Android Fragment handle back button press

Question

I have some fragments in my activity   1    2    3    4    5    6    And on Back Button Press I must to return from  2  to  1  if current active fragment is  2   or do nothing otherwise   What is the best practise to do that   EDIT  Application must not return to  2  from  3     6

User · Answer

rootView setFocusableInTouchMode true               rootView requestFocus                rootView setOnKeyListener new View OnKeyListener                  Override             public boolean onKey View v  int keyCode  KeyEvent event                  if  keyCode    KeyEvent KEYCODE BACK                      Fragment NameofFragment   new NameofFragment                   FragmentTransaction  transaction getFragmentManager   beginTransaction                    transaction replace R id frame container NameofFragment                    transaction commit                     return true                            return false                         return rootView

User · Answer

After looking at all solutions  I realised there is a much simpler solution   In your activity s onBackPressed   that is hosting all your fragments  find the fragment that you want to prevent back press  Then if found  just return  Then popBackStack will never happen for this fragment       Override public void onBackPressed              Fragment1 fragment1    Fragment1  getFragmentManager   findFragmentByTag    Fragment1              if  fragment1    null              return           if  getFragmentManager   getBackStackEntryCount    gt  0               getFragmentManager   popBackStack

User · Answer

If you manage the flow of adding to back stack every transaction  then you can do something like this in order to show the previous fragment when the user presses back button  you could map the home button too     Override public void onBackPressed         if  getFragmentManager   getBackStackEntryCount    gt  0          getFragmentManager   popBackStack        else         super onBackPressed

User · Answer

I think the easiest way is to create an interface  and in the Activity check if the fragment is of the interface type  and if so  call its method to handle the pop  Here s the interface to implement in the fragment    public interface BackPressedFragment           Note for this to work  name AND tag must be set anytime the fragment is added to back stack  e g         getActivity   getSupportFragmentManager   beginTransaction                          replace R id fragment container  MyFragment newInstance     MY FRAG TAG                          addToBackStack  MY FRAG TAG                          commit           This is really an override  Should call popBackStack itself      void onPopBackStack        Here s how to implement it   public class MyFragment extends Fragment implements BackPressedFragment      Override     public void onPopBackStack                Your code goes here  do anything you want             getActivity   getSupportFragmentManager   popBackStack        And in your Activity  when you handle the pop  likely in both onBackPressed and onOptionsItemSelected   pop the backstack using this method   public void popBackStack         FragmentManager fm   getSupportFragmentManager           Call current fragment s onPopBackStack if it has one      String fragmentTag   fm getBackStackEntryAt fm getBackStackEntryCount   - 1  getName        Fragment currentFragment   getSupportFragmentManager   findFragmentByTag fragmentTag       if  currentFragment instanceof BackPressedFragment            BackPressedFragment currentFragment  onPopBackStack        else         fm popBackStack

User · Answer

if you are using FragmentActivity  then do like this  first call This inside your Fragment   public void callParentMethod        getActivity   onBackPressed        and then Call onBackPressed method in side your parent FragmentActivity class    Override public void onBackPressed         super onBackPressed        create a dialog to ask yes no question whether or not the user wants to exit

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Or you could use getSupportFragmentManager   getBackStackEntryCount   to check what to do    Override     public void onBackPressed              logger d         back stack entry count       getSupportFragmentManager   getBackStackEntryCount              if  getSupportFragmentManager   getBackStackEntryCount      0                    only show dialog while there s back stack entry             dialog show getSupportFragmentManager     ConfirmDialogFragment               else if  getSupportFragmentManager   getBackStackEntryCount      0                    or just go back to main activity             super onBackPressed

User · Answer

In your oncreateView   method you need to write this code and in KEYCODE BACk condition you can write whatever the functionality you want  View v   inflater inflate R layout xyz  container  false     Back pressed Logic for fragment  v setFocusableInTouchMode true    v requestFocus     v setOnKeyListener new View OnKeyListener           Override      public boolean onKey View v  int keyCode  KeyEvent event            if  event getAction      KeyEvent ACTION DOWN                if  keyCode    KeyEvent KEYCODE BACK                    getActivity   finish                     Intent intent   new Intent getActivity    MainActivity class                   startActivity intent                    return true                                     return false

