交换选项卡时未获取数据

Question

我已经实现了一个应用程序，其中有 7 个选项卡，当用户滚动列表时，我使用 addOnScrollListener 来获取数据。我的问题是当我将一个fragment 或标签移动到另一个fragment 然后返回到之前的标签时，数据不会第二次出现在该标签上。

下面是我的片段类

public class EI_Pending_Fragment extends Fragment{
SessionManager session;

private List<SuperHero> listSuperHeroes;
private RecyclerView recyclerView;
private RecyclerView.LayoutManager layoutManager;
private RecyclerView.Adapter adapter;
public ProgressBar progressBar;
private RequestQueue requestQueue;
private int requestCount1 = 1;
private Boolean isStarted = false;
private Boolean isVisible = false;
public String email;

public EI_Pending_Fragment() {}


@Override
public void onStart() {
    super.onStart();
    isStarted = true;
    if (isVisible && isStarted){
        getData();
    }
}

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    isVisible = isVisibleToUser;
    if (isStarted && isVisible) {
        getData();
    }
}


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

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

    session = new SessionManager(getActivity());
    // get user data from session
    HashMap<String, String> user = session.getUserDetails();
    email = user.get(SessionManager.KEY_EMAIL);
    return view;
}

public void onViewCreated(View v, Bundle savedInstanceState) {
    super.onViewCreated(v, savedInstanceState);

    recyclerView = (RecyclerView) v.findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(getContext());
    recyclerView.setLayoutManager(layoutManager);
    listSuperHeroes = new ArrayList<>();
    requestQueue = Volley.newRequestQueue(getContext());
    //   getData();
    adapter = new CardAdapter(listSuperHeroes, getActivity());
    recyclerView.setAdapter(adapter);
    progressBar = (ProgressBar) v.findViewById(R.id.progressBar1);

    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int
                newState) {
            super.onScrollStateChanged(recyclerView, newState);
            if (isLastItemDisplaying(recyclerView)) {
                if(requestCount1==1){
                    exit();
                }
                else {
                    getData();
                }
            }
        }
    });
}

private JsonArrayRequest getDataFromServer(int requestCount) {
    Log.e("email",email);
    final String DATA_URL = "http://192.168.2.110/xp/ei_pending_received.php?matri_id="+email+"&page=";
    JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(DATA_URL + String.valueOf(requestCount),
            new Response.Listener<JSONArray>() {
                @Override
                public void onResponse(JSONArray response) {
                    Log.e("response",response.toString());
                    if(response.length()==0){
                        requestCount1 = 1;

                    }
                    else {
                        parseData(response);
                        progressBar.setVisibility(View.GONE);
                    }

                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    progressBar.setVisibility(View.GONE);
                    Toast.makeText(getActivity(), "No More Items Available", Toast.LENGTH_SHORT).show();
                }
            });
    return jsonArrayRequest;
}

private void getData() {
    requestQueue.add(getDataFromServer(requestCount1));
    requestCount1++;
}

private void parseData(JSONArray array) {
    for (int i = 0; i < array.length(); i++) {
        //Log.e("array",array.toString().trim());
        SuperHero superHero = new SuperHero();
        JSONObject json = null;
        try {
            json = array.getJSONObject(i);
            superHero.setImageUrl(json.getString(Config_Test.TAG_IMAGE_URL));
            superHero.setMglId(json.getString(Config_Test.TAG_MGLID));
            superHero.setAge(json.getString(Config_Test.TAG_AGE));
            superHero.setAgeHeight(json.getString(Config_Test.TAG_HEIGHT));
            superHero.setCommunity(json.getString(Config_Test.TAG_COMMUNITY));
            superHero.setCaste(json.getString(Config_Test.TAG_CASTE));
            superHero.setOccupation(json.getString(Config_Test.TAG_OCCUPATION));
            superHero.setIncome(json.getString(Config_Test.TAG_INCOME));
            superHero.setStatus(json.getString(Config_Test.TAG_STATUS));
            superHero.setRequested_On(json.getString(Config_Test.TAG_REQUESTED_ON));

        } catch (JSONException e) {
            e.printStackTrace();
        }
        listSuperHeroes.add(superHero);
    }
    adapter.notifyDataSetChanged();
}
private boolean isLastItemDisplaying(RecyclerView recyclerView) {
    if (recyclerView.getAdapter().getItemCount() != 0) {
        int lastVisibleItemPosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findLastCompletelyVisibleItemPosition();
        if (lastVisibleItemPosition != RecyclerView.NO_POSITION && lastVisibleItemPosition == recyclerView.getAdapter().getItemCount() - 1)
            return true;
    }
    return false;
}
void exit(){
    Toast.makeText(getContext(),"no more data avilable",Toast.LENGTH_SHORT).show();
 }
 }

下面是我添加所有选项卡的 Activity 类

private void setupViewPager(ViewPager viewPager) {
    int numberOfPages=7;
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new NewMatches_Tab(), "New matches");
    adapter.addFragment(new Broader_Match_Tab(), "Broader Matches");
    adapter.addFragment(new Similar_Matchs_Tab(), "Similar Matches");
    adapter.addFragment(new ShortlistTab(), "ShortListed");
    adapter.addFragment(new Viewed_My_Profile(), "View My Profile");
    adapter.addFragment(new ShortListedMeTab(), "ShortListed Me");
    adapter.addFragment(new Photo_Request_Received(), "Photo Request Received");
    //viewPager.setOffscreenPageLimit(numberOfPages);
    viewPager.setAdapter(adapter);
  }

Answer 1

您可以在活动中添加一个 OnPageChangeListener 并将其注册到您的视图寻呼机并在 OnPageChangeListener 实例中进行所有必要的“设置”。

ViewPager.OnPageChangeListener viewPagerPageChangeListener = new ViewPager.OnPageChangeListener() {

    @Override
    public void onPageSelected(int position) {
        //Do your fragment refreshing here
        mCurrentPage = position;
    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {

    }

    @Override
    public void onPageScrollStateChanged(int arg0) {

    }
};

@Override
public void setFragmentsForContents(List<Content> contents) { //bundle data for your different fragments
    if(contents!=null){
        NUM_PAGES = contents.size();
        mContentPager.addOnPageChangeListener(viewPagerPageChangeListener);
        mContentPager.setAdapter(mScreenSlidePagerAdapter);
        mContentPager.setCurrentItem(mCurrentPage);
    }
}

private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
    ScreenSlidePagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        return ContentFragment.newInstance(mContents.get(position).getContent());
    }

    @Override
    public int getCount() {
        return NUM_PAGES;
    }

    @NonNull
    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        return super.instantiateItem(container, position);
    }

    @Override
    public float getPageWidth(int position) {
        return 1.0f;
    }

}