android Fragments详解七:fragement示例

转自：http://blog.csdn.net/nkmnkm/article/details/7197255

 

 

例中实验了上面所讲的所有内容。此例有一个activity，其含有两个fragment。一个显示莎士比亚剧的播放曲目，另一个显示选中曲目的摘要。此例还演示了如何跟据屏幕大小配置fragment。

主activity创建layout。

 

@Override  protectedvoid onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);       setContentView(R.layout.fragment_layout);  }  

主activity的layoutxml文档

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"      android:orientation="horizontal"      android:layout_width="match_parent" android:layout_height="match_parent">        <fragment class="com.example.android.apis.app.FragmentLayout$TitlesFragment"              android:id="@+id/titles" android:layout_weight="1"              android:layout_width="0px" android:layout_height="match_parent" />        <FrameLayout android:id="@+id/details" android:layout_weight="1"              android:layout_width="0px" android:layout_height="match_parent"              android:background="?android:attr/detailsElementBackground" />    </LinearLayout>

系统在activity加载此layout时初始化TitlesFragment（用于显示标题列表），TitlesFragment的右边是一个FrameLayout，用于存放显示摘要的fragment，但是现在它还是空的，fragment只有当用户选择了一项标题后，摘要fragment才会被放到FrameLayout中。

然而，并不是所有的屏幕都有足够的宽度来容纳标题列表和摘要。所以，上述layout只用于横屏，现把它存放于ret/layout-land/fragment_layout.xml。

之外，当用于竖屏时，系统使用下面的layout，它存放于ret/layout/fragment_layout.xml：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"      android:layout_width="match_parent" android:layout_height="match_parent">      <fragment class="com.example.android.apis.app.FragmentLayout$TitlesFragment"              android:id="@+id/titles"              android:layout_width="match_parent" android:layout_height="match_parent" />  </FrameLayout>  

这个layout只包含TitlesFragment。这表示当使用竖屏时，只显示标题列表。当用户选中一项时，程序会启动一个新的activity去显示摘要，而不是加载第二个fragment。

下一步，你会看到Fragment类的实现。第一个是TitlesFragment，它从ListFragment派生，大部分列表的功能由ListFragment提供。

当用户选择一个Title时，代码需要做出两种行为，一种是在同一个activity中显示创建并显示摘要fragment，另一种是启动一个新的activity。

 

public static class TitlesFragment extends ListFragment {      boolean mDualPane;      int mCurCheckPosition = 0;        @Override      public void onActivityCreated(Bundle savedInstanceState) {          super.onActivityCreated(savedInstanceState);            // Populate list with our static array of titles.           setListAdapter(new ArrayAdapter<String>(getActivity(),                  android.R.layout.simple_list_item_activated_1, Shakespeare.TITLES));            // Check to see if we have a frame in which to embed the details           // fragment directly in the containing UI.           View detailsFrame = getActivity().findViewById(R.id.details);          mDualPane = detailsFrame != null && detailsFrame.getVisibility() == View.VISIBLE;            if (savedInstanceState != null) {              // Restore last state for checked position.               mCurCheckPosition = savedInstanceState.getInt("curChoice", 0);          }            if (mDualPane) {              // In dual-pane mode, the list view highlights the selected item.               getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);              // Make sure our UI is in the correct state.               showDetails(mCurCheckPosition);          }      }        @Override      public void onSaveInstanceState(Bundle outState) {          super.onSaveInstanceState(outState);          outState.putInt("curChoice", mCurCheckPosition);      }        @Override      public void onListItemClick(ListView l, View v, int position, long id) {          showDetails(position);      }        /**      * Helper function to show the details of a selected item, either by      * displaying a fragment in-place in the current UI, or starting a      * whole new activity in which it is displayed.      */      void showDetails(int index) {          mCurCheckPosition = index;            if (mDualPane) {              // We can display everything in-place with fragments, so update               // the list to highlight the selected item and show the data.               getListView().setItemChecked(index, true);                // Check what fragment is currently shown, replace if needed.               DetailsFragment details = (DetailsFragment)                      getFragmentManager().findFragmentById(R.id.details);              if (details == null || details.getShownIndex() != index) {                  // Make new fragment to show this selection.                   details = DetailsFragment.newInstance(index);                    // Execute a transaction, replacing any existing fragment                   // with this one inside the frame.                   FragmentTransaction ft = getFragmentManager().beginTransaction();                  ft.replace(R.id.details, details);                  ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);                  ft.commit();              }            } else {              // Otherwise we need to launch a new activity to display               // the dialog fragment with selected text.               Intent intent = new Intent();              intent.setClass(getActivity(), DetailsActivity.class);              intent.putExtra("index", index);              startActivity(intent);          }      }  

 

第二个fragment，DetailsFragment显示被选择的Title的摘要：

public static class DetailsFragment extends Fragment {      /**      * Create a new instance of DetailsFragment, initialized to      * show the text at 'index'.      */      public static DetailsFragment newInstance(int index) {          DetailsFragment f = new DetailsFragment();            // Supply index input as an argument.           Bundle args = new Bundle();          args.putInt("index", index);          f.setArguments(args);            return f;      }        public int getShownIndex() {          return getArguments().getInt("index", 0);      }        @Override      public View onCreateView(LayoutInflater inflater, ViewGroup container,              Bundle savedInstanceState) {          if (container == null) {              // We have different layouts, and in one of them this               // fragment's containing frame doesn't exist.  The fragment               // may still be created from its saved state, but there is               // no reason to try to create its view hierarchy because it               // won't be displayed.  Note this is not needed -- we could               // just run the code below, where we would create and return               // the view hierarchy; it would just never be used.               return null;          }            ScrollView scroller = new ScrollView(getActivity());          TextView text = new TextView(getActivity());          int padding = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,                  4, getActivity().getResources().getDisplayMetrics());          text.setPadding(padding, padding, padding, padding);          scroller.addView(text);          text.setText(Shakespeare.DIALOGUE[getShownIndex()]);          return scroller;      }  }  

 

如果当前的layout没有R.id.detailsView（它被用于DetailsFragment的容器），那么程序就启动DetailsActivity来显示摘要。

下面是DetailsActivity，它只是简单地嵌入DetailsFragment来显示摘要。

public static class DetailsActivity extends Activity {        @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);            if (getResources().getConfiguration().orientation                  == Configuration.ORIENTATION_LANDSCAPE) {              // If the screen is now in landscape mode, we can show the               // dialog in-line with the list so we don't need this activity.               finish();              return;          }            if (savedInstanceState == null) {              // During initial setup, plug in the details fragment.               DetailsFragment details = new DetailsFragment();              details.setArguments(getIntent().getExtras());              getFragmentManager().beginTransaction().add(android.R.id.content, details).commit();          }      }  }  

 

注意这个activity在检测到是竖屏时会结束自己，于是主activity会接管它并显示出TitlesFragment和DetailsFragment。这可以在用户在竖屏时显示在TitleFragment，但用户旋转了屏幕，使显示变成了横屏。