Using Fragments in Android

You can use the fragments to display the multiple user-interface panes in single screen. The fragments can be create by creating a subclass of the Fragment class.

You can use the standard class also to create your own fragments. The standard fragment classes are as follows

• DialogFragment - displays the floating dialog window
• ListFragment - display the list of items managed by the adapter
• PreferencesFragment - displays a hierarchy of objects (settings)

The fragment class provide the similar methods like activity to implement its lifecycle. The methods which you must implement while designing the fragment are as follows

OnCreate() - The system calls this when the system is creating the fragment.

OnCreateView() - The system calls this when first time the fragment is drawing its user interface.

OnPause() - The system calls this when user is leaving the fragment and the fragment is moving to back-stack.

For Example the SampleFragment extending the Fragment class. The onCreateView method provides the UI for the fragment. 

public static class SampleFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.sample_fragment, container, false);
    }
}

The sample_fragment.xml is the layout file for the sample fragment.

Now you can use this fragment in your activity using the fragment transactions. To create or start a fragment transaction you need to get the FragmentManager of your activity while activity is running

FragmentManager fragmentManager = getFragmentManager()
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

Now you can add the fragment to the container of the ViewGroup.

SampleFragment fragment = new SampleFragment();
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.commit();

Basics about fragments - Android

Android introduces the fragments in version 3.0 (API Level 11) to provide intuitive user interface design for large screen size of tablets.

A fragment is a sub-module of the activity to represent a portion of the user interface of the activity. You can combine multiple fragments in a single activity to build multi-pane user interface. The fragments are generalized components can be use in multiple activities

Fragments has its own life cycle and input events and can add and remove from the activity while the activity is running. The fragment will always included in an activity and also known as sub-activity.

The life cycle of the fragment is directly affected by the lifecycle of the activity hosting the fragment.

All the fragment transactions will be move to the activity back-stack and the back button will be used to invoke the fragment transaction from the back stack.

By dividing the activity layout in multiple fragments, you can design a user interface with multiple views in one screen instead of using multiple activities.

For Example a activity could be divide into two fragments left as a list fragment and right as the details fragment to better navigate the contents in single screen. You should keep the design fragment design modular and reusable and avoid the manipulation of one fragment from another, this way you have a greater flexibility to reuse the fragments.