get the latest fragment in backstack

Question

How can I get the latest fragment instance added in backstack  if I do not know the fragment tag  amp  id    FragmentManager fragManager   activity getSupportFragmentManager    FragmentTransaction fragTransacion   fragMgr beginTransaction          After add   replace fragments     some of the fragments are add to backstack   some are not         HERE  How can I get the latest added fragment from backstack

User · Answer

I personnaly tried many of those solutions and ended up with this working solution:

Add this utility method that will be used several times below to get the number of fragments in your backstack:

protected int getFragmentCount() {
    return getSupportFragmentManager().getBackStackEntryCount();
}

Then, when you add/replace your fragment using FragmentTransaction method, generate a unique tag to your fragment (e.g.: by using the number of fragments in your stack):

getSupportFragmentManager().beginTransaction().add(yourContainerId, yourFragment, Integer.toString(getFragmentCount()));

Finally, you can find any of your fragments in your backstack with this method:

private Fragment getFragmentAt(int index) {
    return getFragmentCount() > 0 ? getSupportFragmentManager().findFragmentByTag(Integer.toString(index)) : null;
}

Therefore, fetching the top fragment in your backstack can be easily achieved by calling:

protected Fragment getCurrentFragment() {
    return getFragmentAt(getFragmentCount() - 1);
}

Hope this helps!

User · Answer

you can use getBackStackEntryAt    In order to know how many entry the activity holds  in the backstack you can use getBackStackEntryCount     int lastFragmentCount   getBackStackEntryCount   - 1

User · Answer

Actually there s no latest fragment added to the stack because you can add several or fragments to the stack in a single transaction or just remove fragments without adding a new one   If you really want to have a stack of fragments and to be able to access a fragment by its index in the stack  you d better have an abstraction layer over the FragmentManager and its backstack  Here s how you can do it   public class FragmentStackManager     private final FragmentManager fragmentManager    private final int containerId     private final List lt Fragment gt  fragments   new ArrayList lt  gt        public FragmentStackManager final FragmentManager fragmentManager        final int containerId        this fragmentManager   fragmentManager      this containerId   containerId         public Parcelable saveState         final Bundle state   new Bundle fragments size         for  int i   0  count   fragments size    i  lt  count    i          fragmentManager putFragment state  Integer toString i   fragments get i              return state         public void restoreState final Parcelable state        if  state instanceof Bundle          final Bundle bundle    Bundle  state        int index   0        while  true            final Fragment fragment               fragmentManager getFragment bundle  Integer toString index            if  fragment    null              break                     fragments add fragment           index    1                       public void replace final Fragment fragment        fragmentManager popBackStackImmediate          null  FragmentManager POP BACK STACK INCLUSIVE       fragmentManager beginTransaction            replace containerId  fragment           addToBackStack null           commit        fragmentManager executePendingTransactions         fragments clear        fragments add fragment          public void push final Fragment fragment        fragmentManager          beginTransaction            replace containerId  fragment           addToBackStack null           commit        fragmentManager executePendingTransactions         fragments add fragment          public boolean pop         if  isEmpty            return false             fragmentManager popBackStackImmediate         fragments remove fragments size   - 1       return true         public boolean isEmpty         return fragments isEmpty           public int size         return fragments size           public Fragment getFragment final int index        return fragments get index           Now instead of adding and removing fragments by calling FragmentManager directly  you should use push    replace    and pop   methods of FragmentStackManager  And you will be able to access the topmost fragment by just calling stack get stack size   - 1    But if you like hacks  I have to other ways of doing similar things  The only thing I have to mention is that these hacks will work only with support fragments   The first hack is just to get all active fragments added to the fragment manager  If you just replace fragments one by one and pop the from the stack this method will return the topmost fragment   public class BackStackHelper     public static List lt Fragment gt  getTopFragments        final FragmentManager fragmentManager        final List lt Fragment gt  fragments   fragmentManager getFragments        final List lt Fragment gt  topFragments   new ArrayList lt  gt          for  final Fragment fragment   fragments          if  fragment    null  amp  amp  fragment isResumed              topFragments add fragment                      return topFragments          The second approach is event more hacky and allows you to get all fragments added in the last transaction for which addToBackStack has been called   package android support v4 app   import java util ArrayList  import java util Collections  import java util List   public class BackStackHelper     public static List lt Fragment gt  getTopFragments        final FragmentManager fragmentManager        if  fragmentManager getBackStackEntryCount      0          return Collections emptyList               final List lt Fragment gt  fragments   new ArrayList lt  gt          final int count   fragmentManager getBackStackEntryCount        final BackStackRecord record            BackStackRecord  fragmentManager getBackStackEntryAt count - 1       BackStackRecord Op op   record mHead      while  op    null          switch  op cmd            case BackStackRecord OP ADD          case BackStackRecord OP REPLACE          case BackStackRecord OP SHOW          case BackStackRecord OP ATTACH            fragments add op fragment                 op   op next             return fragments          Please notice that in this case you have to put this class into android support v4 app package

