fragment简介

1.添加用户界面

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

<?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="com.example.news.ArticleListFragment"
            android:id="@+id/list"
            android:layout_weight="1"
            android:layout_width="0dp"
            android:layout_height="match_parent" />
    <fragment android:name="com.example.news.ArticleReaderFragment"
            android:id="@+id/viewer"
            android:layout_weight="2"
            android:layout_width="0dp"
            android:layout_height="match_parent" />
</LinearLayout>

FragmentManager fragmentManager = getFragmentManager()
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

ExampleFragment fragment = new ExampleFragment();
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.commit();

3.添加没有 UI 的Fragment

管理Fragment

FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

// Create new fragment and transaction
Fragment newFragment = new ExampleFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();

// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);

// Commit the transaction
transaction.commit();

与 Activity 通信

View listView = getActivity().findViewById(R.id.list);

1.创建对 Activity 的事件回调

public static class FragmentA extends ListFragment {
    ...
    // Container Activity must implement this interface
    public interface OnArticleSelectedListener {
        public void onArticleSelected(Uri articleUri);
    }
    ...
}

public static class FragmentA extends ListFragment {
    OnArticleSelectedListener mListener;
    ...
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnArticleSelectedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement OnArticleSelectedListener");
        }
    }
    ...
}

public static class FragmentA extends ListFragment {
    OnArticleSelectedListener mListener;
    ...
    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        // Append the clicked item's row ID with the content provider Uri
        Uri noteUri = ContentUris.withAppendedId(ArticleColumns.CONTENT_URI, id);
        // Send the event and Uri to the host activity
        mListener.onArticleSelected(noteUri);
    }
    ...
}

2.向操作栏添加项目

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.fragment_layout);
}

<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>

<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>

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();
                if (index == 0) {
                    ft.replace(R.id.details, details);
                } else {
                    ft.replace(R.id.a_item, 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);
        }
    }
}

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;
    }
}

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();
        }
    }
}