android Fragments详解七:fragement示例

最新推荐文章于 2021-05-29 11:08:49 发布

xuhuan_wh

最新推荐文章于 2021-05-29 11:08:49 发布

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分类专栏： android android界面相关 android Fragments 文章标签： Fragment

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下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();  
        }  
    }  
}