ViewPager 中 Fragment 上的 Fragment 不会在方向更改时重新加载

我正在开发一个使用 ActionBarSherlock 和 ViewPagerIndicator 的 Android 应用程序。主要活动是 SherlockFragmentActivity，用户通过操作栏上的选项卡在片段之间导航。所有选项卡都是 SherlockListFragments，并且大多数仅包含 ListView。但是，一个片段 (HeadlinesFragment) 包含 ViewPager、CirclePageIndicator 和平板电脑上的 ListView，而手机上仅包含 ListView。 ViewPager 有一个 FragmentStatePagerAdapter，它返回项目的 SherlockFragment。

问题是，在方向更改（或任何配置更改）时，ViewPager 内的子片段不会重新加载，并且 CirclePagerIndicator 不会显示任何指示器，就好像 ViewPager 为空一样。但是 ListView 确实会正确重新加载。在片段的初始加载时，ViewPager 可以正常工作，但在方向更改后就无法正常工作。

MainActivity.java

public class MainActivity extends SherlockFragmentActivity {
    // =============== Variable Declaration ================
    private HashMap<Integer, String> tabData;
    private HashMap<Integer, String> tabExtra;
    private Fragment currentFragment = null;
    private Fragment savedFragment = null;
    public ActionBar mActionBar;
    public MenuItem mRefresh;
    public static int mCurrentPos;

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

        HashMap<String, Object> savedData = (HashMap<String, Object>) getLastCustomNonConfigurationInstance();
        if (savedData != null) {
            tabData = (HashMap<Integer, String>) savedData.get("tabData");
            tabExtra = (HashMap<Integer, String>) savedData.get("tabExtra");
            savedFragment = (Fragment) savedData.get("currentFragment");
            mCurrentPos = ((Integer) savedData.get("pos")).intValue();
        } else {
            tabData = (HashMap<Integer, String>) getIntent().getExtras().getSerializable("tabData");
            tabExtra = (HashMap<Integer, String>) getIntent().getExtras().getSerializable("tabExtra");
            mCurrentPos = 0;
        }

        mActionBar = getSupportActionBar();
        Const.IsTablet = Utils.isTablet(MainActivity.this);
        //if (!Const.IsTablet) setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

        TypedArray tabs = getResources().obtainTypedArray(R.array.TabBars);
        Tab tab;
        for (int i = 0; i < tabs.length(); i++) {
            String tabInfo[] = getResources().getStringArray(tabs.getResourceId(i, 0));
            tab = mActionBar.newTab().setText(tabInfo[1]);

            if (tabInfo[0].equalsIgnoreCase("customizedNewsPage")) {
                tab.setTabListener(new MainTabListener<HeadlinesFragment>(MainActivity.this, i, HeadlinesFragment.class));
            }
            mActionBar.addTab(tab);
        }
        tabs.recycle();
        mActionBar.selectTab(mActionBar.getTabAt(mCurrentPos));
        mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        //set navbar for ICS+ devices
        mActionBar.setBackgroundDrawable(getResources().getDrawable(R.drawable.navbar));
    }

    @SuppressLint("HandlerLeak")
    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message message) {
            Bundle bundle = message.getData();
            if (bundle.getInt("result") == Activity.RESULT_OK && bundle.getString("data") != null) {
                tabData.put(Integer.valueOf(bundle.getInt("tabPos")), bundle.getString("data"));
                DataType type = DataType.values()[bundle.getInt("type")];
                switch (type) {
                    case Headlines:
                        ((HeadlinesFragment) currentFragment).setData(bundle.getString("data"));
                        break;
                }
                tabData.put(Integer.valueOf(bundle.getInt("tabPos")), bundle.getString("data"));
                setRefreshActionButtonState(false);
            }
        }
    };

    public Handler getHandler() {
        return mHandler;
    }

    @Override
    public Object onRetainCustomNonConfigurationInstance() {
        final HashMap<String, Object> savedData = new HashMap<String, Object>();
        savedData.put("currentFragment", currentFragment);
        savedData.put("tabData", tabData);
        savedData.put("tabExtra", tabExtra);
        savedData.put("pos", Integer.valueOf(mCurrentPos));
        return savedData;
    }

    private class MainTabListener<T extends Fragment> implements TabListener {
        private Fragment mFragment;
        private final SherlockFragmentActivity mActivity;
        private final int mPos;
        private final Class<T> mClass;