User · Answer

You can use the getName   method of FragmentManager BackStackEntry which was introduced in API level 14  This method will return a tag which was the one you used when you added the Fragment to the backstack with addTobackStack tag    int index   getActivity   getFragmentManager   getBackStackEntryCount   - 1 FragmentManager BackStackEntry backEntry   getFragmentManager   getBackStackEntryAt index   String tag   backEntry getName    Fragment fragment   getFragmentManager   findFragmentByTag tag     You need to make sure that you added the fragment to the backstack like this   fragmentTransaction addToBackStack tag

User · Answer

I will add something to Deepak Goel s answer since a lot of people  me included  were getting a null by using his method  Apparently to make the tag work when you add a fragment to the backstack you should be doing it like this   getSupportFragmentManager beginTransaction   replace R id container id FragmentName TAG NAME  addToBackStack TAG NAME  commit      You need to add the same tag twice   I would have commented but i don t have 50 reputation

User · Answer

Keep your own back stack  myBackStack  As you Add a fragment to the FragmentManager  also add it to myBackStack  In onBackStackChanged   pop from myBackStack when its length is greater than getBackStackEntryCount

User · Answer

Just took  roghayeh hosseini  correct  answer and made it in Kotlin for those here in 2017     fun getTopFragment    Fragment        supportFragmentManager run           return when  backStackEntryCount                0 - gt  null             else - gt  findFragmentByTag getBackStackEntryAt backStackEntryCount - 1  name                       This should be called from inside an Activity   Enjoy

User · Answer

this helper method get fragment from top of stack   public Fragment getTopFragment         if  getSupportFragmentManager   getBackStackEntryCount      0            return null            String fragmentTag   getSupportFragmentManager   getBackStackEntryAt getSupportFragmentManager   getBackStackEntryCount   - 1  getName        return getSupportFragmentManager   findFragmentByTag fragmentTag

User · Answer

If you use addToBackStack    you can use following code   List lt Fragment gt  fragments   fragmentManager getFragments    activeFragment   fragments get fragments size   - 1

User · Answer

There is a list of fragments in the fragmentMananger  Be aware that removing a fragment  does not make the list size decrease  the fragment entry just turn to null   Therefore  a valid solution would be   public Fragment getTopFragment      List lt Fragment gt  fragentList   fragmentManager getFragments     Fragment top   null    for  int i   fragentList size   -1  i gt  0   i--       top    Fragment  fragentList get i        if  top    null           return top               return top

User · Answer

Looks like something has changed for the better  because code below works perfectly for me  but I didn t find it in already provided answers   Kotlin   supportFragmentManager fragments supportFragmentManager fragments size - 1    Java   getSupportFragmentManager   getFragments    get getSupportFragmentManager   getFragments   size   - 1

User · Answer

FragmentManager findFragmentById fragmentsContainerId     function returns link to top Fragment in backstack  Usage example       fragmentManager addOnBackStackChangedListener new OnBackStackChangedListener              Override         public void onBackStackChanged                 Fragment fr   fragmentManager findFragmentById R id fragmentsContainer               if fr  null                   Log e  fragment    fr getClass   getSimpleName

User · Answer

Kotlin  activity supportFragmentManager fragments last

User · Answer

Kotlin Developers can use this to get the current fragment          supportFragmentManager addOnBackStackChangedListener           val myFragment   supportFragmentManager fragments last            if  null    myFragment  amp  amp  myFragment is HomeFragment                  HomeFragment is visible or currently loaded           else                 your code

User · Answer

The highest  Deepak Goel  answer didn t work well for me  Somehow the tag wasn t added properly   I ended up just sending the ID of the fragment through the flow  using intents  and retrieving it directly from fragment manager

User · Answer

The answer given by deepak goel does not work for me because I always get null from entry getName     What I do is to set a Tag to the fragment this way   ft add R id fragment container  fragmentIn  FRAGMENT TAG     Where ft is my fragment transaction and FRAGMENT TAG is the tag  Then I use this code to get the fragment   Fragment prev fragment   fragmentManager findFragmentByTag FRAGMENT TAG

User · Answer

Or you may just add a tag when adding fragments corresponding to their content and use simple static String field  also you may save it in activity instance bundle in onSaveInstanceState Bundle  method  to hold last added fragment tag and get this fragment byTag   at any time you need

[android] get the latest fragment in backstack

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