User · Answer

The most ideal way of doing this is found here  Fragment  which callback invoked when press back button  amp  customize it  public class MyActivity extends Activity                   Defined in Activity class  so override      Override     public void onBackPressed                 super onBackPressed            myFragment onBackPressed             public class MyFragment extends Fragment         Your created method     public static void onBackPressed                   Pop Fragments off backstack and do your other checks

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I m working with SlidingMenu and Fragment  present my case here and hope helps somebody   Logic when  Back  key pressed     When SlidingMenu shows  close it  no more things to do  Or when 2nd or more  Fragment showing  slide back to previous Fragment  and no more things to do  SlidingMenu not shows  current Fragment is  0  do the original  Back  key does   public class Main extends SherlockFragmentActivity     private SlidingMenu menu null    Constants VP new ViewPager this        Some stuff        Override   public void onBackPressed           if menu isMenuShowing                menu showContent true     Close SlidingMenu when menu showing       return            else             int page Constants VP getCurrentItem          if page gt 0                  Constants VP setCurrentItem page-1  true     Show previous fragment until Fragment 0         return                else        super onBackPressed       If SlidingMenu is not showing and current Fragment is  0  do the original  Back  key does  In my case is exit from APP

User · Answer

Add this code in your Activity   Override  public void onBackPressed         if  getFragmentManager   getBackStackEntryCount      0            super onBackPressed          else           getFragmentManager   popBackStack              And add this line in your Fragment before commit    ft addToBackStack  Any name

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Working Code   package com example keralapolice   import android app Fragment  import android app FragmentManager  import android app FragmentManager OnBackStackChangedListener  import android content Intent  import android os Bundle  import android util Log  import android view Gravity  import android view KeyEvent  import android view LayoutInflater  import android view View  import android view ViewGroup  import android widget Toast   public class ChiefFragment extends Fragment       View view          public OnBackPressedListener onBackPressedListener        Override     public View onCreateView LayoutInflater inflater              ViewGroup container  Bundle args             view   inflater inflate R layout activity chief  container  false           getActivity   getActionBar   hide            view setFocusableInTouchMode true           view requestFocus            view setOnKeyListener new View OnKeyListener                  Override             public boolean onKey View v  int keyCode  KeyEvent event                    Log i getTag     keyCode      keyCode                   if  keyCode    KeyEvent KEYCODE BACK                        getActivity   getActionBar   show                        Log i getTag     onKey Back listener is working                           getFragmentManager   popBackStack null  FragmentManager POP BACK STACK INCLUSIVE                          String cameback  CameBack                       Intent i   new Intent getActivity    home class                          i putExtra  Comingback   cameback                       startActivity i                       return true                    else                       return false                                                      return view

User · Answer

Add addToBackStack   to fragment transaction and then use below code for Implementing Back Navigation for Fragments  getSupportFragmentManager   addOnBackStackChangedListener      new FragmentManager OnBackStackChangedListener             public void onBackStackChanged                    Update your UI here

User · Answer

Create interfaces   BackButtonHandlerInterface  public interface BackButtonHandlerInterface       void addBackClickListener  OnBackClickListener onBackClickListener       void removeBackClickListener  OnBackClickListener onBackClickListener       OnBackClickListener  public interface OnBackClickListener        boolean onBackClick        In Activity   public class MainActivity extends AppCompatActivity implements BackButtonHandlerInterface        private ArrayList lt WeakReference lt OnBackClickListener gt  gt  backClickListenersList   new ArrayList lt  gt           Override     public void addBackClickListener OnBackClickListener onBackClickListener            backClickListenersList add new WeakReference lt  gt  onBackClickListener                Override     public void removeBackClickListener OnBackClickListener onBackClickListener            for  Iterator lt WeakReference lt OnBackClickListener gt  gt  iterator   backClickListenersList iterator             iterator hasNext                  WeakReference lt OnBackClickListener gt  weakRef   iterator next                if  weakRef get      onBackClickListener                   iterator remove                                        Override     public void onBackPressed             if  fragmentsBackKeyIntercept                 super onBackPressed                         private boolean fragmentsBackKeyIntercept             boolean isIntercept   false          for  WeakReference lt OnBackClickListener gt  weakRef   backClickListenersList                OnBackClickListener onBackClickListener   weakRef get                if  onBackClickListener    null                    boolean isFragmIntercept   onBackClickListener onBackClick                    if   isIntercept  isIntercept   isFragmIntercept                                  return isIntercept            In Fragment   public class MyFragment extends Fragment implements OnBackClickListener       private BackButtonHandlerInterface backButtonHandler        Override     public void onAttach Activity activity            super onAttach activity           backButtonHandler    BackButtonHandlerInterface  activity          backButtonHandler addBackClickListener this               Override     public void onDetach             super onDetach            backButtonHandler removeBackClickListener this           backButtonHandler   null              Override     public boolean onBackClick               This method handle onBackPressed    return true or false         return false             Update  Provide custom back navigation  class MyFragment   Fragment          override fun onCreate savedInstanceState  Bundle             super onCreate savedInstanceState              This callback will only be called when MyFragment is at least Started          val callback   requireActivity   onBackPressedDispatcher addCallback this                   Handle the back button event                       The callback can be enabled or disabled here or in the lambda

