Develop Reference

Android: Recyclerview in Bottom Navigation Bar Fragment populated with SQLite will not update

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!

open a Fragment by clicking on a recyclerview item and move to this fragment

i'm trying to open a Fragment by clicking on a recyclerview item, what i'm getting after clicking on item is both fragment toghter, i see the image from the fragment that i want to go to after the clicking on my recyclerview..Does anyone have any idea what i'm doing wrong?
public class MainActivity extends AppCompatActivity {
private FragmentManager manger;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayList<Chat> chatList = new ArrayList<>();
chatList.add(new Chat("send post card", " ", R.drawable.sentpostcard));
chatList.add(new Chat("send greeting card", "happy holiday", R.drawable.greetingcard));
chatList.add(new Chat("special designs", "choose a card", R.drawable.special));
ChatAdapter adapter = new ChatAdapter(chatList);
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.chatList);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(adapter);
}
// 1
public class ChatAdapter extends RecyclerView.Adapter<ChatAdapter.ChatViewHolder>{
// 7
private ArrayList<Chat> chats;
// 8
public ChatAdapter(ArrayList<Chat> chats) {
this.chats = chats;
}
// 10
#Override
public ChatViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = getLayoutInflater();
View v = inflater.inflate(R.layout.chat_list_item, parent, false); // false == do not attach to root
return new ChatViewHolder(v);
}
// 11
#Override
public void onBindViewHolder(ChatViewHolder holder, int position) {
holder.bind( chats.get(position) );
}
// 9
#Override
public int getItemCount() {
return chats.size();
}
// 2
public class ChatViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
//4
private TextView textName, textChat;
private ImageView imageChat;
//we need to remember a chat for each view holder and we bind the chat object using the bind function
//this will be useful later in the onClick Listener
private Chat c;
// view is the layout view ==> it contains all of the view in the layout file
// 3
public ChatViewHolder(View itemView) {
super(itemView);
// 5
textName = (TextView) itemView.findViewById(R.id.textName);
textChat = (TextView) itemView.findViewById(R.id.textChat);
imageChat = (ImageView) itemView.findViewById(R.id.imageChat);
// 12
itemView.setOnClickListener(this);
}
// 6
public void bind(Chat chat){
c = chat;
textName.setText(chat.getName());
textChat.setText(chat.getText());
imageChat.setImageResource(chat.getImage());
}
#Override
public void onClick(View v) {
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,new FragA()).commit();
}
}
}
}

Would be nice to see you layout xml, but from what I can see:
Your recycler view is not inside a fragment - it is inside the MainActivity. You set it with setContentView(R.layout.activity_main);
When you do
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,new FragA()).commit();
you put your new fragment in the fragment_container view group. But this does not affect the activity at all. So, you end up with both views visible.
There are two ways to fix this:
The easy and hacky one - set solid background (i.e android:background="#android:color/black") to your fragment and add android:clickable="true" to it's root layout. Then you won't be able to see or interact with the activity that will be beneath your fragment.
More proper way - put your recycler view in a fragment, put that fragment in the fragment_container with getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, recyclerFragment).commit();. Then it will be replaced with your new fragment on item click when you call getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,new FragA()).commit();
To be able to go back to the recycler view you will also need to call addToBackStack method

ViewPager stucks while swiping views

I have created a viewpager with tabslayout.Each view of viewpager consists of recyclerview inside fragment.The issue i am having is that when i swipe through the views it stucks while swiping in such a manner that there is no change in view and i have to swipe multiple times in order to change view.It looks that swipe event is not detected by viewpager.However if i comment out below two lines which includes setting adapter then i don't experience such issue and swipe is smooth and fast.
PlanListAdapter mAdapter = new PlanListAdapter(browsePlanModelList, getActivity());
rvBrowsePlanList.setAdapter(mAdapter);
Where am i going wrong and how can i resolve this?
Below is code of fragment and adapter-
public class FullTimeFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_browse_plan_list, container, false);
ArrayList<BrowsePlanModel> browsePlanModelList = (ArrayList<BrowsePlanModel>) getArguments().getSerializable(AppConstant.BROWSEPLANlIST);
RecyclerView rvBrowsePlanList = (RecyclerView) view.findViewById(R.id.rvBrowsePlanList);
//rvBrowsePlanList.addItemDecoration(new SimpleDividerIncludingLastItemDecoration(getResources()));
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
rvBrowsePlanList.setLayoutManager(mLayoutManager);
rvBrowsePlanList.setItemAnimator(new DefaultItemAnimator());
if(browsePlanModelList!=null)
{
BrowsePlanListAdapter mAdapter = new BrowsePlanListAdapter(browsePlanModelList, getActivity());
rvBrowsePlanList.setAdapter(mAdapter);
}
return view;
}
}
Adapter
public class PlanListAdapter extends RecyclerView.Adapter<PlanListAdapter.MyViewHolder> {
private List<BrowsePlanModel> planList;
Context mContext;
public PlanListAdapter(List<BrowsePlanModel> planList, Context mContext) {
this.mContext = mContext;
this.planList = planList;
}
#Override
public PlanListAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext())
.inflate(R.layout.sffs_item, parent, false);
return new MyViewHolder(itemView);
}
#Override
public void onBindViewHolder(PlanListAdapter.MyViewHolder holder, int position) {
holder.xyz.setText(planList.get(position).getxyx());
holder.abc.setText(planList.get(position).getabc());
}
#Override
public int getItemCount() {
return planList.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
public TextView xyz, abc;
public MyViewHolder(View itemView) {
super(itemView);
xyz = (TextView) itemView.findViewById(R.id.xyz);
abc = (TextView) itemView.findViewById(R.id.abc);
}
}
}

