So this is the AsyncTask that I run in onCreateView in the first fragment
class GetDatas extends AsyncTask<Void, Void, Void>
{
Collection<ProfileDataModel> enums = Collections.EMPTY_LIST;
#Override
protected Void doInBackground(Void... voids) {
try{
client = new OkHttpClient();
String response = OkHttpService.GET(client, webUrl);
Gson gson = new Gson();
Type type = new TypeToken<Collection<ProfileDataModel>>(){}.getType();
enums = gson.fromJson(response, type);
profileDataModels = enums.toArray(new ProfileDataModel[enums.size()]);
listAdapter = new ListAdapter(Arrays.asList(profileDataModels), getContext());
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
profileDataModels = enums.toArray(new ProfileDataModel[enums.size()]);
listAdapter = new ListAdapter(Arrays.asList(profileDataModels), getContext());
recyclerView.setAdapter(listAdapter);
recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 3));
}
}
On the third fragment I use dummy data that does not require fetching
public class MainFragment extends Fragment {
RecyclerView recyclerView;
LinearLayout linearLayout;
#Override
public View onCreateView(
LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_video_list_pages, container, false);
recyclerView = (RecyclerView) rootView.findViewById(R.id.video_list_recycler_view);
recyclerView.setHasFixedSize(true);
linearLayout = (LinearLayout) rootView.findViewById(R.id.video_list_adapter_rootframe);
ListAdapter adapter = new ListAdapter(
new String[] {
"mm","aa","sss","mm","aa","sss","mm","aa","sss","mm","aa","sss","mm","aa","sss"
}
);
recyclerView.setAdapter(adapter);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(linearLayoutManager);
return rootView;
}
}
Some of you maybe confused by the naming, but I like to keep it that way,
My Directory names
The problem is that when I swipe to the third fragment from the first fragment, the recycle view redraws itself. This doesn't happen when I go to the second fragment, which only contains a textview
Can someone explain why this happens?
ok whats happening is the fragment one is being destroyed when you go to the third fragment so to stop this functionality you have to override destroyItem and keep it blank, use it in your Activity class
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
}
and your problem will be solved and next time try to go through all methods of the class before posting a question.
Suppose you had 4 fragments in the Tabs it will keep only 2 and destroy rest to save memory you, it can also keep 3 if you have next and previous tab like number two if you have 3 tabs, you can override it by keeping destroyItem empty cheers!
Don't try to implement if you have scrolling 10-20 tabs your application might crash
You can do like this in OnCreate() when setting up the adapter
mAdapter.stateRestorationPolicy = RecyclerView.Adapter.StateRestorationPolicy.PREVENT_WHEN_EMPTY
This way, the adapter will save its position in case the fragment gets destroyed and recreated.
Related
I have a BottomNavigationBar with 3 fragments. In the first fragment, I try to put SQLite data into a recyclerview. It works fine except for the fact that I need to switch between the Navigation Bar items in order to see the refreshed recyclerview. When I use a handler with postDelayed however, it does show the refreshed recyclerview if I set around 1 sec of delay. 0.2 secs wont work already.
Even though this is still very generic: is there any best practice for this? It seems to me that I need to use AsyncTask which has been -however- deprecated.
Thanks!
