Fragment

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Fragment, Android Jetpack UI Components, A basic unit of composable UI

Android introduced fragments in Android 3.0 (API level 11), A Fragment is a behavior or a portion of user interface in a FragmentActivity. A FragmentActivity shall contain one or more reusable fragments.

Fragment will have its own life cycle, and directly affected by the host activity's lifecycle.

Fragment Life Cycle

• onAttach()
• onCreate()
• onCreateView()
• onActivityCreated()
• onStart()
• onResume()
• onPause()
• onStop()
• onDestroyView()
• onDestroy()
• onDetach()

There are two ways you can add a fragment to the activity layout

• Declare the fragment inside the activity's layout file.
• Programmatically add the fragment to an existing ViewGroup.

Declare the fragment inside the activity's layout file.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <fragment android:name="com.freedomtutorials.MyFragment"
            android:id="@+id/list"
            android:layout_weight="2"
            android:layout_width="2dp"
            android:layout_height="match_parent" />
</LinearLayout>

Fragments will has its own class to implement, and in the <fragment> definition of parent activity layout xml file, the android:name attribute specifies the Fragment class to instantiate.

Programmatically add the fragment to an existing ViewGroup.

 //get the instance of FragmentManager, Method of FragmentActivity subclass
 FragmentManager objFragmentManager = getSupportFragmentManager();

 //begin fragment transaction 
 FragmentTransaction objFragmentTransaction = objFragmentManager.beginTransaction();

 //create instance of your Fragment implementation
 MyFragment objMyfragment = new MyFragment();

 //add it to fragment transaction
 objFragmentTransaction.add(R.id.my_fragment_layout_container, objMyfragment);

 //commit 
 objFragmentTransaction.commit(); 

Finding and Access Fragment instance in Activity

MyFragment objMyfragment = (MyFragment) getSupportFragmentManager().findFragmentById(R.id.my_fragment_layout_container);