        /** Constructor used each time a new tab is created. */
        public MainTabListener(SherlockFragmentActivity activity, int pos, Class<T> clz) {
            mActivity = activity;
            mPos = pos;
            mClass = clz;
        }

        @Override
        public void onTabSelected(Tab tab, FragmentTransaction ignoredFt) {
            FragmentManager fragMgr = ((FragmentActivity) mActivity).getSupportFragmentManager();
            FragmentTransaction ft = fragMgr.beginTransaction();

            // Check if the fragment is already initialized
            if (mFragment == null) {
                // If not, instantiate and add it to the activity
                mFragment = Fragment.instantiate(mActivity, mClass.getName());

                Bundle args = new Bundle();
                args.putString("data", tabData.get(mPos));
                args.putInt("pos", mPos);
                mFragment.setArguments(args);

                ft.add(android.R.id.content, mFragment);
            } else {
                ft.attach(mFragment);
            }
            currentFragment = mFragment;
            mCurrentPos = mPos;
            mRefresh = null;

            ft.commit();
        }

        @Override
        public void onTabUnselected(Tab tab, FragmentTransaction ignoredFt) {
            FragmentManager fragMgr = ((FragmentActivity) mActivity).getSupportFragmentManager();
            FragmentTransaction ft = fragMgr.beginTransaction();

            fragMgr.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);

            // Check if the fragment is already initialized
            if (mFragment == null) {
                mFragment = SherlockFragment.instantiate(mActivity, mClass.getName());
                ft.add(android.R.id.content, mFragment);
            } else {
                ft.detach(mFragment);
            }
            currentFragment = null;

            ft.commit();
        }

        @Override
        public void onTabReselected(Tab tab, FragmentTransaction ignoredFt) {
            onTabUnselected(tab, ignoredFt);
            onTabSelected(tab, ignoredFt);
        }
    }
}

HeadlinesFragment.java

public class HeadlinesFragment extends SherlockListFragment implements SearchView.OnQueryTextListener, SearchView.SearchViewChangeMode, OnItemClickListener {
    private static final String LOG_TAG = "Headlines Fragment";
    private JSONArray mHeadlines = new JSONArray();
    private JSONArray mHeadlinesTop = new JSONArray();
    private SearchView mSearchView;
    private MenuItem mSearchItem;
    private ViewPager mPager;
    private CirclePageIndicator mIndicator;
    private static int mPos;
    private int mRotatorImageWidth;
    private static HeadlinesFragment instance;
    private Tracker tracker;
    private Timer refreshTimer;
    private int refreshTime = 0;;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
        instance = this;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        mPos = getArguments().getInt("pos");
        TypedArray tabs = getResources().obtainTypedArray(R.array.TabBars);
        String tabInfo[] = getResources().getStringArray(tabs.getResourceId(mPos, 0));
        mRotatorImageWidth = Integer.valueOf(tabInfo[7]).intValue();
        refreshTime = Integer.valueOf(tabInfo[4]).intValue();
        tabs.recycle();

        try {
            mHeadlines = new JSONArray(getArguments().getString("data"));
        } catch (NotFoundException e) {
            Log.e(LOG_TAG, "Error loading data", e);
        } catch (JSONException e) {
            Log.e(LOG_TAG, "Error loading data", e);
        }

