Content Providers与Fragment

public class LocalProvider extends ContentProvider {
    private static final String TAG = "LocalProvider";

    private SQLiteOpenHelper mOpenHelper;

    private static final int DATA = 1;
    private static final int DATA_ID = 2;
    private static final UriMatcher sURLMatcher = new UriMatcher(
            UriMatcher.NO_MATCH);

    static {
        sURLMatcher.addURI("*", "data", DATA);
        sURLMatcher.addURI("*", "data/#", DATA_ID);
    }

    private static class DatabaseHelper extends SQLiteOpenHelper {
        private static final String DATABASE_NAME = "local.db";
        private static final int DATABASE_VERSION = 1;

        public DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL("CREATE TABLE data (" +
                       "_id INTEGER PRIMARY KEY," +
                       "text TEXT, " +
                       "integer INTEGER);");

            // insert alarms
            db.execSQL("INSERT INTO data (text, integer) VALUES ('first data', 100);");
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int currentVersion) {
            Log.w(TAG, "Upgrading test database from version " +
                  oldVersion + " to " + currentVersion +
                  ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS data");
            onCreate(db);
        }
    }

    public LocalProvider() {
    }

    @Override
    public boolean onCreate() {
        mOpenHelper = new DatabaseHelper(getContext());
        return true;
    }

    @Override
    public Cursor query(Uri url, String[] projectionIn, String selection,
            String[] selectionArgs, String sort) {
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

        // Generate the body of the query
        int match = sURLMatcher.match(url);
        switch (match) {
            case DATA:
                qb.setTables("data");
                break;
            case DATA_ID:
                qb.setTables("data");
                qb.appendWhere("_id=");
                qb.appendWhere(url.getPathSegments().get(1));
                break;
            default:
                throw new IllegalArgumentException("Unknown URL " + url);
        }

        SQLiteDatabase db = mOpenHelper.getReadableDatabase();
        Cursor ret = qb.query(db, projectionIn, selection, selectionArgs,
                              null, null, sort);

        if (ret == null) {
            if (false) Log.d(TAG, "Alarms.query: failed");
        } else {
            ret.setNotificationUri(getContext().getContentResolver(), url);
        }

        return ret;
    }

    @Override
    public String getType(Uri url) {
        int match = sURLMatcher.match(url);
        switch (match) {
            case DATA:
                return "vnd.android.cursor.dir/vnd.google.unit_tests.local";
            case DATA_ID:
                return "vnd.android.cursor.item/vnd.google.unit_tests.local";
            default:
                throw new IllegalArgumentException("Unknown URL");
        }
    }

    @Override
    public int update(Uri url, ContentValues values, String where, String[] whereArgs) {
        int count;
        long rowId = 0;
        int match = sURLMatcher.match(url);
        SQLiteDatabase db = mOpenHelper.getWritableDatabase();
        switch (match) {
            case DATA_ID: {
                String segment = url.getPathSegments().get(1);
                rowId = Long.parseLong(segment);
                count = db.update("data", values, "_id=" + rowId, null);
                break;
            }
            default: {
                throw new UnsupportedOperationException(
                        "Cannot update URL: " + url);
            }
        }
        if (false) Log.d(TAG, "*** notifyChange() rowId: " + rowId);
        getContext().getContentResolver().notifyChange(url, null);
        return count;
    }


    @Override
    public Uri insert(Uri url, ContentValues initialValues) {
        return null;
    }

    @Override
    public int delete(Uri url, String where, String[] whereArgs) {
        throw new UnsupportedOperationException("delete not supported");
    }
}

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();

// 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();

@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() > 0) {
        getFragmentManager().popBackStack();
    } else {
        super.onBackPressed();
    }
}

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

ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment);

public static class FragmentA extends ListFragment {
    OnArticleSelectedListener mListener;

    // Container Activity must implement this interface
    public interface OnArticleSelectedListener {
        public void onArticleSelected(Uri articleUri);
    }
    ...
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnArticleSelectedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement OnArticleSelectedListener");
        }
    }
    ...
}