How to handle button clicks using the XML onClick within Fragments

Question

Pre-Honeycomb  Android nbsp 3   each Activity was registered to handle button clicks via the onClick tag in a Layout s XML   android onClick  myClickMethod    Within that method you can use view getId   and a switch statement to do the button logic   With the introduction of Honeycomb I m breaking these Activities into Fragments which can be reused inside many different Activities  Most of the behavior of the buttons is Activity independent  and I would like the code to reside inside the Fragments file without using the old  pre 1 6  method of registering the OnClickListener for each button   final Button button    Button  findViewById R id button id   button setOnClickListener new View OnClickListener         public void onClick View v               Perform action on click             The problem is that when my layout s are inflated it is still the hosting Activity that is receiving the button clicks  not the individual Fragments  Is there a good approach to either   Register the fragment to receive the button clicks  Pass the click events from the Activity to the fragment they belong to

User · Answer

This has been working for me  Android studio     Override     public View onCreateView LayoutInflater inflater  ViewGroup container  Bundle savedInstanceState             View rootView   inflater inflate R layout update credential  container  false           Button bt login    Button  rootView findViewById R id btnSend            bt login setOnClickListener new View OnClickListener                  Override             public void onClick View view                     System out println  Hi its me                      end onClick                      return rootView           end onCreateView

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Adding to Blundell s answer  If you have more fragments  with plenty of onClicks   Activity   Fragment someFragment1    Fragment getFragmentManager   findFragmentByTag  someFragment1      Fragment someFragment2    Fragment getFragmentManager   findFragmentByTag  someFragment2      Fragment someFragment3    Fragment getFragmentManager   findFragmentByTag  someFragment3          onCreate etc instantiating your fragments  public void myClickMethod View v     if  someFragment1 isVisible             someFragment1 myClickMethod v      else if someFragment2 isVisible            someFragment2 myClickMethod v      else if someFragment3 isVisible            someFragment3 myClickMethod v              In Your Fragment     public void myClickMethod View v        switch v getid               Just like you were doing

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As I see answers they re somehow old  Recently Google introduce DataBinding which is much easier to handle onClick or assigning in your xml   Here is good example which you can see how to handle this      lt  xml version  1 0  encoding  utf-8   gt   lt layout xmlns android  http   schemas android com apk res android  gt      lt data gt          lt variable name  handlers  type  com example Handlers   gt          lt variable name  user  type  com example User   gt      lt  data gt      lt LinearLayout        android orientation  vertical         android layout width  match parent         android layout height  match parent  gt          lt TextView android layout width  wrap content             android layout height  wrap content             android text    user firstName              android onClick    user isFriend   handlers onClickFriend   handlers onClickEnemy    gt          lt TextView android layout width  wrap content             android layout height  wrap content             android text    user lastName              android onClick    user isFriend   handlers onClickFriend   handlers onClickEnemy    gt      lt  LinearLayout gt   lt  layout gt    There is also very nice tutorial about DataBinding you can find it Here

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You might want to consider using EventBus for decoupled events    You can listen for events very easily  You can also make sure the event is being received on the ui thread  instead of calling runOnUiThread   for yourself for every event subscription   https   github com greenrobot EventBus  from Github      Android optimized event bus that simplifies communication between   Activities  Fragments  Threads  Services  etc  Less code  better   quality

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I prefer using the following solution for handling onClick events  This works for Activity and Fragments as well   public class StartFragment extends Fragment implements OnClickListener        Override     public View onCreateView LayoutInflater inflater  ViewGroup container              Bundle savedInstanceState             View v   inflater inflate R layout fragment start  container  false            Button b    Button  v findViewById R id StartButton           b setOnClickListener this           return v              Override     public void onClick View v            switch  v getId              case R id StartButton                                break

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If you register in xml using android Onclick     callback will be given to the respected Activity under whose context your fragment belongs to  getActivity      If such method not found in the Activity  then system will throw an exception

