commit();
Kotlin Answer
First, call Fragment Manager.
After, to use onBackPressed()
method.
Coding in Android Studio 4.0 with Kotlin:
fragmentManager?.popBackStack()
Programmatically go back to the previous fragment using following code.
if ( getFragmentManager().getBackStackEntryCount() > 0)
{
getFragmentManager().popBackStack();
return;
}
super.onBackPressed();
To make that fragment come again, just add that fragment to backstack which you want to come on back pressed, Eg:
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Fragment fragment = new LoginFragment();
//replacing the fragment
if (fragment != null) {
FragmentTransaction ft = ((FragmentActivity)getContext()).getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, fragment);
ft.addToBackStack("SignupFragment");
ft.commit();
}
}
});
In the above case, I am opening LoginFragment when Button button is pressed, right now the user is in SignupFragment. So if addToBackStack(TAG) is called, where TAG = "SignupFragment", then when back button is pressed in LoginFragment, we come back to SignUpFragment.
Happy Coding!
By adding fragment_tran.addToBackStack(null) on last fragment, I am able to do come back on last fragment.
adding new fragment:
view.findViewById(R.id.changepass).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.container, new ChangePassword());
transaction.addToBackStack(null);
transaction.commit();
}
});
Following Kotlin code useful to me
1. Added in Simple Activity class with multiple fragments used
override fun onBackPressed() {
if (supportFragmentManager.backStackEntryCount > 0) {
Log.i(TAG, "=============onBackPressed - Popping backstack====")
supportFragmentManager.popBackStack()
} else {
Log.i(TAG, "=============onBackPressed called because nothing on backstack====")
super.onBackPressed()
}
}
2. Added in BottomNavigationView Activity class with multiple fragments used
override fun onBackPressed() {
Log.e(TAG, "=============onBackPressed")
val navController = findNavController(R.id.nav_host_fragment)
when (navController.currentDestination!!.id) {
R.id.navigation_comments, R.id.navigation_my_posts -> {
menuItemPosition = 0
navController.navigate(R.id.navigation_home)
Log.i(TAG, "=============onBackPressed - Popping backstack with First fragment ====")
}
else -> {
Log.i(TAG, "=============onBackPressed called because nothing on backstack====")
super.onBackPressed()
}
}
}
I came here looking or the same idea, and in the meantime i came up with own, which I believe is not that bad and works if with ViewPager.
So what I did, is to override the onBackPressed method in the parent activity that holds the viewPager, and set it to always go back minus 1 position until it reaches the first fragment, then closes the activity.
#Override
public void onBackPressed() {
if(viewPager.getCurrentItem()>0){
viewPager.setCurrentItem(viewPager.getCurrentItem()-1);
} else {
super.onBackPressed();
this.close();
}
}
private void close(){
this.finish();
}
This might have a downfalls, like it only goes back one way left each time, so it might not work great if there are tabs and you switch positions with fragments skipped, ( going from 0 to 2, and then pressing back would put you on 1, instead of 0)
For my case tho, with 2 fragments in viewPager without tabs, it does the job nicely.
getActivity().getSupportFragmentManager().popBackStackImmediate();
OR
getActivity().onBackPressed();
Try below code:
#Override
public void onBackPressed() {
Fragment myFragment = getSupportFragmentManager().findFragmentById(R.id.container);
if (myFragment != null && myFragment instanceof StepOneFragment) {
finish();
} else {
if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
getSupportFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}
}