Use
myViewPager.setOffscreenPageLimit(number of pages in your viewpager minus 1);
If you do not do this, the pages which are not currently visible will be destroyed and will be recreated every time you swipe. This will lead to huge lag if each of those pages is populating a RecyclerView from a database, etc.

It may be happening because of high resolution image. If you use high resolution images then the viewPager will stuck while swiping . Try using low resolution images.

onCreateViewHolder is never called

I am trying to use recyclerView which is inside a fragment.This is fragment is nested inside the viewPager.
public class UniversityDetail extends Fragment {
RecyclerView universityDetailView;
//need to set Adapter
public static UniversityDetail newInstance(){
return new UniversityDetail();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
View view = inflater.inflate(R.layout.fragment_university_lsit,container,false);
universityDetailView = (RecyclerView)view;
setupViews();
return view;
}
private void setupViews(){
//set the adapter
UniversityDetailAdapter detailAdapter = new UniversityDetailAdapter(new ArrayList<UniversityDetails>());
universityDetailView.addItemDecoration(new RecyclerListDecorater(getActivity()));
universityDetailView.setAdapter(detailAdapter);
universityDetailView.setLayoutManager(new LinearLayoutManager(getActivity()));
universityDetailView.setHasFixedSize(false);
}
public RecyclerView getRecyclerView(){
return this.universityDetailView;
}
}
This is the fragment which i want to be inside the viewPager.It returns a recyclerView from onCreateView.
<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/scroll"
android:paddingBottom="8dp"
android:paddingTop="?attr/actionBarSize"
android:scrollbars="vertical">
fragment_university_lsit.xml
recyclerView uses below adapter.
public class UniversityDetailAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private List<UniversityDetails> universityDetails;
private static Map<String,String> admissionRecommendation;
#Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
((DetailHolder)holder).bind(universityDetails.get(position));
}
#Override
public int getItemCount() {
return universityDetails.size();
}
public UniversityDetailAdapter(List<UniversityDetails> details){
this.universityDetails = details;
}
#Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent,int viewType){
Log.d("CreateUniveristyDetail", "onCreateViewHolder: detail called");
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.detail_fragment,parent,false);
return new DetailHolder(itemView);
}
}
DetailHolder is the class extends ReyclerView.ViewHolder and its implementation is irrelevant here.
The adapter list is upated from handler and notifyDataSetChanged()
private void setup(){
mHandler = new Handler(Looper.getMainLooper()){
#Override
public void handleMessage(Message message){
if(message.what == ConnectionHandler.DETAILMSG){
Log.d("detail handle message", "handleMessage: Called");
List<UniversityDetails> details = (List<UniversityDetails>)message.obj;
UniversityDetailAdapter adapter = (UniversityDetailAdapter)universityDetail.getRecyclerView().getAdapter();
adapter.addAll(details);
adapter.notifyDataSetChanged();
Log.d("size", "handleMessage: " + adapter.getItemCount());
}
}
};
}
Fragment is created in activity..
private void setupNavigation(){
ViewPagerAdapter pagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
universityDetail = UniversityDetail.newInstance();
pagerAdapter.addFragment(universityDetail);
mViewPager.setAdapter(pagerAdapter);
//setup the fragment transaction.
headerTab.setViewPager(mViewPager,0);
//no need to add to back stack
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.add(R.id.view_pager,universityDetail);
transaction.commit();
}
Implementation of DetailHolder
public class DetailHolder extends RecyclerView.ViewHolder{
CardView admissionGeneral;
public View root;
public DetailHolder (View itemView){
super(itemView);
root = itemView;
admissionGeneral = (CardView)root.findViewById(R.id.admission_general);
}
public void bind(UniversityDetails detail){
Log.d("detail bind", "bind: binding to recyclerView");
}
}
here the log of adapter.getItemCount(); return 3; thats means something is being added and onCreateViewHolder is supposed to be called but it never is.
The weird thing is i have implemented another recyclerAdapter is the sameProject and its working perfectly fine.