Simon
HomeFragment
public class HomeFragment extends Fragment {
private HomeViewModel homeViewModel;
private Context context;
private CardView cardview;
private LinearLayout.LayoutParams layoutparams;
private TextView textview;
private RelativeLayout relativeLayout;
private myDbAdapter helper;
RecyclerView myView;
public View onCreateView(#NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
homeViewModel =
new ViewModelProvider(this).get(HomeViewModel.class);
View root = inflater.inflate(R.layout.fragment_home, container, false);
helper = new myDbAdapter(getContext());
myView = (RecyclerView) root.findViewById(R.id.recyclerview_home);
RecyclerViewAdapter3 adapter = new RecyclerViewAdapter3(new ArrayList<String>(Arrays.asList(helper.classes())));
myView.setHasFixedSize(true);
myView.setAdapter(adapter);
LinearLayoutManager llm = new LinearLayoutManager(getContext());
llm.setOrientation(LinearLayoutManager.VERTICAL);
myView.setLayoutManager(llm);
homeViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
#Override
public void onChanged(#Nullable String s) {
textView.setText(s);
}
});
return root;
}
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}
public void refresh(View v){
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
public void run() {
myView = (RecyclerView) v.findViewById(R.id.recyclerview_home);
helper = new myDbAdapter(v.getContext());
ArrayList<String> classes = new ArrayList(Arrays.asList(helper.classes()));
ArrayList<String> subClasses = new ArrayList(Arrays.asList(helper.subClasses()));
RecyclerViewAdapter3 adapter = new RecyclerViewAdapter3(classes);
myView.setHasFixedSize(true);
myView.setAdapter(adapter);
LinearLayoutManager llm = new LinearLayoutManager(v.getContext());
llm.setOrientation(LinearLayoutManager.VERTICAL);
myView.setLayoutManager(llm);
}
}, 1000); //time in millis
}
}
RecyclerViewAdapter3
public class RecyclerViewAdapter3 extends RecyclerView.Adapter<RecyclerViewAdapter3.MyViewHolder> {
public ArrayList<String> classArrayList;
public ArrayList<String> subClassArrayList;
myDbAdapter helper;
public RecyclerViewAdapter3(ArrayList<String> classArrayList){
this.classArrayList = classArrayList;
}
#Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View listItem = LayoutInflater.from(parent.getContext()).inflate(R.layout.cardview, parent, false);
return new MyViewHolder(listItem);
}
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.class.setText(classArrayList.get(position));
holder.delete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
helper = new myDbAdapter(v.getContext());
helper.delete(classArrayList.get(position));
HomeFragment homeFragment = new HomeFragment();
homeFragment.refresh(v.getRootView());
}
});
holder.selectButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
}});}
#Override
public int getItemCount() {
return classArrayList.size();
}
public static class MyViewHolder extends RecyclerView.ViewHolder {
private TextView class;
private Button selectButton;
private ImageView delete;
public MyViewHolder(View itemView) {
super(itemView);
class = (TextView)itemView.findViewById(R.id.name);
selectButton = (Button) itemView.findViewById(R.id.selectButton);
delete = (ImageView) itemView.findViewById(R.id.delete);
}
}
}
Thanks for posting your code :)
There are a fair few things that can go wrong in your code as it is right now, and I can't really pinpoint what causes it to work when you use postDelay. I'm going to list a few, which you can look into:
From your onClick() inside your ViewHolder
HomeFragment homeFragment = new HomeFragment();
homeFragment.refresh(v.getRootView());
You should really not instantiate your fragments like this. You can instead pass a callback from your fragment to your adapter (eg.: View.OnClickListener)
You keep re-instantiating your adapter and your helper needlessly. You should create your adapter only once, set it as your recycler view adapter, and save it in a member variable.
Proposed solution
I see that you're already using ViewModel, so you're on a great path for a less error-prone screen, so I suggest that you move your db query-ing logic to your view model. If you're using raw SQLite (instead of Room), you can extend AndroidViewModel, so you'll have access to a context right away. And as you do with your homeViewModel.getText(), you should expose the classes array as live data, observe it, and submit the new list to your adapter.
For submitting your list to your adapter I suggest using ListAdapter, this will provide you a submitList method for submitting the list in the fragment, and inside the adapter, you will have a getItem(int position) method, which you can query inside the onBindViewHolder method.
