How do I add a Fragment to an Activity with a programmatically created content view

Question

I want to add a Fragment to an Activity that implements its layout programmatically  I looked over the Fragment documentation but there aren t many examples describing what I need  Here is the type of code I tried to write   public class DebugExampleTwo extends Activity        private ExampleTwoFragment mFragment        Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           FrameLayout frame   new FrameLayout this           if  savedInstanceState    null                mFragment   new ExampleTwoFragment                FragmentTransaction ft   getFragmentManager   beginTransaction                ft add frame getId    mFragment  commit                       setContentView frame                  public class ExampleTwoFragment extends Fragment         Override     public View onCreateView LayoutInflater inflater                                ViewGroup container                                Bundle savedInstanceState            Button button   new Button getActivity             button setText  Hello There            return button            This code compiles but crashes at start  probably because my FragmentTransaction add   is incorrect  What is the correct way to do this

User · Answer

This may help you Defining a Fragment create xml file for fragment view fragment abc xml  lt  xml version  quot 1 0 quot  encoding  quot utf-8 quot   gt   lt LinearLayout xmlns android  quot http   schemas android com apk res android quot  android layout width  quot match parent quot  android layout height  quot match parent quot  android orientation  quot vertical quot   gt    lt TextView     android id  quot   id textView1 quot      android layout width  quot wrap content quot      android layout height  quot wrap content quot      android text  quot TextView quot    gt    lt Button     android id  quot   id button1 quot      android layout width  quot wrap content quot      android layout height  quot wrap content quot      android text  quot Button quot    gt    lt  LinearLayout gt   create fragment ABCFragment java import androidx fragment app Fragment   public class FooFragment extends Fragment      The onCreateView method is called when Fragment should create its View object hierarchy     either dynamically or via XML layout inflation     Override public View onCreateView LayoutInflater inflater  ViewGroup parent  Bundle  savedInstanceState           Defines the xml file for the fragment     return inflater inflate R layout fragment abc  parent  false         This event is triggered soon after onCreateView       Any view setup should occur here   E g   view lookups and attaching view listeners   Override public void onViewCreated View view  Bundle savedInstanceState           Setup any handles to view objects here        EditText etFoo    EditText  view findViewById R id etFoo        Add frameLayout in your activity  lt FrameLayout    android id  quot   id your placeholder quot     android layout width  quot match parent quot     android layout height  quot match parent quot  gt   now in activity  add following method protected void setFragment            Begin the transaction     FragmentTransaction ft   getSupportFragmentManager   beginTransaction           Replace the contents of the container with the new fragment     ft replace R id fragment container  new ABCFragment            or ft add R id your placeholder  new ABCFragment            Complete the changes added above     ft commit       reference   https   guides codepath com android creating-and-using-fragments defining-a-fragment

User · Answer

After read all Answers I came up with elegant way   public class MyActivity extends ActionBarActivity     Fragment fragment     Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState        FragmentManager fm   getSupportFragmentManager        fragment   fm findFragmentByTag  myFragmentTag        if  fragment    null            FragmentTransaction ft   fm beginTransaction            fragment  new MyFragment            ft add android R id content fragment  myFragmentTag            ft commit               basically you don t need to add a frameLayout as container of your fragment instead you can add straight the fragment into the android  root View container  IMPORTANT  don t use replace fragment as most of the approach shown here  unless you don t mind to lose fragment variable instance state during onrecreation process

User · Answer

It turns out there s more than one problem with that code  A fragment cannot be declared that way  inside the same java file as the activity but not as a public inner class  The framework expects the fragment s constructor  with no parameters  to be public and visible  Moving the fragment into the Activity as an inner class  or creating a new java file for the fragment fixes that   The second issue is that when you re adding a fragment this way  you must pass a reference to the fragment s containing view  and that view must have a custom id  Using the default id will crash the app  Here s the updated code   public class DebugExampleTwo extends Activity        private static final int CONTENT VIEW ID   10101010        Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           FrameLayout frame   new FrameLayout this           frame setId CONTENT VIEW ID           setContentView frame  new LayoutParams              LayoutParams MATCH PARENT  LayoutParams MATCH PARENT             if  savedInstanceState    null                Fragment newFragment   new DebugExampleTwoFragment                FragmentTransaction ft   getFragmentManager   beginTransaction                ft add CONTENT VIEW ID  newFragment  commit                         public static class DebugExampleTwoFragment extends Fragment            Override         public View onCreateView LayoutInflater inflater  ViewGroup container                  Bundle savedInstanceState                EditText v   new EditText getActivity                 v setText  Hello Fragment                 return v

