FragmentManager

A fragment manager with several enchancements over the original one:

• shared element transitions on all APIs
• fragment pooling
• annotation-based fragment construction
• easy route building and execution
• support for both upstack and backstack
• fragment locking durning changes
• fragment tree debugger view
• no need to call super.on*() methods
• passing data between fragments (like startActivityForResult())
• custom animations for all state changes
• easy state saving for fields

The lifecycle:

• create (fragment is ready to use)
• restore (only if state is not null)
• attach (fragment's view is attached and laid out)
• start (activity is started)
• resume (activity is resumed, fragment is not animating)
• save
• pause
• stop
• detach
• destroy

A sample main fragment

@FragmentAnnotation(layout = R.layout.fragment_main)
public class MainFragment extends Fragment {

    @Override
    protected void onCreate() {
        if (getState() == null) { // this fragment is not being restored
            add(ContentFragment.class, R.id.container, TransactionMode.Join);
            add(DrawerFragment.class, R.id.drawer, TransactionMode.Join);
        }
    }
}

A sample activity with support for navigation with FragmentRoute

public class MainActivity extends FragmentActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (savedInstanceState == null)
            getFragmentManager2().add(MainFragment.class, R.id.root, TransactionMode.Join);
    }

    @Override
    protected boolean onNavigate(Fragment fragment, TransactionMode mode) {
        getFragmentManager2().replace(fragment, R.id.root, mode);
        return true;  // navigation was handled by me
    }
}

Saving and restoring fragment's state

For example let's pick a random background color and remember it.

private int color;

@Override
protected void onCreate() {
    View view = getView();

    if (getState() == null) { // is it a fresh fragment?
        int[] colors = {Color.RED, Color.BLUE, Color.GRAY, Color.BLACK, Color.YELLOW, Color.GREEN};
        color = colors[new Random().nextInt(colors.length)];
        view.setBackgroundColor(color);
    } else {
        color = getState().getInt(COLOR);
        view.setBackgroundColor(color);
    }
}

@Override
protected Bundle onSaveState() {
    Bundle state = new Bundle();
    state.putInt(COLOR, color);
    return state;
}

Shared element transition

Let's create and execute a transition between two fragments. The transition should animate two shared elements - an image and a title.

DetailFragment detailFragment = Fragment.instantiate(DetailFragment.class, getActivity());
FragmentTransaction transaction = new FragmentTransaction(getManager(), TransactionMode.Push);
transaction.replace(detailFragment, R.id.container);
transaction.addSharedElement(new ViewSharedElement(findViewById(R.id.image), this, detailFragment));
transaction.addSharedElement(new TextViewSharedElement(findViewById(R.id.title), this, detailFragment));
transaction.execute();

Pass data between fragments

Start a fragment with setTargetFragment()

// MainFragment
DetailFragment detailFragment = Fragment.instantiate(DetailFragment.class, getActivity());
add(detailFragment, R.id.container, TransactionMode.Add);

Return data using setResult()

// DetailFragment
int data = 5;
Bundle bundle = new Bundle();
bundle.putInt("data", data);
setResult(bundle);
getManager().back();

Save data using annotation

Simple data can be automatically saved and restored using @State annotation.

@State
int data;

This annotation can use setters as well. Simply keep the good, old Java naming convention.

@State
String title;

private void setTitle(String title){
    this.title = title;
    getToolbar().setTitle(title);
}