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You could just do this   Activity   Fragment someFragment            onCreate etc instantiating your fragments  public void myClickMethod View v        someFragment myClickMethod v       Fragment   public void myClickMethod View v        switch v getId                 Just like you were doing                 In response to  Ameen who wanted less coupling so Fragments are reuseable  Interface   public interface XmlClickable       void myClickMethod View v       Activity   XmlClickable someFragment            onCreate  etc  instantiating your fragments casting to your interface    public void myClickMethod View v        someFragment myClickMethod v       Fragment   public class SomeFragment implements XmlClickable         onCreateView  etc    Override public void myClickMethod View v        switch v getId                Just like you were doing

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In my use case  I have 50 odd ImageViews I needed to hook into a single onClick method   My solution is to loop over the views inside the fragment and set the same onclick listener on each       final View OnClickListener imageOnClickListener   new View OnClickListener              Override         public void onClick View v                chosenImage     ImageButton v  getDrawable                          ViewGroup root    ViewGroup  getView   findViewById R id imagesParentView       int childViewCount   root getChildCount        for  int i 0  i  lt  childViewCount  i             View image   root getChildAt i           if  image instanceof ImageButton                  ImageButton image  setOnClickListener imageOnClickListener

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Your Activity is receiving the callback as must have used   mViewPagerCloth setOnClickListener  YourActivityName getActivity       If you want your fragment to receive callback then do this   mViewPagerCloth setOnClickListener this     and implement onClickListener interface on Fragment

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The problem I think is that the view is still the activity  not the fragment  The fragments doesn t have any independent view of its own and is attached to the parent activities view  Thats why the event ends up in the Activity  not the fragment  Its unfortunate  but I think you will need some code to make this work   What I ve been doing during conversions is simply adding a click listener that calls the old event handler   for instance   final Button loginButton    Button  view findViewById R id loginButton   loginButton setOnClickListener new OnClickListener          Override     public void onClick final View v            onLoginClicked v

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ButterKnife is probably the best solution for the clutter problem  It uses annotation processors to generate the so called  old method  boilerplate code   But the onClick method can still be used  with a custom inflator   How to use   Override public View onCreateView LayoutInflater inflater  ViewGroup cnt  Bundle state        inflater   FragmentInflatorFactory inflatorFor inflater  this       return inflater inflate R layout fragment main  cnt  false       Implementation  public class FragmentInflatorFactory implements LayoutInflater Factory        private static final int   sWantedAttrs     android R attr onClick         private static final Method sOnCreateViewMethod      static              We could duplicate its functionallity   or just ignore its a protected method          try               Method method   LayoutInflater class getDeclaredMethod                       onCreateView   String class  AttributeSet class               method setAccessible true               sOnCreateViewMethod   method            catch  NoSuchMethodException e                   Public API  Should not happen              throw new RuntimeException e                        private final LayoutInflater mInflator      private final Object mFragment       public FragmentInflatorFactory LayoutInflater delegate  Object fragment            if  delegate    null    fragment    null                throw new NullPointerException                      mInflator   delegate          mFragment   fragment             public static LayoutInflater inflatorFor LayoutInflater original  Object fragment            LayoutInflater inflator   original cloneInContext original getContext             FragmentInflatorFactory factory   new FragmentInflatorFactory inflator  fragment           inflator setFactory factory           return inflator              Override     public View onCreateView String name  Context context  AttributeSet attrs            if   fragment  equals name                    Let the Activity   private factory   handle it             return null                     View view   null           if  name indexOf         -1                try                   view    View  sOnCreateViewMethod invoke mInflator  name  attrs                 catch  IllegalAccessException e                    throw new AssertionError e                 catch  InvocationTargetException e                    if  e getCause   instanceof ClassNotFoundException                        return null                                    throw new RuntimeException e                           else               try                   view   mInflator createView name  null  attrs                 catch  ClassNotFoundException e                    return null                                   TypedArray a   context obtainStyledAttributes attrs  sWantedAttrs           String methodName   a getString 0           a recycle             if  methodName    null                view setOnClickListener new FragmentClickListener mFragment  methodName                      return view             private static class FragmentClickListener implements OnClickListener            private final Object mFragment          private final String mMethodName          private Method mMethod           public FragmentClickListener Object fragment  String methodName                mFragment   fragment              mMethodName   methodName                      Override         public void onClick View v                if  mMethod    null                    Class lt   gt  clazz   mFragment getClass                    try                       mMethod   clazz getMethod mMethodName  View class                     catch  NoSuchMethodException e                        throw new IllegalStateException                               Cannot find public method     mMethodName     View  on                                         clazz     for onClick                                                 try                   mMethod invoke mFragment  v                 catch  InvocationTargetException e                    throw new RuntimeException e                 catch  IllegalAccessException e                    throw new AssertionError e

