Fragment, Fragment BackStack, POP Fragment

A fragment is an independent Android component which can be used by an activity. A fragment encapsulates functionality so that it is easier to reuse within activities and layouts.

A fragment runs in the context of an activity, but has its own life cycle and typically its own user interface. It is also possible to define fragments without an user interface.

In this tutorial i will cover creation of fragment, BackStack, POP From BackStack etc.

Download Demo

Steps to use Fragment in your project.

1. Crate a project(FragmentDemo) in android studio.
2. Open your main_activity.xml and update it-
   

   <?xml version="1.0" encoding="utf-8"?>
   
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:tools="http://schemas.android.com/tools"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:orientation="vertical"
       tools:context="com.pankaj.fragment.demo.MainActivity">
   
       <LinearLayout
           android:layout_width="match_parent"
           android:layout_height="wrap_content"
           android:orientation="horizontal">
   
           <Button
               android:layout_width="wrap_content"
               android:layout_height="match_parent"
               android:onClick="fragmentOne"
               android:text="fragment One" />
   
           <Button
               android:layout_width="wrap_content"
               android:layout_height="match_parent"
               android:onClick="fragmentTwo"
               android:text="fragment Two" />
   
           <Button
               android:layout_width="wrap_content"
               android:layout_height="match_parent"
               android:onClick="fragmentWhree"
               android:text="fragment Three" />
       </LinearLayout>
   
       <FrameLayout
           android:id="@+id/content_frame"
           android:layout_width="match_parent"
           android:layout_height="match_parent"></FrameLayout>
   
   </LinearLayout>

    
3.  Now Create a class  Utills.JAVA class and update it. "replaceFragment(fragment, fragmentManager)" is used to  check the instance of the fragment, if a instance of fragment is already added in back stack then, It will pop that fragment, else will create new instance of this given fragment.

   package com.pankaj.fragment.demo.utils;
   
   import android.content.Context;
   import android.support.v4.app.ActivityCompat;
   import android.support.v4.app.Fragment;
   import android.support.v4.app.FragmentManager;
   import android.support.v4.app.FragmentTransaction;
   import com.pankaj.fragment.demo.R;
   
   /**
    * Created by android_studio on 23/12/16.
    */
   public class utils {
   
   //________This method will be check, if a instance of fragment is already added in back stack then, It will pop that fragment, else will create new instance.
       public static void replaceFragment(Fragment fragment, FragmentManager manager) {
           String backStateName = fragment.getClass().getName();
           boolean fragmentPopped = manager.popBackStackImmediate(backStateName, 0);
   
    //fragment not in back stack, create it.     
   if (!fragmentPopped) { 
               FragmentTransaction ft = manager.beginTransaction();
               ft.replace(R.id.content_frame, fragment);
               ft.addToBackStack(backStateName);
               ft.commit();
           }
       }
   }
   

4. 
   
   
   
5.  Now create three fragment FragmentOne.Java, FragmentTwo.Java and FragmentThree.Java and update to below code.
   
   FragmentOne.Java

   package com.pankaj.fragment.demo.fragments;
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import android.widget.Button;
   import com.pankaj.fragment.demo.R;
   import com.pankaj.fragment.demo.inner_fragments_for_fragment_one.FragmentInnerA;
   import com.pankaj.fragment.demo.utils.utils;
   /**
    * Created by android_studio on 23/12/16.
    */
   public class FragmentOne extends Fragment {
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
        
       //________create the object of main view for FragmentOne 
           View v = inflater.inflate(R.layout.fragment_one, null);
   
           
           Button innerFragmentA = (Button) v.findViewById(R.id.innerFragmentA);
   
           //________add listener to innerFragmentA button
           innerFragmentA.setOnClickListener(new View.OnClickListener() {
   
               @Override
               public void onClick(View view) {
                   
                   //_________replace the fragment to inner fragment
                   utils.replaceFragment(new FragmentInnerA(), getActivity().getSupportFragmentManager() );
               }
           });
    
    //________return the object of main view for FragmentOne
           return v;
       }
   }
   
   

   
   FragmentTwo.Java

   package com.pankaj.fragment.demo.fragments;
   
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import android.widget.Button;
   import com.pankaj.fragment.demo.R;
   import com.pankaj.fragment.demo.inner_fragment_for_fragment_two.FragmentTwoInnerA;
   import com.pankaj.fragment.demo.utils.utils;
   
   /**
    * Created by android_studio on 23/12/16.
    */
   
   public class FragmentTwo extends Fragment {
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
   
           //________create the object of main view for FragmentTwo
           View v = inflater.inflate(R.layout.fragment_two, null);
   
           //________create the object of button innerFragmentA
           Button FragmentTwoInnerFragmentA = (Button) v.findViewById(R.id.FragmentTwoInnerFragmentA);
   
