java - 使用选项卡和 onTabSelected() 时如何在 fragment 之间传递数据？

Question

这个tutorial指的是 fragment 之间的通信，但不用于选项卡。我想在我的“Daycare” fragment (它是一个选项卡)和我的“You” fragment (它也是一个选项卡)之间发送数据。我已经被这个问题困住了一个星期了。我真的不知道如何将接口(interface)的概念与 android 选项卡式 fragment 和来自 asynctasks 的数据结合起来。

我在我的 Daycare fragment 中创建了一个界面。我想借助“passparam”方法将字符串“daycarename”发送到“you” fragment 。据我了解，它需要以某种方式通过实现我的 TabClickedListener 接口(interface)的 MainActivity。如何将它从 MainActivity 传递回另一个 fragment ？

public class MainActivity extends Activity implements ActionBar.TabListener, DaycareFragment.TabClickedListener {

    SectionsPagerAdapter mSectionsPagerAdapter;
    ViewPager mViewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        mSectionsPagerAdapter = new SectionsPagerAdapter(getFragmentManager(), this);

        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

         mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                actionBar.setSelectedNavigationItem(position);
            }
        });

         for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            actionBar.addTab(
                actionBar.newTab()
                    .setText(mSectionsPagerAdapter.getPageTitle(i))
                    .setTabListener(this));
        }
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
        mViewPager.setCurrentItem(tab.getPosition());
    }

   public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {

        super(fm);
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:

                return new YouFragment();
            case 1:

                return new DaycareFragment();
            case 2:

                return new ThirdFragment();

        }

        return null;
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        Locale l = Locale.getDefault();
        switch (position) {
            case 0:
                return getString(R.string.title_section3).toUpperCase(l);
            case 1:
                return getString(R.string.title_section1).toUpperCase(l);
            case 2:
                return getString(R.string.title_section2).toUpperCase(l);

        }
        return null;
    }
}

    public class MainFragment extends Fragment {

        private static final String ARG_SECTION_TYPE = "section type";

        public MainFragment(){}

        public MainFragment(int sectionNumber) {
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_TYPE, sectionNumber);
            setArguments(args);
        }

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

            //setup the view
            switch(getArguments().getInt(ARG_SECTION_TYPE)) {
                //hide or show fields based on page number.
            }

            return rootView;
        }
    }
    @Override
    public void passParam(String var) {
        Toast.makeText(this, "Clicked " + var, Toast.LENGTH_LONG).show();

    }
}

我正在 ListFragment 中实现一个接口(interface):

public class DaycareFragment extends ListFragment {

    TabClickedListener listener;

    public interface TabClickedListener {
        public void passParam(String var);
    }
String email;
    UserFunctions userFunctions;
    Boolean owner;
@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_daycare, container, false);
        movies = new ArrayList<HashMap<String, String>>();

        userFunctions = new UserFunctions();
        HashMap map = new HashMap();
        map = userFunctions.getdauser(getActivity());
        email = (String) map.get("email");

        new GetDaDaycares().execute();

        return rootView;
    }
class GetDaDaycares extends AsyncTask<String, String, String>{

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

        }


        @Override
        protected String doInBackground(String... args) {

            String city = "london";
            try {

                List<NameValuePair> params = new ArrayList<NameValuePair> ();
                params.add(new BasicNameValuePair("city", city));

                @SuppressWarnings("unused")
                JSONObject json = parser.makeHttpRequest(getdaycare, params);
                jArray = json.getJSONArray("lTable");

                for (int i =0; i<jArray.length();i++){

                    JSONObject c = jArray.getJSONObject(i);
                    String daycarename = c.getString("daycarename");

                    HashMap<String, String> map = new HashMap<String, String>();
                    map.put("daycarename", daycarename);
                    movies.add(map);

                }

            } catch(JSONException e) {

                e.printStackTrace();
            }
            return null;

        }

        protected void onPostExecute(String zoom){
            pDialog.dismiss();

            getActivity().runOnUiThread(new Runnable() {
                public void run() {


                    ListAdapter adapter = new SimpleAdapter(getActivity(), movies,
                            R.layout.list, new String[] {"daycarename"},
                            new int[]{R.id.textView1});

                    setListAdapter(adapter);
                    ListView lv = getListView();
                    lv.setOnItemClickListener(new OnItemClickListener(){

                        @Override
                        public void onItemClick(AdapterView<?> parent, View view, int position,
                                                long id) {

                            String daycarename =movies.get(position).get("daycarename");

                        }

                    });


                }
            });
        }

    }

}

Answer 1

如果这是我的问题(确实如此)，我会有一个中央对象负责在 fragment 之间“共享”数据。

实现通常似乎遵循两条路径之一:一，创建一个任何对象都可以获取其实例的单例，或者二， Activity 初始化对象的单个实例，并在初始化时将其传递给每个 fragment 。

然后， fragment (或 AsyncTask)将通过观察者模式或显示方式更新并从该中心对象中提取数据，无论您想要什么。

附:如果您要在 fragment 中包含 AsyncTask，您将需要实现一种策略来确保您的 UI 在完成时不会死掉。否则你可以抛出异常。

p.p.sonPostExecute 默认在 UI 线程上运行。