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public class Example1 extends FragmentActivity             Override         protected void onCreate Bundle savedInstanceState                super onCreate savedInstanceState             DemoFragment fragmentDemo    DemoFragment             getSupportFragmentManager   findFragmentById R id frame container               above part is to determine which fragment is in your frame container           setFragment fragmentDemo                           OR            setFragment new TestFragment1                           This could be moved into an abstract BaseActivity             class for being re-used by several instances         protected void setFragment Fragment fragment                FragmentManager fragmentManager   getSupportFragmentManager                FragmentTransaction fragmentTransaction                    fragmentManager beginTransaction                fragmentTransaction replace android R id content  fragment               fragmentTransaction commit                         To add a fragment into a Activity or FramentActivity it requires a   Container  That container should be a  Framelayout   which can be   included in xml or else you can use the default container for that   like  android R id content  to remove or replace a fragment in   Activity    main xml   lt RelativeLayout     android layout width  match parent      android layout height  match parent   gt    lt  -- Framelayout to display Fragments -- gt      lt FrameLayout         android id    id frame container          android layout width  match parent          android layout height  match parent    gt        lt ImageView         android id    id imagenext          android layout width  wrap content          android layout height  wrap content          android layout alignParentBottom  true          android layout alignParentRight  true          android layout margin  16dp          android src   drawable next    gt   lt  RelativeLayout gt

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Here is what I came up with after reading Tony Wong s comment   public class DebugExampleTwo extends BaseActivity         Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           addFragment android R id content                      new DebugExampleTwoFragment                        DebugExampleTwoFragment FRAGMENT TAG                   public abstract class BaseActivity extends Activity        protected void addFragment  IdRes int containerViewId                                  NonNull Fragment fragment                                  NonNull String fragmentTag            getSupportFragmentManager                    beginTransaction                    add containerViewId  fragment  fragmentTag                   disallowAddToBackStack                    commit               protected void replaceFragment  IdRes int containerViewId                                      NonNull Fragment fragment                                      NonNull String fragmentTag                                      Nullable String backStackStateName            getSupportFragmentManager                    beginTransaction                    replace containerViewId  fragment  fragmentTag                   addToBackStack backStackStateName                   commit                    public class DebugExampleTwoFragment extends Fragment        public static final String FRAGMENT TAG            BuildConfig APPLICATION ID     DEBUG EXAMPLE TWO FRAGMENT TAG                    Kotlin  If you are using Kotlin make sure to take a look at what the Kotlin extensions by Google provide or just write your own

User · Answer

For API level 17 or higher  View generateViewId   will solve this problem  The utility method provides a unique id that is not used in build time

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For attaching fragment to an activity programmatically in Kotlin  you can look at the following code   MainActivity kt  class MainActivity   AppCompatActivity          override fun onCreate savedInstanceState  Bundle             super onCreate savedInstanceState          setContentView R layout activity main                  create fragment instance             val fragment   FragmentName   FragmentName newInstance                   for passing data to fragment             val bundle   Bundle               bundle putString  data to be passed   DATA              fragment arguments   bundle                 check is important to prevent activity from attaching the fragment if already its attached             if  savedInstanceState    null                    supportFragmentManager                      beginTransaction                        add R id fragment container  fragment   fragment name                        commit                                      activity main xml   lt  xml version  1 0  encoding  utf-8   gt   lt androidx constraintlayout widget ConstraintLayout xmlns android  http   schemas android com apk res android      xmlns app  http   schemas android com apk res-auto      xmlns tools  http   schemas android com tools      android layout width  match parent      android layout height  match parent      tools context   ui MainActivity  gt        lt FrameLayout         android id    id fragment container          android layout width  0dp          android layout height  0dp          app layout constraintBottom toBottomOf  parent          app layout constraintEnd toEndOf  parent          app layout constraintStart toStartOf  parent          app layout constraintTop toTopOf  parent    gt   lt  androidx constraintlayout widget ConstraintLayout gt    FragmentName kt  class FragmentName   Fragment          companion object           fun newInstance     FragmentName              override fun onCreateView inflater  LayoutInflater  container  ViewGroup   savedInstanceState  Bundle    View                receiving the data passed from activity here         val data   arguments   getString  data to be passed           return view            override fun onActivityCreated savedInstanceState  Bundle             super onActivityCreated savedInstanceState             If you are familiar with Extensions in Kotlin then you can even better this code by following this article

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public abstract class SingleFragmentActivity extends Activity        public static final String FRAGMENT TAG    single       private Fragment fragment        Override     protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState           if  savedInstanceState    null                fragment   onCreateFragment               getFragmentManager   beginTransaction                       add android R id content  fragment  FRAGMENT TAG                      commit             else              fragment   getFragmentManager   findFragmentByTag FRAGMENT TAG                     public abstract Fragment onCreateFragment        public Fragment getFragment            return fragment            use  public class ViewCatalogItemActivity extends SingleFragmentActivity        Override     public Fragment onCreateFragment             return new FragmentWorkShops

[android] How do I add a Fragment to an Activity with a programmatically created content view

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