Inside your fragment, it'll look something like this:
ClassAdapter adapter = null;
View onCreateView(Bundle savedInstanceState) {
super.onCreate(savedInstanceState)
View root = inflater.inflate(R.layout.fragment_home, container, false);
adapter = new ClassAdapter(
new ClassDeleteCallback() {
#Override
void onClassDeleted(Class class) {
// inside view model we can modify db state, than refresh live data
viewModel.deleteClass(class);
}
},
new ClassSelectedCallback() {
// follows same pattern of above
}
);
RecyclerView rv = root.findViewById(R.id.my_rv);
rv.setAdapter(adapter);
rv.setLayoutManager(new LinearLayoutManager(getContext());
homeViewModel.getClasses().observe(getViewLifecycleOwner(), new Observer<List<Class>>() {
#Override
public void onChanged(#Nullable List<Class> classes) {
adapter.submitList(classes);
}
});
homeViewModel.refreshClasses();
return root;
}
I can highly recommend for you to study this project a bit, because it covers lot of the basics which can lead to a much stabler app: Sunflower sample app
I think you should read a bit more about the architecture components, and then go through some code-labs and stuff, and have another go with this screen starting from square one, because it will be easier than fixing the current state :)
I hope this was helpful, and not too discouraging!
I have MainActivity,which contain viewpager,which contain 2 fragments:
MainActivity
ViewPager viewPager = findViewById(R.id.viewPager);
MyPagerAdapter adapter = new MyPagerAdapter(this,
getSupportFragmentManager());
viewPager.setAdapter(adapter);
TabLayout tabLayout = findViewById(R.id.TabLayout);
tabLayout.setupWithViewPager(viewPager);
Fragment fragmentHour=adapter.getItem(1);
onChangeDayListener2= (OnChangeDayListener) fragmentHour;
I am also have interface for send data from main activity in fragment:
public interface OnChangeDayListener{
void OnChange(WeatherList list,int pos);
}
but when i try to work with this callback in interface my recycler adapter always is null:
HourWeatherFragment:
public class HourWeatherFragment extends Fragment implements MainScreen.OnChangeDayListener{
private RecyclerView recyclerView;
private AdapterHour adapter;
private ArrayList<Weather> days;
Context context;
static HttpClient httpClient;
public HourWeatherFragment() {
// Required empty public constructor
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
days=new ArrayList<>();
adapter = new AdapterHour(days,getActivity());
LinearLayoutManager LayoutManager = new LinearLayoutManager(getActivity().getBaseContext(),
LinearLayoutManager.VERTICAL, false);
recyclerView.setLayoutManager(LayoutManager);
recyclerView.setAdapter(adapter);
days.add(new Weather());
recyclerView.getAdapter().notifyDataSetChanged();
Log.d("recycler","adapter seted!");
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_hour_weather, container, false);
recyclerView = rootView.findViewById(R.id.hour_list);
httpClient=new HttpClient();
MyAsyncTask task=new MyAsyncTask();
// task.execute("lviv");
return rootView;
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
this.context=context;
}
#Override
public void OnChange(WeatherList list,int pos) {
String date=list.getAverageWeather().get(pos).getDate();
ArrayList<Weather> weather=list.getByDate(date);
Log.d("ldata","size of weather for adding="+weather.size());
// days.add(new Weather());
if(adapter!=null){
adapter.notifyDataSetChanged();
Log.d("tag","first null!");}
else{
try{
recyclerView.getAdapter();}
catch (NullPointerException ex){
Log.d("tag","null!");//THERE ALWAYS NULL
}}
So,firstly creating activity,then i start load data and when data loaded i send data from MainActivity to HourWeatherFragment throught callback,
but when i receive data in fragment,my adapter is null,how i can fix it?
You can create a static singleton class to hold data and retrieve that data in the fragment.
public class DataHolder {
//create static variables here.
}
In your fragment simply retrieve the data and make it null after that.
Alternative solution
Another solution is to use Bundles. Follow the bundle solution here.
You must cast RecyclerView.
in your fragment and onCreateView method :
recyclerView = (RecyclerView) rootView.findViewById(R.id.hour_list);
I know this is an old question, but contrary to the accepted answer I think the issue is that the handle to the fragment's widget such as recyclerView is not available in the OnCreateView function.