User · Answer

if you overide the onKey method for the fragment view you re gonna need        view setFocusableInTouchMode true       view requestFocus        view setOnKeyListener new View OnKeyListener                  Override             public boolean onKey View v  int keyCode  KeyEvent event                    Log i tag   keyCode      keyCode                   if  keyCode    KeyEvent KEYCODE BACK  amp  amp  event getAction      KeyEvent ACTION UP                        Log i tag   onKey Back listener is working                           getFragmentManager   popBackStack null  FragmentManager POP BACK STACK INCLUSIVE                       return true                                     return false

User · Answer

We created tiny library for handling back press across multiple fragments and or in Activity  Usage is as simple as adding dependency in your gradle file   compile  net skoumal fragmentback fragment-back 0 1 0    Let your fragment implement BackFragment interface   public abstract class MyFragment extends Fragment implements BackFragment        public boolean onBackPressed                 -- your code --             return true if you want to consume back-pressed event         return false             public int getBackPriority             return NORMAL BACK PRIORITY            Notify your fragments about back presses   public class MainActivity extends AppCompatActivity         Override     public void onBackPressed                first ask your fragments to handle back-pressed event         if  BackFragmentHelper fireOnBackPressedEvent this                    lets do the default back action if fragments don t consume it             super onBackPressed                        For more details and other use-cases visit GitHub page   https   github com skoumalcz fragment-back

User · Answer

This is a very good and reliable solution  http   vinsol com blog 2014 10 01 handling-back-button-press-inside-fragments   The guy has made an abstract fragment that handles the backPress behaviour and is switching between the active fragments using the strategy pattern    For some of you there maybe a little drawback in the abstract class     Shortly  the solution from the link goes like this      Abstract Fragment handling the back presses  public abstract class BackHandledFragment extends Fragment       protected BackHandlerInterface backHandlerInterface      public abstract String getTagText        public abstract boolean onBackPressed          Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           if   getActivity    instanceof BackHandlerInterface                 throw new ClassCastException  Hosting activity must implement BackHandlerInterface              else               backHandlerInterface    BackHandlerInterface  getActivity                          Override     public void onStart             super onStart                Mark this fragment as the selected Fragment          backHandlerInterface setSelectedFragment this              public interface BackHandlerInterface           public void setSelectedFragment BackHandledFragment backHandledFragment                And usage in the activity      BASIC ACTIVITY CODE THAT LETS ITS FRAGMENT UTILIZE onBackPress EVENTS     IN AN ADAPTIVE AND ORGANIZED PATTERN USING BackHandledFragment  public class TheActivity extends FragmentActivity implements BackHandlerInterface       private BackHandledFragment selectedFragment        Override     public void onBackPressed             if selectedFragment    null     selectedFragment onBackPressed                     Selected fragment did not consume the back press event              super onBackPressed                          Override     public void setSelectedFragment BackHandledFragment selectedFragment            this selectedFragment   selectedFragment