        return inflater.inflate(R.layout.activity_headlines, container, false);
    }

    @SuppressWarnings("deprecation")
    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        //if (Const.IsTablet) {
        if (((SIDHelpApplication) getActivity().getApplicationContext()).isTablet()) {
            try {
                mHeadlinesTop = new JSONArray();
                JSONArray temp = new JSONArray();
                for (int i = 0; i < mHeadlines.length(); i++) {
                    if (i < 5) {
                        mHeadlinesTop.put(mHeadlines.get(i));
                    } else {
                        temp.put(mHeadlines.get(i));
                    }
                }
                mHeadlines = temp;
            } catch (JSONException e) {
                Log.e(LOG_TAG, "Error splitting off top 5", e);
            }

            mPager = (ViewPager) getActivity().findViewById(R.id.rotator);
            mPager.setOffscreenPageLimit(4);
            mPager.setAdapter(new RotatorAdapter(this, getActivity(), mHeadlinesTop, mRotatorImageWidth, mPos));
            if (getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {
                mPager.getLayoutParams().height = (int) Math.floor((((float) getResources().getInteger(R.integer.NewsImageHeight) / (float) getResources().getInteger(R.integer.NewsImageWidth)) *  (float) getActivity().getWindowManager().getDefaultDisplay().getWidth()));
            }

            mIndicator = (CirclePageIndicator) getActivity().findViewById(R.id.indicator);
            mIndicator.setViewPager(mPager);
        }

        setListAdapter(new HeadlinesAdapter(getSherlockActivity(), mHeadlines));
        getListView().setOnItemClickListener(this);
        getListView().setEmptyView(getActivity().findViewById(android.R.id.empty));
        setAutoRefresh();
    }

    public void setData(String data) {
        setData(data, false);
    }

    public void setData(String data, boolean search) {
        try {
            mHeadlines = new JSONArray(data);
            if (((SIDHelpApplication) getActivity().getApplicationContext()).isTablet() && !search) {
                mHeadlinesTop = new JSONArray();
                try {
                    JSONArray temp = new JSONArray();
                    for (int i = 0; i < mHeadlines.length(); i++) {
                        if (i < 5) {
                            mHeadlinesTop.put(mHeadlines.get(i));
                        } else {
                            temp.put(mHeadlines.get(i));
                        }
                    }
                    mHeadlines = temp;
                } catch (JSONException e) {
                    Log.e(LOG_TAG, "Error splitting off top 5", e);
                }

                ((RotatorAdapter) mPager.getAdapter()).setData(mHeadlinesTop);
                mPager.setVisibility(View.VISIBLE);
                mIndicator.setVisibility(View.VISIBLE);
            } else {
                getActivity().findViewById(android.R.id.empty).setVisibility(View.GONE);
            }

            if (search && mPager != null) {
                mPager.setVisibility(View.GONE);
                mIndicator.setVisibility(View.GONE);
            }

            ((HeadlinesAdapter) getListAdapter()).setData(mHeadlines);
            setAutoRefresh();
        } catch (JSONException e) {
            Log.e(LOG_TAG, "Setting Data", e);
        }
    }

    public static HeadlinesFragment getInstance() {
        return instance;
    }
}

活动标题.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/llMainHeadline"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:focusable="false"
    android:focusableInTouchMode="true"
    android:background="@drawable/bg_img" >

    <android.support.v4.view.ViewPager
        android:id="@+id/rotator"
        android:layout_width="match_parent"
        android:layout_height="@dimen/headlines_rotator_height"
        android:layout_alignParentTop="true"
        android:background="@android:color/black" />

    <com.viewpagerindicator.CirclePageIndicator
        android:id="@+id/indicator"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/rotator"
        android:background="@android:color/black"
        android:padding="10dp" />

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentBottom="true"
        android:layout_below="@id/indicator"
        android:cacheColorHint="#00000000"
        android:listSelector="@color/TableCellSelection" />

    <TextView
        android:id="@android:id/empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="@string/noResults"
        android:textSize="@dimen/noResult_text_size"
        android:textStyle="bold"
        android:visibility="gone" />