The handles (or pointers if you wish) to the widgets are only guaranteed to exist in the OnViewCreated function.
This documentation has good description of the lifecycle of fragments:
https://guides.codepath.com/android/Creating-and-Using-Fragments
an extract is:
// This event is triggered soon after onCreateView().
// onViewCreated() is only called if the view returned from onCreateView() is non-null.
// Any view setup should occur here. E.g., view lookups and attaching view listeners.
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ListView lv = (ListView) view.findViewById(R.id.lvSome);
lv.setAdapter(adapter);
}
Hope this helps.
I have implemented tabs functionality via SmartTabLayout library in my android application. At present I have used same fragment as viewpager for both of my tabs. Since, the only difference is the view is that sorting of listitems. Below is my HomeActivity code:
HomeActivity.java
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
final ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
final SmartTabLayout viewPagerTab = (SmartTabLayout) findViewById(R.id.viewpagertab);
viewPagerTab.setCustomTabView(this);
FragmentPagerItems pages = new FragmentPagerItems(this);
pages.add(FragmentPagerItem.of("Test1", SampleFragment.class));
pages.add(FragmentPagerItem.of("Test2", SampleFragment.class));
FragmentStatePagerItemAdapter adapter = new FragmentStatePagerItemAdapter(
getSupportFragmentManager(), pages);
viewPager.setAdapter(adapter);
viewPager.setCurrentItem(0);
viewPagerTab.setViewPager(viewPager);
}
#Override
public View createTabView(ViewGroup container, int position, PagerAdapter adapter) {
LayoutInflater inflater = LayoutInflater.from(container.getContext());
View tab = inflater.inflate(R.layout.custom_tab_icon_and_notification_mark, container, false);
TextView txtTab=(TextView)tab.findViewById(R.id.txtTitle);
switch (position){
case 0:txtTab.setText("Test1");break;
case 1:txtTab.setText("Test2");break;
default:throw new IllegalStateException("Invalid pos - "+ position);
}
return tab;
}
My SampleFragment.java is as below wherein I do some server request for data and update the listview adapter.
SampleFragment.java
List<Items> lstItems=new ArrayList<>();
static ItemListAdapter mAdapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view= inflater.inflate(R.layout.fragment_sample, container, false);
ListView lstviewItems = (ListView) view.findViewById(R.id.lstItems);
int position = FragmentPagerItem.getPosition(getArguments());
View emptyView=view.findViewById(R.id.emptyList);
lstviewItems.setEmptyView(emptyView);
mAdapter = new ItemsListAdapter(getActivity(),lstItems);
lstviewItems.setAdapter(mAdapter);
switch (position){
case 0:
//JsonObjectRequest
loadItems();
break;
case 1:
//sort the loaded items
break;
}
return view;
}
private void loadItems(){
try {
JsonArrayRequest request = new JsonArrayRequest(Request.Method.GET,url, null,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
lstItems.clear();
for (int i = 0; i < response.length(); i++) {
//Add item to lstItems
}
mAdapter.notifyDataSetChanged();
}
}
});
testApp.getInstance().addToRequestQueue(request);
} catch (Exception ex) {
ex.printStackTrace();
}
}
But even after mAdapter.notifyDataSetChanged() the listview in the current viewPager tab i.e. Test1 tab is not getting refreshed. Whereas when I navigate to Test2 tab, I can see the changes in the listview, where is data has been loaded properly. Below is the screenshot for 2 different tabs.
I've also searched for this problem and found other solution which did not work for me. One of the solution being, adding a refresh method in ItemsAdapter as below:
public void refresh(List<Items> items)
{
this.items = items;
notifyDataSetChanged();
}
and instead of mAdapter.notifyDataSetChanged() I used mAdapter.refresh(lstItems);. But unfortunately it did not work either. How can I possibly overcome this. Please let me know if I have to add furthermore details on this.
