我有4个片段，每个片段都有recyclerview。 片段将附加到选项卡。当我从一个片段移动到另一个片段并返回到上一个片段时，它没有显示任何数据。
这是我的两个片段文件。
recentFragment.java
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
// return inflater.inflate(R.layout.fragment_recent, container, false);
listItems = new ArrayList<>();
loadRecyclerViewData();
// Inflate the layout for this fragment
v = inflater.inflate(R.layout.fragment_recent, container, false);
rvRecent = (RecyclerView) v.findViewById(R.id.rvRecent);
progressBar =(ProgressBar) v.findViewById(R.id.porgress);
rvRecent.setHasFixedSize(true);
JobAdapter jobAdapter = new JobAdapter(listItems,getContext());
manager = new LinearLayoutManager(getActivity());
rvRecent.setLayoutManager(manager);
rvRecent.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if(newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL){
isScrolling = true;
}
}
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
currentItems = manager.getChildCount();
totalItems = manager.getItemCount();
scrollOutItems = manager.findFirstVisibleItemPosition();
if(isScrolling && (currentItems + scrollOutItems == totalItems)){
//fetch data
isScrolling = false;
loadMoreData();
}
}
});
return v;
}
//test
private void loadRecyclerViewData() {
final ProgressDialog progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("Loading data...");
progressDialog.show();
StringRequest stringRequest = new StringRequest(Request.Method.GET
, URL_DATA, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
progressDialog.dismiss();
try {
JSONObject jsonObject = new JSONObject(response);
JSONArray jsonArray = jsonObject.getJSONArray("employees");
if(jsonArray.length()<counter_2){
counter_2 = jsonArray.length();
//set flag for data completion
}
for(int i = counter_1; i<counter_2; i++){
JSONObject obj = jsonArray.getJSONObject(i);
ListItem item = new ListItem(
obj.getString("name"),
obj.getString("firstappearance"),
obj.getString("imageurl")
);
listItems.add(item);
counter_1 = counter_1 + 1;
}
adapter = new JobAdapter(listItems,getContext()); //check
rvRecent.setAdapter(adapter);
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(stringRequest);
}
private void loadMoreData() {
progressBar.setVisibility(View.VISIBLE);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
StringRequest stringRequest = new StringRequest(Request.Method.GET
, URL_DATA, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
JSONObject jsonObject = new JSONObject(response);
JSONArray jsonArray = jsonObject.getJSONArray("employees");
if(jsonArray.length()>counter_2 * 2){
counter_2 = counter_2 * 2;
}else{
counter_2 = jsonArray.length();
//set flag for data completion
}
for(int i = counter_1; i<counter_2; i++){
JSONObject obj = jsonArray.getJSONObject(i);
ListItem item = new ListItem(
obj.getString("name"),
obj.getString("firstappearance"),
obj.getString("imageurl")
);
listItems.add(item);
counter_1 = counter_1 + 1;
}
// adapter = new JobAdapter(listItems,getApplicationContext());
// rvJob.setAdapter(adapter);
adapter.notifyDataSetChanged();
progressBar.setVisibility(View.GONE);
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(stringRequest);
}
},2000);
}
NotificationsFragment.java
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
listItems = new ArrayList<>();
loadRecyclerViewData();
// Inflate the layout for this fragment
v = inflater.inflate(R.layout.fragment_notifications, container, false);
rvNotifications = (RecyclerView) v.findViewById(R.id.rvNotifications);
progressBar =(ProgressBar) v.findViewById(R.id.porgress);
rvNotifications.setHasFixedSize(true);
JobAdapter jobAdapter = new JobAdapter(listItems,getContext());
manager = new LinearLayoutManager(getActivity());
rvNotifications.setLayoutManager(manager);
rvNotifications.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if(newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL){
isScrolling = true;
}
}
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
currentItems = manager.getChildCount();
totalItems = manager.getItemCount();
scrollOutItems = manager.findFirstVisibleItemPosition();
if(isScrolling && (currentItems + scrollOutItems == totalItems)){
//fetch data
isScrolling = false;
loadMoreData();
}
}
});
return v;
}
private void loadRecyclerViewData() {
final ProgressDialog progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("Loading data...");
progressDialog.show();
StringRequest stringRequest = new StringRequest(Request.Method.GET
, URL_DATA, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
progressDialog.dismiss();
try {
JSONObject jsonObject = new JSONObject(response);
JSONArray jsonArray = jsonObject.getJSONArray("employees");
if(jsonArray.length()<counter_2){
counter_2 = jsonArray.length();
//set flag for data completion
}
for(int i = counter_1; i<counter_2; i++){
JSONObject obj = jsonArray.getJSONObject(i);
ListItem item = new ListItem(
obj.getString("name"),
obj.getString("firstappearance"),
obj.getString("imageurl")
);
listItems.add(item);
counter_1 = counter_1 + 1;
}
adapter = new JobAdapter(listItems,getContext()); //check
rvNotifications.setAdapter(adapter);
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(stringRequest);
}
private void loadMoreData() {
progressBar.setVisibility(View.VISIBLE);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
StringRequest stringRequest = new StringRequest(Request.Method.GET
, URL_DATA, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
JSONObject jsonObject = new JSONObject(response);
JSONArray jsonArray = jsonObject.getJSONArray("employees");
if(jsonArray.length()>counter_2 * 2){
counter_2 = counter_2 * 2;
}else{
counter_2 = jsonArray.length();
//set flag for data completion
}
for(int i = counter_1; i<counter_2; i++){
JSONObject obj = jsonArray.getJSONObject(i);
ListItem item = new ListItem(
obj.getString("name"),
obj.getString("firstappearance"),
obj.getString("imageurl")
);
listItems.add(item);
counter_1 = counter_1 + 1;
}
JobAdapter（listItems，getApplicationContext（））;
adapter.notifyDataSetChanged();
progressBar.setVisibility(View.GONE);
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(stringRequest);
}
},2000);
}
Main2Activity.java
public class Main2Activity extends AppCompatActivity {
private TabLayout tabLayout;
private ViewPager viewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
tabLayout = findViewById(R.id.tabLayout_id);
viewPager = findViewById(R.id.viewPager_id);
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
//adding fragments
adapter.AddFragment(new RecentFragment(),"Recent");
adapter.AddFragment(new JobsFragment(),"Jobs");
adapter.AddFragment(new NotificationsFragment(),"Notifications");
adapter.AddFragment(new RecentFragment(),"Results");
//adapter setup
viewPager.setAdapter(adapter);
tabLayout.setupWithViewPager(viewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.ic_recent_24dp);
tabLayout.getTabAt(1).setIcon(R.drawable.ic_jobs_24dp);
tabLayout.getTabAt(2).setIcon(R.drawable.ic_notifications_black_24dp);
tabLayout.getTabAt(3).setIcon(R.drawable.ic_results_24dp);
}
}
答案 0 :(得分：1)
添加
viewPager.setOffscreenPageLimit(3)
之后
viewPager = findViewById(R.id.viewPager_id);