Create Fragments

Add fragments to your app.

Create a new class for our Fragment:
public class AppFragment extends Fragment {

    public AppFragment() { // Empty constructor
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { // Essential
        View rootView = inflater.inflate(R.layout.our_fragment, container, false); // Use a custom layout file (see below)

        ImageView imageView = rootView.findViewById(R.id.ourImageView); // Here we find a View within the layout

        imageView.setImageResource(R.drawable.anImage); // And allocate an image to it

        return rootView;
    }
}

Our layout file for the Fragment, our_fragment.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/ourImageView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:contentDescription="An Image"
        tools:srcCompat="@drawable/anImage" /> // Placeholder image
</LinearLayout>

Create an instance of our Fragment in the Activity and use FragmentManager to add it to the layout for the Activity:
        AppFragment aFragment = new AppFragment(); // New instance of our custom Fragment

        FragmentManager fragmentManager = getSupportFragmentManager();

        fragmentManager.beginTransaction()
                .add(R.id.fragment_container, aFragment) // Adds the new fragment to an element of the Activity layout (see below)
                .commit();

Our layout file for the Activity, activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
    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"
    tools:context="com.example.android.app.MainActivity">

    <LinearLayout
        android:id="@+id/main_activity_linear_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <FrameLayout android:id="@+id/fragment_container" // View that will contain the Fragment
        android:layout_width="match_parent"
        android:layout_height="180dp"
        android:scaleType="centerInside"/>

    </LinearLayout>
</ScrollView>