           //________add listener to FragmentTwoInnerFragmentA button
           FragmentTwoInnerFragmentA.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View view) {
   
                   //_________replace the fragment to inner fragment
                   utils.replaceFragment(new FragmentTwoInnerA(), getActivity().getSupportFragmentManager());
               }
           });
   
           //________return the object of main view for FragmentTwo
           return v;
       }
   }
   

   
   FragmentThree.Java

    
   package com.pankaj.fragment.demo.fragments;
   
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import android.widget.Button;
   import com.pankaj.fragment.demo.R;
   import com.pankaj.fragment.demo.inner_fragment_for_fragment_three.FragmentThreeInnerA;
   import com.pankaj.fragment.demo.inner_fragment_for_fragment_two.FragmentTwoInnerA;
   import com.pankaj.fragment.demo.utils.utils;
   
   /**
    * Created by android_studio on 23/12/16.
    */
   
   public class FragmentThree extends Fragment {
   
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
   
           //________create the object of main view for FragmentTwo
           View v = inflater.inflate(R.layout.fragment_three, null);
   
           //________create the object of button FragmentThreeInnerFragmentA
           Button FragmentThreeInnerFragmentA = (Button) v.findViewById(R.id.FragmentThreeInnerFragmentA);
   
           //________add listener to FragmentThreeInnerFragmentA button
           FragmentThreeInnerFragmentA.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View view) {
   
                   //_________replace the fragment to inner fragment
                   utils.replaceFragment(new FragmentThreeInnerA(), getActivity().getSupportFragmentManager());
               }
           });
   
           //________return the object of main view for FragmentThree
           return v;
       }
   } 

6.   Create XML for all three fragment.
   fragment_one.xml

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment One" />
   
       <Button
           android:layout_width="wrap_content"
           android:text="Fragment One Inner Fragment A"
           android:id="@+id/FragmentOneInnerFragmentA"
           android:layout_height="wrap_content" />
   
   </LinearLayout>
   
   

   
   fragment_two.xml

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment two" />
   
       <Button
           android:id="@+id/FragmentTwoInnerFragmentA"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment Two Inner Fragment A" />
   
   </LinearLayout>
   

   
   fragment_three.xml

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment three" />
   
       <Button
           android:id="@+id/FragmentThreeInnerFragmentA"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment Three Inner Fragment A" />
   
   </LinearLayout>
   

   
   
   
7.  Now create Fragments to open inside the fragments
    FragmentOneInnerA.Java

   package com.pankaj.fragment.demo.inner_fragments_for_fragment_one;
   
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import android.widget.Button;
   import com.pankaj.fragment.demo.R;
   import com.pankaj.fragment.demo.inner_fragment_for_fragment_three.FragmentThreeInnerB;
   import com.pankaj.fragment.demo.utils.utils;
   
   /**
    * Created by android_studio on 23/12/16.
    */
   
   public class FragmenOnetInnerA extends Fragment {
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
   
           //________create the object of main view for FragmenOnetInnerA
           View v = inflater.inflate(R.layout.fragment_inner_a, null);
   
           //________create the object of button FragmentOneInnerFragmentB
           Button FragmentOneInnerFragmentB = (Button) v.findViewById(R.id.FragmentOneInnerFragmentB);
   
           //________add listener to FragmentOneInnerFragmentB button
           FragmentOneInnerFragmentB.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View view) {
   
                   //_________replace the fragment to inner fragment
                   utils.replaceFragment(new FragmentOneInnerB(), getActivity().getSupportFragmentManager());
               }
           });
   
           //________return the object of main view for FragmenOnetInnerA
           return v;
       }
   }
   

   
   
   
   fragment_one_inner_a.xml

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment One Inner Fragment A" />
   
       <Button
           android:id="@+id/FragmentOneInnerFragmentB"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment One Inner Fragment B" />
   </LinearLayout>
   
   

   
   
   
   FragmentOneInnerB.Java

   package com.pankaj.fragment.demo.inner_fragments_for_fragment_one;
   
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import com.pankaj.fragment.demo.R;
   
   /**
    * Created by android_studio on 23/12/16.
    */
   
   public class FragmentOneInnerB extends Fragment {
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
   
           //________create the object of main view for FragmentOneInnerB
           View v = inflater.inflate(R.layout.fragment_one_inner_b, null);
   
           //________return the object of main view for FragmentOneInnerB
           return v;
   
       }
   }

   
   
   
   fragment_one_inner_b.xml

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment One Inner Fragment B" />
   
   </LinearLayout>
   
   

   
   
   
   
   FragmentTwoInnerA.Java

   package com.pankaj.fragment.demo.inner_fragment_for_fragment_two;
   
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import android.widget.Button;
   import com.pankaj.fragment.demo.R;
   import com.pankaj.fragment.demo.utils.utils;
   