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Though I ve spotted some nice answers relying on data binding  I didn t see any going to the full extent with that approach -- in the sense of enabling fragment resolution while allowing for fragment-free layout definitions in XML s   So assuming data binding is enabled  here s a generic solution I can propose  A bit long but it definitely works  with some caveats    Step 1  Custom OnClick Implementation  This will run a fragment-aware search through contexts associated with the tapped-on view  e g  button        CustomOnClick kt   file JvmName  CustomOnClick    package com example  import android app Activity import android content Context import android content ContextWrapper import android view View import androidx fragment app Fragment import androidx fragment app FragmentActivity import java lang reflect Method  fun onClick view  View  methodName  String        resolveOnClickInvocation view  methodName   invoke view     private data class OnClickInvocation val obj  Any  val method  Method        fun invoke view  View            method invoke obj  view           private fun resolveOnClickInvocation view  View  methodName  String   OnClickInvocation        searchContexts view    context - gt          var invocation  OnClickInvocation    null         if  context is Activity                val activity   context as  FragmentActivity                        throw IllegalStateException  A non-FragmentActivity is not supported  looking up an onClick handler of  view                 invocation   getTopFragment activity   let   fragment - gt                  resolveInvocation fragment  methodName                  resolveInvocation context  methodName                    invocation        private fun getTopFragment activity  FragmentActivity   Fragment        val fragments   activity supportFragmentManager fragments     return if  fragments isEmpty    null else fragments last      private fun resolveInvocation target  Any  methodName  String   OnClickInvocation        try           val method   target javaClass getMethod methodName  View  class java          OnClickInvocation target  method        catch  e  NoSuchMethodException            null        private fun  lt T  Any gt  searchContexts view  View  matcher   context  Context  - gt  T    T        var context   view context     while  context    null  amp  amp  context is ContextWrapper            val result   matcher context          if  result    null                context   context baseContext           else               return result                     return null         Note  loosely based on the original Android implementation  see https   android googlesource com platform frameworks base   a175a5b core java android view View java 3025    Step 2  Declarative application in layout files  Then  in data-binding aware XML s    lt layout gt     lt data gt        lt import type  com example CustomOnClick   gt     lt  data gt      lt Button     android onClick     v  - gt  CustomOnClick onClick v   myClickMethod        lt  Button gt   lt  layout gt    Caveats   Assumes a  modern  FragmentActivity based implementation Can only lookup method of  top-most   i e  last  fragment in stack  though that can be fixed  if need be

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I ve recently solved this issue without having to add a method to the context Activity or having to implement OnClickListener  I m not sure if it is a  valid  solution neither  but it works   Based on  https   developer android com tools data-binding guide html binding events  It can be done with data bindings  Just add your fragment instance as a variable  then you can link any method with onClick    lt layout xmlns android  http   schemas android com apk res android      xmlns tools  http   schemas android com tools      tools context  com example testapp fragments CustomFragment  gt        lt data gt           lt variable android name  fragment  android type  com example testapp fragments CustomFragment   gt       lt  data gt       lt LinearLayout         android orientation  vertical          android layout width  match parent          android layout height  match parent  gt            lt ImageButton             android layout width  wrap content              android layout height  wrap content              android src   drawable ic place black 24dp              android onClick       - gt  fragment buttonClicked      gt       lt  LinearLayout gt   lt  layout gt    And the fragment linking code would be     public class CustomFragment extends Fragment                  Override     public View onCreateView LayoutInflater inflater  ViewGroup container                               Bundle savedInstanceState               Inflate the layout for this fragment         View view   inflater inflate R layout fragment person profile  container  false           FragmentCustomBinding binding   DataBindingUtil bind view           binding setFragment this           return view