</RelativeLayout>

旋转适配器.java

public class RotatorAdapter extends FragmentStatePagerAdapter {
    private static final String LOG_TAG = "Rotator Adapter";
    private Context mContext;
    private JSONArray mData;
    private int mImageWidth;
    private int mPos;

    public RotatorAdapter(SherlockListFragment fragment, Context context, JSONArray data, int imageWidth, int pos) {
        super(fragment.getChildFragmentManager());
        mContext = context;
        mData = data;
        mImageWidth = imageWidth;
        mPos = pos;
    }

    @Override
    public int getCount() {
        return mData.length();
    }

    @Override
    public Fragment getItem(int pos) {
        Fragment fragment = null;
        Bundle args = new Bundle();
        try {
            JSONObject hdata = mData.getJSONObject(pos);
            args.putString("title", hdata.getString(mContext.getResources().getString(R.string.tag_title)));
            args.putString("category", hdata.getString(mContext.getResources().getString(R.string.tag_category)));
            args.putString("time", hdata.getString(mContext.getResources().getString(R.string.tag_time)));
            args.putString("newsID", hdata.getString(mContext.getResources().getString(R.string.tag_newsID)));
            args.putString("photoURL", hdata.getString(mContext.getResources().getString(R.string.tag_photoURL)));
            args.putInt("imageWidth", mImageWidth);
            args.putInt("pos", mPos);
            fragment = Fragment.instantiate(mContext, RotatorFragment.class.getName(), args);
        } catch (JSONException e) {
            Log.e(LOG_TAG, "Error getting data", e);
        }

        return fragment;
    }

    public void setData(JSONArray data) {
        mData = data;
        notifyDataSetChanged();
    }
}

RotatorFragment.java

public class RotatorFragment extends SherlockFragment implements OnClickListener {
    private static final String LOG_TAG = "Rotator Fragment";
    private String mNewsID;
    private int mPos;
    private ImageLoader imageLoader = ImageLoader.getInstance();

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.activity_headlines_top_row, container, false);

        // Set the image
        ImageView image = (ImageView) view.findViewById(R.id.imgArticle);
        String photoURL = getArguments().getString("photoURL").replaceAll(" ", "%20");
        imageLoader.displayImage(photoURL, image);

        // Set title, category, and time
        TextView headlineTitle = (TextView) view.findViewById(R.id.txtTitle);
        TextView headlineCategory = (TextView) view.findViewById(R.id.txtCategory);
        headlineTitle.setText(getArguments().getString("title"));
        headlineCategory.setText(String.format("%s - %s", getArguments().getString("category"), getArguments().getString("time")));

        // Set article ID for onclick listener
        mNewsID = getArguments().getString("newsID");
        mPos = getArguments().getInt("pos");
        view.setOnClickListener(this);
        return view;
    }

    @Override
    public void onClick(View v) {
        // Load article data
        Log.i(LOG_TAG, "Loading Article");
        Intent dataIntent = new Intent(getActivity(), DataLoader.class);
        Messenger dataMessenger = new Messenger(HeadlinesFragment.mHandler);
        dataIntent.putExtra("MESSENGER", dataMessenger);
        dataIntent.putExtra("tabPos", mPos);
        dataIntent.putExtra("type", DataType.HeadlinesArticle.ordinal());
        String params[] = new String[] {mNewsID};
        dataIntent.putExtra("params", params);
        getActivity().startService(dataIntent);
    }

    @Override
    public void onSaveInstanceState (Bundle outState) {
        // Don't save the fragment state
    }
}

我想通了这个问题。问题是当配置更改时，Android 会销毁并重新创建 Activity，但 Fragments 不会被销毁。它们被添加回管理器，并且由于代码也被重新创建。因此，创建新 Fragment 时未重新创建的 ViewPager 未正确引用它。解决这个问题的方法是在 onTabSelected 函数中，我检查了管理器中已存在的片段，然后使用它而不是重新创建它。我还必须向创建的每个片段添加标签，以便我可以找到我正在寻找的片段。

if (mCurrentTag != null && mCurrentTag.equalsIgnoreCase(mTag) && fragMgr.findFragmentByTag(mCurrentTag) != null) {
    mFragment = fragMgr.findFragmentByTag(mCurrentTag);
}