[程式] Android Topic - Fragment

1. Create the fragments' layout
   ex.
   fragment A with red background - layout/A.xml
   fragment B with green background - layout/B.xml
2. Create the classes of fragments to add UI
   

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

   where <fragment's layout> is the fragment's layout filename. ex. A.xml or B.xml
3. Add fragment(s) to an activity
• Declare in layout file (XML)
  (For large device use,) create another layout file (in directory "layout-large") in which the fragment(s) would be shown. ex. home.xml
  

  <?xml version="1.0" encoding="utf-8"?>
  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="horizontal"
      android:layout_width="match_parent"
      android:layout_height="match_parent">
      <fragment
              android:name="sowhat.practice.fragment.fragmentA"
              android:id="@+id/list"
              android:layout_weight="1"
              android:layout_width="0dp"
              android:layout_height="match_parent" />
      <fragment 
              android:name="sowhat.practice.fragment.fragmentB"
              android:id="@+id/viewer"
              android:layout_weight="2"
              android:layout_width="0dp"
              android:layout_height="match_parent" />
  </LinearLayout>

  where android:name specifies the fragment class to instantiate the layout in the form <package>.<class>
• Programmatically add the fragment to an existing ViewGroup.
  "If your activity allows the fragments to be removed and replaced, you should add the initial fragment(s) to the activity during the activity's onCreate() method."
  "the fragment must have a container View in the layout in which the fragment's layout will reside."
• Create a layout file with FrameLayout inside
  In order to replace one fragment with another, the activity's layout includes an empty FrameLayout that acts as the fragment container. (For small device use,) create another layout file (in directory "layout") in which the fragment would be shown. (the name of this layout file should be the same with the one in layout-large. ie. home.xml)

• <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:id="@+id/fragment_container"
      android:layout_width="match_parent"
      android:layout_height="match_parent" />

• Set up in onCreate() of MainActivity

• public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.news_articles);
  
          if (findViewById(R.id.fragment_container) != null) {
  
              if (savedInstanceState != null) {
                  return;
              }
  
              fragmentA firstFragment = new FragmentA();
              
              firstFragment.setArguments(getIntent().getExtras());
              
              getSupportFragmentManager().beginTransaction()
                      .add(R.id.fragment_container, firstFragment).commit();
          }
      }

REF:
http://developer.android.com/training/basics/fragments/index.html
http://developer.android.com/guide/components/fragments.html