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This is another way   1 Create a BaseFragment like this   public abstract class BaseFragment extends Fragment implements OnClickListener   2 Use   public class FragmentA extends BaseFragment    instead of   public class FragmentA extends Fragment   3 In your activity   public class MainActivity extends ActionBarActivity implements OnClickListener   and   BaseFragment fragment   new FragmentA   public void onClick View v       fragment onClick v       Hope it helps

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Best solution IMHO   in fragment   protected void addClick int id        try           getView   findViewById id  setOnClickListener this         catch  Exception e            e printStackTrace             public void onClick View v        if  v getId    R id myButton            onMyButtonClick v             then in Fragment s onViewStateRestored    addClick R id myButton

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I would rather go for the click handling in code than using the onClick attribute in XML when working with fragments   This becomes even easier when migrating your activities to fragments  You can just call the click handler  previously set to android onClick in XML  directly from each case block   findViewById R id button login  setOnClickListener clickListener        OnClickListener clickListener   new OnClickListener          Override     public void onClick final View v            switch v getId                 case R id button login                   Which is supposed to be called automatically in your                  activity  which has now changed to a fragment                onLoginClick v                 break              case R id button logout                                        When it comes to handling clicks in fragments  this looks simpler to me than android onClick

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I d like to add to Adjorn Linkz s answer   If you need multiple handlers  you could just use lambda references  void onViewCreated View view  Bundle savedInstanceState        view setOnClickListener this  handler     void handler View v                The trick here is that handler method s signature matches View OnClickListener onClick signature  This way  you won t need the View OnClickListener interface   Also  you won t need any switch statements   Sadly  this method is only limited to interfaces that require a single method  or a lambda

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You can define a callback as an attribute of your XML layout  The article Custom XML Attributes For Your Custom Android Widgets will show you how to do it for a custom widget  Credit goes to Kevin Dion      I m investigating whether I can add styleable attributes to the base Fragment class   The basic idea is to have the same functionality that View implements when dealing with the onClick callback

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The following solution might be a better one to follow  the layout is in fragment my xml  lt  xml version  quot 1 0 quot  encoding  quot utf-8 quot   gt   lt layout xmlns android  quot http   schemas android com apk res android quot      xmlns app  quot http   schemas android com apk res-auto quot  gt        lt data gt           lt variable             name  quot listener quot              type  quot my package MyListener quot    gt       lt  data gt        lt androidx constraintlayout widget ConstraintLayout         android layout width  quot match parent quot          android layout height  quot match parent quot  gt                    lt Button             android id  quot   id moreTextView quot              android layout width  quot wrap content quot              android layout height  quot wrap content quot              android onClick  quot      - gt  listener onClick    quot              android text  quot  string login quot              app layout constraintTop toTopOf  quot parent quot              app layout constraintLeft toLeftOf  quot parent quot              app layout constraintRight toRightOf  quot parent quot    gt       lt  androidx constraintlayout widget ConstraintLayout gt   lt  layout gt   And the Fragment would be as follows class MyFragment   Fragment    MyListener       override fun onCreateView          inflater  LayoutInflater          container  ViewGroup           savedInstanceState  Bundle         View                return FragmentMyBinding inflate                  inflater                  container                  false               apply                   lifecycleOwner   viewLifecycleOwner                 listener   this MyFragment               root            override fun onClick             TODO  quot Not yet implemented quot             interface MyListener      fun onClick

[android] How to handle button clicks using the XML onClick within Fragments

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