I think your problem is here:
mAdapter = new ItemsListAdapter(getActivity(),lstItems);
You create a new instance of ItemsListAdapter and bind it to the listview with
lstviewItems.setAdapter(mAdapter);
The problem is that this adapter is static. So if you create a new instance you destroy the old adapter and the listview of the other tab has not the adapter anymore that updates your data.
EDIT:
I'd recommend to load the data on a central place. Add the response (your data objects) to a manager class. Then implement on every view which using this data a callback (lets say JsonDataChangedCallback). Register the classes which implementing the callback to the manager with Manager.getInstance().registerCallback(). Then every time your data is changed call updateCallbacks() in your manager and all views will be updated. That's the way implemented that process in my app and it works.
Sample Code:
public class CDMMovieManager {
private CDMMovieManager() {
m_Movies = new ArrayList<>();
m_MovieChangedCallbacks = new ArrayList<>();
}
public static synchronized CDMMovieManager getInstance() {
if(ms_Instance == null)
ms_Instance = new CDMMovieManager();
return ms_Instance;
}
public void addMovie(CDMMovie p_Movie) {
m_Movies.add(p_Movie);
notifyCallbacks();
}
/**
* Registers a movie changed callback
*
* #param p_MovieChangedCallback the callback to register
*/
public void registerMovieChangedCallback(IDMMovieChangedCallback p_MovieChangedCallback) {
m_MovieChangedCallbacks.add(p_MovieChangedCallback);
}
/**
* Removes a movie changed callback
*
* #param p_MovieChangedCallback the callback to remove
*/
public void removeMovieChangedCallback(IDMMovieChangedCallback p_MovieChangedCallback) {
m_MovieChangedCallbacks.remove(p_MovieChangedCallback);
}
private void notifyCallbacks() {
for(IDMMovieChangedCallback l_MovieChangedCallback : m_MovieChangedCallbacks) {
l_MovieChangedCallback.onMoviesChanged();
}
}
}
And the implementing Class:
public class CDMBasicMovieFragment extends Fragment implements IDMMovieChangedCallback {
//...
#Override
public void onMoviesChanged() {
m_Adapter.notifyDataSetChanged();
}
}
I have a ListView that has a SwipeRefreshLayout implemented on it. What I am trying to do is update the ListView when the user swipes down. I've tried looking for different options but unfortunately I am unable to find a solution.
Would it be better to reload the Fragment or the onCreate function?
Here is my code
public class NewsTab extends Fragment implements OnRefreshListener{
final LinkedList<News> listnews = new LinkedList<News>();
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.news_tab, container, false);
swipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.swipe_refresh_layout);
swipeRefreshLayout.setOnRefreshListener(this);
newslist = (ListView) view.findViewById(R.id.displaynews);
populatelist(listnews);
adapter = new CustomAdapter(getActivity(),listnews);
newslist.setAdapter(adapter);
return view;
}
public void onRefresh() {
swipeRefreshLayout.setRefreshing(true);
new StartNewsLoad().execute("");
}
private class StartNewsLoad extends AsyncTask<String, Void, String> {
//ProgressDialog pd = null;
protected String doInBackground(String... params) {
reloadNews();
loadTopNews();
//NewsTab.listnews = new LinkedList<News>();
return null;
}
protected void onPostExecute(String result) {
adapter = new CustomAdapter(getActivity(),listnews);
adapter.notifyDataSetChanged();
swipeRefreshLayout.setRefreshing(false);
}
}
///ANSWER
I found the answer! I added the following line of code inside my costume adapter and called it outside as adapter.refresh();
public void refresh(LinkedList<News> newsList)
{
this.results = newsList;
notifyDataSetChanged();
}
Thank you everybody for your help!
First of all no need to create the adapter again in onPostExecute() as you have already initialized it in onCreateView().You simple need to notify the adapter of the changes in the "listnews" if it has changed.Make sure that your list actually changes before calling the notifyDataSetChanged().
