问ViewPager和片段 - 存储片段状态的正确方法是什么？

public class DashboardActivity extends BasePagerActivity implements OnMessageListActionListener {

private MessagesFragment mMessagesFragment;

@Override

protected void onCreate(Bundle savedInstanceState) {

    Logger.d("Dash onCreate");

    super.onCreate(savedInstanceState);

    setContentView(R.layout.viewpager_container);

    new DefaultToolbar(this);

    // create fragments to use

    mMessagesFragment = new MessagesFragment();

    mStreamsFragment = new StreamsFragment();

    // set titles and fragments for view page

    Map<String, Fragment> screens = new LinkedHashMap<String, Fragment>();

    screens.put(getApplicationContext().getString(R.string.dashboard_title_dumb), new DumbFragment());

    screens.put(getApplicationContext().getString(R.string.dashboard_title_messages), mMessagesFragment);

    // instantiate view pager via adapte

    mPager = (ViewPager) findViewById(R.id.viewpager_pager);

    mPagerAdapter = new BasePagerAdapter(screens, getSupportFragmentManager());

    mPager.setAdapter(mPagerAdapter);

    // set title indicato

    TitlePageIndicator indicator = (TitlePageIndicator) findViewById(R.id.viewpager_titles);

    indicator.setViewPager(mPager, 1);

}

/* set of fragments callback interface implementations */

@Override

public void onMessageInitialisation() {

    Logger.d("Dash onMessageInitialisation");

    if (mMessagesFragment != null)

        mMessagesFragment.loadLastMessages();

}

@Override

public void onMessageSelected(Message selectedMessage) {

    Intent intent = new Intent(this, StreamActivity.class);

    intent.putExtra(Message.class.getName(), selectedMessage);

    startActivity(intent);

}

public class BasePagerActivity extends FragmentActivity {

BasePagerAdapter mPagerAdapter;

ViewPager mPager;

}

public class BasePagerAdapter extends FragmentPagerAdapter implements TitleProvider {

private Map<String, Fragment> mScreens;

public BasePagerAdapter(Map<String, Fragment> screenMap, FragmentManager fm) {

    super(fm);

    this.mScreens = screenMap;

}

@Override

public Fragment getItem(int position) {

    return mScreens.values().toArray(new Fragment[mScreens.size()])[position];

}

@Override

public int getCount() {

    return mScreens.size();

}

@Override

public String getTitle(int position) {

    return mScreens.keySet().toArray(new String[mScreens.size()])[position];

}

// hack. we don't want to destroy our fragments and re-initiate them afte

@Override

public void destroyItem(View container, int position, Object object) {

    // TODO Auto-generated method stub

}

}

public class MessagesFragment extends ListFragment {

private boolean mIsLastMessages;

private List<Message> mMessagesList;

private MessageArrayAdapter mAdapter;

private LoadMessagesTask mLoadMessagesTask;

private OnMessageListActionListener mListener;

// define callback interface

public interface OnMessageListActionListener {

    public void onMessageInitialisation();

    public void onMessageSelected(Message selectedMessage);

}

@Override

public void onAttach(Activity activity) {

    super.onAttach(activity);

    // setting callback

    mListener = (OnMessageListActionListener) activity;

    mIsLastMessages = activity instanceof DashboardActivity;

}

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    inflater.inflate(R.layout.fragment_listview, container);

    mProgressView = inflater.inflate(R.layout.listrow_progress, null);

    mEmptyView = inflater.inflate(R.layout.fragment_nodata, null);

    return super.onCreateView(inflater, container, savedInstanceState);

}

@Override

public void onActivityCreated(Bundle savedInstanceState) {

    super.onActivityCreated(savedInstanceState);

    // instantiate loading task

    mLoadMessagesTask = new LoadMessagesTask();

    // instantiate list of messages

    mMessagesList = new ArrayList<Message>();

    mAdapter = new MessageArrayAdapter(getActivity(), mMessagesList);

    setListAdapter(mAdapter);

}

@Override

public void onResume() {

    mListener.onMessageInitialisation();

    super.onResume();

}

public void onListItemClick(ListView l, View v, int position, long id) {

    Message selectedMessage = (Message) getListAdapter().getItem(position);

    mListener.onMessageSelected(selectedMessage);

    super.onListItemClick(l, v, position, id);

}

/* public methods to load messages from host acitivity, etc... */

}

    @Override

protected void onSaveInstanceState(Bundle outState) {

    super.onSaveInstanceState(outState);

    getSupportFragmentManager()

            .putFragment(outState, MessagesFragment.class.getName(), mMessagesFragment);

}

protected void onCreate(Bundle savedInstanceState) {

    Logger.d("Dash onCreate");

    super.onCreate(savedInstanceState);

    ...

    // create fragments to use

    if (savedInstanceState != null) {

        mMessagesFragment = (MessagesFragment) getSupportFragmentManager().getFragment(

                savedInstanceState, MessagesFragment.class.getName());

                StreamsFragment.class.getName());

    }

    if (mMessagesFragment == null)

        mMessagesFragment = new MessagesFragment();

    ...

}