PLAYING WITH FRAGMENT

Android Lecture

OVERVIEW• Introduced with Honeycomb (API 11)• Modular section of an activity / Part of a user interface• More dynamic and flexible UI on large screens• Reusability across activities• Supported via Compatibility Package• Embedded in activities• Lives in a ViewGroup inside the activity’s view

hierarchy• Its own layout and behavior with its own life-cycle

WHEN TO USE?• Large screens - multi pane, flexible U• Combined with other UI widgets, ActionBar,

ViewPager, NavigationDrawer etc. - beautiful native app!

• More flexible, smooth, compact app with less activities. Multiple fragments in a single activity

USE CASE - TABLET VS HANDSET

LIFECYCLE

FRAGMENT MAGEMENT• FragmentManager to interact with fragments inside

an Activity• Activity.getFragmentManager()• android.support.v4.app.FragmentActivity.getSupportFragmen

tManager()

• FragmentTransaction to perform fragment operations : add, remove, replace, hide at run-time etc.

FRAGMENT COMMUNICATION• Fragment to Fragment communication via callbacks to

the Activity; inner type interfaces defined in fragments• Avoid tight coupling between activities and fragments• To access activity from fragment,

Fragment.getActivity()• To access fragment from activity

• FragmentManager.findFragmentById(int id)• FragmentManager.findFragmentByTag(String tag)

FRAGMENT COMMUNICATION• Fragment to fragment communication should be done

through Parent Activity• Create inner interface Listener

public interface OnItemClickListener{

public void onItemClick(int position);

}

FRAGMENT COMMUNICATION• Prepare the callback

OnItemClickListener callback;

public void onAttach(Activity activity) {

super.onAttach(activity);

try{

callback = (OnItemClickListener) activity;

}catch(ClassCastException e){

throw new ClassCastException(activity.toString() +

" must implements OnItemClickListener");

}

}

FRAGMENT COMMUNICATION• Trigger when needed

public void onListItemClick(ListView l, View v, int position, long id) {

super.onListItemClick(l, v, position, id);

callback.onItemClick(position);

}

FRAGMENT COMMUNICATION• Passing data to fragment

DetailFragment detailFragment = new DetailFragment();

Bundle bundle = new Bundle();

bundle.putInt("index", position);

detailFragment.setArguments(bundle);

FRAGMENT COMMUNICATION• Catch data from fragment

Bundle bundle = getArguments();

int index = 0;

if(bundle != null) index = bundle.getInt("index", 0);

FRAGMENT TRANSACTION• add - Add a fragment to the activity• remove - Remove an existing fragment; its view is

also removed• replace - Remove one fragment from the activity and

add another• hide - Hides an existing fragment; its view is hidden• show - Show previously hidden fragment

FRAGMENT TRANSACTION

FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();

transaction.add(R.id.main, detailFragment)

.addToBackStack(null)

.commit();

NESTED FRAGMENTFragment inside another fragment

FragmentTransaction transaction = detailFragment.getChildFragmentManager().beginTransaction();

transaction.add(R.id.detail, nestedFragment, "nested")

.addToBackStack(null)

.commit();

FRAGMENT BACKSTACK

A AB ABC

transaction.add(R.id.main, fragmentA).addToBackStack(“fragmentA”).commit();

transaction.add(R.id.main, fragmentB);

transaction.add(R.id.main, fragmentC);

FRAGMENT BACKSTACK

A AB ABC

getSupportFragmentManager(). popBackStack(“fragmentA”, 0);

getSupportFragmentManager(). popBackStackImmediate(“fragmentA”, 0);

OTHERS• DialogFragment• ViewPager• PreferenceFragment• Headless Fragment