Also please use debugger or log to check whether your onRefresh() is called or not.From the way i see, it should be overriden with #override annotation as it is the method of the interface implemented by your fragment(swipeRefreshLayout.setOnRefreshListener(this);).It should be like:
#Override
public void onRefresh() {
swipeRefreshLayout.setRefreshing(true);
new StartNewsLoad().execute("");
}
In onCreateView() intialize your listview and swiperefereshLayout with listener and set your adapter to your listview like that --->
if(adapter==null&& listNews==null){
listnews=new ArrayList<object>();
adapter=new CustomAdapter(getActivity(),listnews);
listView.setAdapter(adapter);
adapter.notifyDataSetChanged();}
else{
listView.setAdapter(adapter);}
this way it also handle retaining the listData onOrientationchange.
and when you get api response or referesh listview with swipe layout,dont create new adapter just add listNews to your adapter and call adapter.notifyDataSetChanged();
Hy, i've got list view in my fragment. I am replacing this listview fragment with my other fragment but when i want back to my list, it's empty. I thought i could restore my list items but i don't know how. I Assumed that accord with Fragment lifecycle my adapter will be reusable but looks it's not. Here is my code:
public class ThreadListFragment extends Fragment implements FragmentConnectionStatus, ListFragment, OnClickListener, OnItemClickListener{
private ListView ListView;
private PilotController Activity;
private Button ButtonStartNewThread;
private boolean Paused;
private ThreadInfoAdapter adapter;
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
/**
* Inflate the layout for this fragment
*/
super.onCreateView(inflater, container, savedInstanceState);
View view = inflater.inflate(R.layout.threads_list_fragment, container, false);
System.out.println(this.Paused);
if(this.Paused == false){
this.ListView = (ListView) view.findViewById(R.id.listViewActiveThreads);
ArrayList<Guid> strs = new ArrayList<Guid>();
adapter = new ThreadInfoAdapter(view.getContext(), strs, this);
}
this.ListView.setAdapter(adapter);
this.ListView.setItemsCanFocus(true);
this.ListView.setOnItemClickListener(this);
this.Activity = (PilotController) getActivity();
this.ButtonStartNewThread = (Button) view.findViewById(R.id.buttonStartThread);
this.ButtonStartNewThread.setOnClickListener(this);
return view;
}
#Override
public void onPause()
{
super.onPause();
this.Paused = true;
}
but when i return to my old list, it's empty. Could you give me some advice?
SOLUTION
I found a solution. ListView is probably removing from 'draw stack' so when calling OnDeleteView your old list is unusable next time although reference to this object is still set. The solution is to recreate ListView and set old adapter. This adapter due to this tutorial http://developer.android.com/guide/components/fragments.html will survive but view is recreated (so old listview doesn't exist anymore (it exist but it's not drawable). I had to change this lines:
if(this.Paused == false){
this.ListView = (ListView) view.findViewById(R.id.listViewActiveThreads);
ArrayList<Guid> strs = new ArrayList<Guid>();
adapter = new ThreadInfoAdapter(view.getContext(), strs, this);
}
to:
this.ListView = (ListView) view.findViewById(R.id.listViewActiveThreads);
if(this.Paused == false){
ArrayList<Guid> strs = new ArrayList<Guid>();
adapter = new ThreadInfoAdapter(view.getContext(), strs, this);
}
In "onActivityCreated" you can just check if your dataList (in your case "strs) is empty. If it is not then just use it, otherwise create a new one. In code it would look like this:
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (strs == null)
strs = new ArrayList<Guid>();
mListView = (ListView)getActivity().findViewById(R.id.listViewActiveThreads);
mPersonAdapter = new ArrayAdapterPerson(getActivity(),mPersonList,this);
mListView.setAdapter(mPersonAdapter);
}
I found my solution here: ListFragment is empty after going back
use transaction.hide(this):
ft.addToBackStack(null);
ft.hide(this);
ft.add(R.id.frag_frame, lyrics);
ft.commit();