This problem would be easier to answer if you could show how the universityDetail was assigned from whatever class contains the Handler usage.
It's also not clear how message.obj is able to be cast to a List.
I believe you are using a different instance of the Fragment there than the one that you want to update.
So, you know this line is good
List<UniversityDetails> details = (List<UniversityDetails>)message.obj;
because you see 3 in the output when you do this
Log.d("size", "handleMessage: " + adapter.getItemCount());
Now, these lines could likely be the problem.
UniversityDetailAdapter adapter = (UniversityDetailAdapter)universityDetail.getRecyclerView().getAdapter();
adapter.addAll(details);
adapter.notifyDataSetChanged();
Firstly, there is no addAll method to RecyclerView.Adapter. So I'm not sure how that compiled. Anyways...
Try to keep cross-class references to a minimum. Here, we expose only the method to add the details rather than the entire RecyclerView.
Then, for RecyclerViews, you should notify only the data that was inserted rather than all of it using notifyItemRangeInserted
public class UniversityDetailFragment extends Fragment {
private RecyclerView universityDetailView;
private UniversityDetailAdapter detailAdapter;
private List<UniversityDetails> details = new ArrayList<UniversityDetails>();
...
public void setupViews() {
detailAdapter = new UniversityDetailAdapter(details);
// etc...
}
public void addDetails(List<UniversityDetails> details) {
int curSize = detailAdapter.getItemCount();
this.details.addAll(details);
detailAdapter.notifyItemRangeInserted(curSize, details.size());
}
}
And then just use the instance of your Fragment
if(message.what == ConnectionHandler.DETAILMSG){
Log.d("detail handle message", "handleMessage: Called");
List<UniversityDetails> details = (List<UniversityDetails>) message.obj;
universityDetail.addDetails(details);
Another recommendation would be to use the correct generic type for the holder class to avoid unnecessary casts.
public class UniversityDetailAdapter extends RecyclerView.Adapter<DetailHolder>

Can't make Fragment with RecyclerView work

I have to create a list inside one of my Fragments but I cannot make recyclerview work, I was searching the internet whole day followed tutorials but could not figure out why its not working
row_item.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/list"
android:name="com.streak.roadpoliceviolations.ViolationFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
app:layoutManager="LinearLayoutManager"
tools:context="com.streak.roadpoliceviolations.ViolationFragment"
tools:listitem="#layout/fragment_violation" />
Adapter:
public class ViolationAdapter extends RecyclerView.Adapter<ViolationAdapter.MyViewHolder>{
private LayoutInflater inflater;
List<ViolationItem> data= Collections.emptyList();
public ViolationAdapter(List<ViolationItem> data) {
//inflater = LayoutInflater.from(context);
this.data = data;
}
#Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.fragment_violation, parent, false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
ViolationItem current = data.get(position);
holder.txt1.setText(current.txt1);
holder.txt2.setText(current.txt2);
}
#Override
public int getItemCount() {
return 0;
}
class MyViewHolder extends RecyclerView.ViewHolder {
TextView txt1;
TextView txt2;
public MyViewHolder(View itemView) {
super(itemView);
txt1= (TextView) itemView.findViewById(R.id.txt1);
txt2= (TextView) itemView.findViewById(R.id.txt2);
}
}
}
Fragment class
public class ViolationFragment extends Fragment {
private ViolationAdapter adapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_violation_list, container, false);
RecyclerView rv = (RecyclerView) view.findViewById(R.id.list);
adapter = new ViolationAdapter(getActivity(),getData());
rv.setAdapter(adapter);
rv.setLayoutManager(new LinearLayoutManager(getActivity()));
return view;
}
public static List<ViolationItem> getData() {
List<ViolationItem> data = new ArrayList<>();
String[] txts1 = {"AAA","BBB","CCC"};
String[] txts2 = {"111","222","333"};
for(int i=0; i<=txts1.length; i++) {
ViolationItem c = new ViolationItem();
c.txt1=txts1[i];
c.txt2=txts2[i];
data.add(c);
}
return data;
}
private List<ViolationItem> createList() {
List<ViolationItem> data = new ArrayList<>();
return data;
}
}
Everything passes without a single warning BUT I cannot place this into the fragment container
In mine activity I'm calling the fragment with the following code
//Initial fragment
ViolationFragment frag = new ViolationFragment();
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction() .replace(R.id.frame_container, frag).commit();
Getting this error during the build
Error:(77, 75) error: incompatible types: ViolationFragment cannot be converted to Fragment
And if i change frag initialization Fragment frag = new ViolationFragment();
I get the same error.
How to finally fix this and make the fragment work?!

As I remember you must use support library fragment to make it work. Please check and confirm.