Android Tutorial - Chapter 4 Fragments! (using support library)

P1_CreateFragment.java

// fragment = nested sub-activity w/ its own layout and lifecycle. (modular section of an activity)
// fragment receives the same lifecycle callbacks as its parent activity does
public class ArticleFragment extends Fragment {
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    return inflater.inflate(R.layout.article_view, container, false);
  }
}

P2_AddFragmentUsingXML.xml

<!-- res/layout-large/news_articles.xml -->
<!-- news article layout will have 2 fragments when the screen is large -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="horizontal"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  
  <fragment android:name="com.example.....fragments.HeadlinesFragment"
    android:id="@+id/headlines_fragment"/>  <!-- obmitting layout attrs -->
  
  <fragment android:name="com.example.....fragments.ArticleFragment"
    android:id="@+id/article_fragment"/>  <!-- obmitting layout attrs -->
    
</LinearLayout>

P2_ApplyingLayout.java

// < API 11 - extend FragmentActvity or ActionBarActivity (if using appcompat).
// >= API 11 - use Fragment class
public class MainActivity extends FragmentActivity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.news_article);
  }
}

P3_AddingFragmentAtRuntime.java

// dynamically adding fragments allows removal and replacement.

public class MainActivity extends FragmentActivity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.news_article);
    
    if (findViewById(R.id.fragment_container != null) {
      
      if (savedInstanceState != null) {
        return; // avoid duplicate
      }
      
      // handle intent if needed
      ArticleFragment frag = new ArticleFragment();
      frag.setArguments(getIntent().getExtras());
      
      getSupportFragmentManager().beginTransaction()
        .add(R.id.fragment_container, frag).commit();
    }
  }
}

P3_AddingFragmentAtRuntime.xml

// res/layout/news_article.xml
// Rule - Activity layout must include a container "VIew" in which the fragment is inserted.
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/fragment_container" />

P4_ReplaceFragment.java

// create
ArticleFragment newFrag - new ArticleFragment();
Bundle args = new Bundle();
args.putInt(ArticleFragment.ARG_POSITION, position);
newFrag.setArguments(bundle);

FragmentTransaction trx = getSupportFragmentManager().beginTransaction();

// replace!
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null); // add transaction itself to the back stack (allows for back btn navigation)

// commit
transaction.commit();

P5_InterFragCommunication.java

// frag to frag communication is done thru the associated activity. (NEVER directly)
puiblic class HeadlinesFragment extends ListFragment {
  OnHeadlineSelectedListener mCallback;
  
  // define interface to implement in the activity class
  public interface OnHeadlineSelectedListener {
    public void onArticleSelected(int position);
  }
  
  @Override
  public void onAttach(Activity activity) {
    super.onAttack(activity);
    
    try {
      mCallback = (OnHeadlineSelectedListener) activity;
    } catch (ClassCastException e) {
      throw new ClassCastException(activity.toString() + " must impplement OnHeadlineSelectedListener");
    }
  }
  
  @Override
  public void onListItemClick(ListView l, View v, int position, long id) {
    mCallback.onArticleSelected(position);
  }
}

/*
 * Activity
 */
public static class MainActivity extends Activity
  implements HeadlinesFragment.OnHeadlineSelectedListener {
  
  public void onArticleSelected(int pos) {
    // display something..
  }
}