   /**
    * Created by android_studio on 23/12/16.
    */
   
   public class FragmentTwoInnerA extends Fragment {
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
   
           //________create the object of main view for FragmentTwoInnerA
           View v = inflater.inflate(R.layout.fragment_two_inner_a, null);
   
           //________return the object of main view for FragmentTwoInnerA
           return v;
       }
   }

   
   
   
   FragmentThree.Java

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment Two Inner Fragment A" />
   
   </LinearLayout>
   
   

   
   
   FragmentThreeInnerA.Java

   package com.pankaj.fragment.demo.inner_fragment_for_fragment_three;
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import android.widget.Button;
   import com.pankaj.fragment.demo.R;
   import com.pankaj.fragment.demo.utils.utils;
   /**
    * Created by android_studio on 23/12/16.
    */
   public class FragmentThreeInnerA extends Fragment {
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
   
           //________create the object of main view for FragmentThreeInnerA
           View v = inflater.inflate(R.layout.fragment_three_inner_a, null);
   
           //________create the object of button FragmentThreeInnerFragmentB
           Button FragmentThreeInnerFragmentB = (Button) v.findViewById(R.id.FragmentThreeInnerFragmentB);
   
           //________add listener to FragmentThreeInnerFragmentB button
           FragmentThreeInnerFragmentB.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View view) {
   
                   //_________replace the fragment to inner fragment
                   utils.replaceFragment(new FragmentThreeInnerB(), getActivity().getSupportFragmentManager());
               }
           });
   
           //________return the object of main view for FragmentThreeInnerA
           return v;
       }
   }
   

   
   fragment_three_inner_a.xml

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment three Inner Fragment A" />
   
       <Button
           android:id="@+id/FragmentThreeInnerFragmentB"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment Three Inner Fragment B" />
   </LinearLayout>
   
   

   
   FragmentThreeInnerB.Java

   package com.pankaj.fragment.demo.inner_fragment_for_fragment_three;
   import android.os.Bundle;
   import android.support.annotation.Nullable;
   import android.support.v4.app.Fragment;
   import android.view.LayoutInflater;
   import android.view.View;
   import android.view.ViewGroup;
   import com.pankaj.fragment.demo.R;
   
   /**
    * Created by android_studio on 23/12/16.
    */
   
   public class FragmentThreeInnerB extends Fragment {
       @Nullable
       @Override
       public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
           super.onCreateView(inflater, container, savedInstanceState);
   
           //________create the object of main view for FragmentThreeInnerB
           View v = inflater.inflate(R.layout.fragment_three_inner_b, null);
   
           //________return the object of main view for FragmentThreeInnerB
           return v;
       }
   }
   

   
   
   
   fragment_three_inner_b.xml

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:gravity="center"
       android:orientation="vertical">
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="Fragment Three Inner Fragment B" />
   
   </LinearLayout>
   
   

   
   
   
   
8.  Now Open your MainActivity.Java and update it. 

   package com.pankaj.fragment.demo;
   
   import android.os.Bundle;
   import android.support.v4.app.FragmentManager;
   import android.support.v7.app.AppCompatActivity;
   import android.view.View;
   import com.pankaj.fragment.demo.fragments.FragmentOne;
   import com.pankaj.fragment.demo.fragments.FragmentThree;
   import com.pankaj.fragment.demo.fragments.FragmentTwo;
   import com.pankaj.fragment.demo.utils.utils;
   
   public class MainActivity extends AppCompatActivity {
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
       }
   
       @Override
       public void onBackPressed() {
   
     //_________check if stack has only one item then close the application else reopen the previous fragment 
           if (getSupportFragmentManager().getBackStackEntryCount() == 1) {
               finish();
           } else {
               super.onBackPressed();
           }
   
       }
   
       //_________methode will be call when user click on Fragment One Button
       public void fragmentOne(View view) {
           FragmentManager manager = getSupportFragmentManager();
           utils.replaceFragment(new FragmentOne(), manager);
       }
   
       //_________methode will be call when user click on Fragment Two Button
       public void fragmentTwo(View view) {
           FragmentManager manager = getSupportFragmentManager();
           utils.replaceFragment(new FragmentTwo(), manager);}
   
       //_________methode will be call when user click on Fragment Three Button
       public void fragmentWhree(View view) {
           FragmentManager manager = getSupportFragmentManager();
           utils.replaceFragment(new FragmentThree(), manager);
       }
   }

   
   
   
9. All the application development process with fragments has completed, Now run the app and click on buttons(fragment One,fragment Two,fragment Three, Fragment three Inner Fragment A, Fragment three Inner Fragment B, Fragment two Inner Fragment A, Fragment one Inner Fragment A, Fragment one Inner Fragment B).
   
   
   
   
   
   
10. Good bye, Thanks to read this blog.

Download Demo