User · Answer

You can use from getActionBar   setDisplayHomeAsUpEnabled       Override public void onBackStackChanged         int backStackEntryCount   getFragmentManager   getBackStackEntryCount         if backStackEntryCount  gt  0           getActionBar   setDisplayHomeAsUpEnabled true        else          getActionBar   setDisplayHomeAsUpEnabled false

User · Answer

in fragment class put this code for back event    rootView setFocusableInTouchMode true           rootView requestFocus            rootView setOnKeyListener  new OnKeyListener                          Override             public boolean onKey  View v  int keyCode  KeyEvent event                                 if  keyCode    KeyEvent KEYCODE BACK                                         FragmentManager fragmentManager   getFragmentManager                        fragmentManager beginTransaction                                replace R id frame container  new Book service provider    commit                         return true                                    return false

User · Answer

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  amp  amp  keyCode    KeyEvent KEYCODE BACK                        if  mDrawerLayout isDrawerOpen GravityCompat START                            mDrawerLayout closeDrawer GravityCompat START                                             return true                                     return false

User · Answer

If you want to handle hardware Back key event than you have to do following code in your onActivityCreated   method of Fragment   You also need to check Action Down or Action UP event  If you will not check then onKey   Method will call 2 times   Also  If your rootview getView    will not contain focus then it will not work  If you have clicked on any control then again you need to give focus to rootview using  getView   requestFocus    After this only onKeydown   will call   getView   setFocusableInTouchMode true   getView   requestFocus     getView   setOnKeyListener new OnKeyListener              Override         public boolean onKey View v  int keyCode  KeyEvent event                    if  event getAction      KeyEvent ACTION DOWN                        if  keyCode    KeyEvent KEYCODE BACK                            Toast makeText getActivity     Back Pressed   Toast LENGTH SHORT  show                        return true                                                          return false                              Working very well for me

User · Answer

Checking the backstack works perfectly     Override public boolean onKeyDown int keyCode  KeyEvent event        if  keyCode    KeyEvent KEYCODE BACK                if  getFragmentManager   getBackStackEntryCount      1                           DO something here since there is only one fragment left                Popping a dialog asking to quit the application             return false                      return super onKeyDown keyCode  event

User · Answer

I d rather do something like this   private final static String TAG FRAGMENT    TAG FRAGMENT    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         and then you define a method allowBackPressed with the logic to allow back pressed or not         super onBackPressed

User · Answer

For Those Who Use Static Fragment  In a case if you have a static fragment then It would be preferable   Make an instance object of your fragment  private static MyFragment instance null    in onCreate   of MyFragment initialize that instance    instance this    also make a function to get Instance   public static MyFragment getInstance       return instance      also make functions   public boolean allowBackPressed        if allowBack  true           return true            return false         allowBack is a boolean variable that will be set to true at the action     where you want that your backButton should not close activity  In my case I open     Navigation Drawer then I set it to true  so when I press backbutton my     drawer should be get closed  public void performSomeAction             Your code        Here I have closed my drawer     In Your Activity You can do    Override public void onBackPressed          if  MyFragment getInstance   allowBackPressed               MyFragment getInstance   performSomeAction              else          super onBackPressed

User · Answer

When you are transitioning between Fragments  call addToBackStack   as part of your FragmentTransaction   FragmentTransaction tx   fragmentManager beginTransation    tx replace  R id fragment  new MyFragment     addToBackStack   tag    commit      If you require more detailed control  i e  when some Fragments are visible  you want to suppress the back key  you can set an OnKeyListener on the parent view of your fragment     You need to add the following line for this solution to work  thanks skayred fragment getView   setFocusableInTouchMode true   fragment getView   requestFocus    fragment getView   setOnKeyListener  new OnKeyListener          Override     public boolean onKey  View v  int keyCode  KeyEvent event                 if  keyCode    KeyEvent KEYCODE BACK                         return true                    return false

User · Answer

Use addToBackStack method when replacing one fragment by another   getFragmentManager   beginTransaction   replace R id content frame  fragment  addToBackStack  my fragment   commit      Then in your activity  use the following code to go back from a fragment to another  the previous one     Override public void onBackPressed         if  getFragmentManager   getBackStackEntryCount    gt  0            getFragmentManager   popBackStack          else           super onBackPressed

[android] Android Fragment handle back button press

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