I'm using PositionalDataSource and LiveData/PagedListAdapter
I want to make my recyclerview scroll to specific position when given a corresponding key value.
How to do this?
added my trial code : what i hope is when button clicked recyclerview method scrolltoposition works well.. but I know it's an incorrect way. I believe i need to use key instead of this direct access.
itemViewModel.getAllItems().observe(this, new Observer<List<Item>>() {
#Override
public void onChanged(#Nullable List<Item> itemList) {
itemViewModel.getPagedListLiveData(itemList).observe(MainActivity.this, new Observer<PagedList<Item>>() {
#Override
public void onChanged(#Nullable PagedList<Item> items) {
adapter.submitList(items);
}
});
}
});
binding.button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ItemDataSource dataSource = itemViewModel.getDataSource();
dataSource.invalidate();
binding.rv.getLayoutManager().scrollToPosition(20000);
}
});
datasource class
public class ItemDataSource extends PositionalDataSource<Item> {
private List<Item> list;
public ItemDataSource(List<Item> list) {
this.list = list;
}
private int computeCount() {
return list.size();
}
private List<Item> loadRangeInternal(int startPosition, int loadCount) {
List<Item> modelList = new ArrayList<>();
int endPosition = Math.min(computeCount(), startPosition + loadCount);
for (int i = startPosition; i < endPosition; i++) {
modelList.add(list.get(i));
}
return modelList;
}
#Override
public void loadInitial(#NonNull LoadInitialParams params, #NonNull LoadInitialCallback<Item> callback) {
int totalCount = computeCount();
int position = computeInitialLoadPosition(params, totalCount);
int loadSize = computeInitialLoadSize(params, position, totalCount);
callback.onResult(loadRangeInternal(position, loadSize), position, totalCount);
}
#Override
public void loadRange(#NonNull LoadRangeParams params, #NonNull LoadRangeCallback<Item> callback) {
callback.onResult(loadRangeInternal(params.startPosition, params.loadSize));
}
repository class
public class ItemRepository {
private ItemDao itemDao;
private LiveData<List<Item>> allItems;
private MutableLiveData<PagedList<Item>> pagedListLiveData = new MutableLiveData<>();
private ItemDataSource dataSource;
public ItemRepository(Application application) {
ItemDatabase database = ItemDatabase.getInstance(application.getApplicationContext());
itemDao = database.itemDao();
allItems = itemDao.getAllItems();
}
public LiveData<PagedList<Item>> getPagedListLiveData(List<Item> itemList) {
dataSource = new ItemDataSource(itemList);
PagedList.Config config = new PagedList.Config.Builder()
.setPageSize(200)
.setEnablePlaceholders(false)
.build();
PagedList<Item> itemPagedList = new PagedList.Builder<>(dataSource, config)
.setInitialKey(10000)
.setNotifyExecutor(new MainThreadExecutor())
.setFetchExecutor(Executors.newSingleThreadExecutor())
.build();
pagedListLiveData.setValue(itemPagedList);
return pagedListLiveData;
}
public ItemDataSource getDataSource() {...}
public LiveData<List<Item>> getAllItems() {...}
If you have a recyclerView object then you can use method scrollToPosition(position: Int)
Related
I am using retrofit2 for fetching data from the server and after fetching saving data in room database and then showing in recycler view. But it is no displayed (my data what I get using retrofit). I try display it in my fragment. In file ...data/data/databese/source.db these data are saved. I see it. So, that means that my code works. But I can't understand why it is not displayed.
my database class:
#Database(entities = {Source.class}, exportSchema = false, version = 1)
public abstract class SourceDatabase extends RoomDatabase {
private static final String DB_NAME = "source.db";
public abstract SourceDao sourceDao();
private static SourceDatabase instance;
public static SourceDatabase getInstance(Context context) {
if (instance == null) {
instance =buildDatabaseInstance(context);
}
return instance;
}
private static SourceDatabase buildDatabaseInstance(Context context) {
return Room.databaseBuilder(context,
SourceDatabase.class,
DB_NAME).build();
}
}
repository:
public class DataBaseRepository {
private static DataBaseRepository dataBaseRepository;
private SourceDao sourceDao;
private LiveData<List<Source>> allSourcestoDb;
private Context context;
public static DataBaseRepository getInstance(Context context) {
if (dataBaseRepository == null) {
dataBaseRepository = new DataBaseRepository(context);
}
return dataBaseRepository;
}
public DataBaseRepository(Context context) {
this.context = context;
SourceDatabase db = SourceDatabase.getInstance(context);
sourceDao = db.sourceDao();
allSourcestoDb = sourceDao.getSources();
}
public void getSourceListTodb(String key) {//отправка данных в LiveData
RestClient restClient = RestClient.getInstance();
restClient.startRetrofit();
restClient.getServerApi().getNews(key).enqueue(new Callback<News>() {
#Override
public void onResponse(Call<News> call, Response<News> response) {
Completable.fromAction(new Action (){
#Override
public void run() throws Exception {
if (response.body() != null) {
List<Source> list = response.body().getSources();
sourceDao.insert(list);
}
}
}).subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new CompletableObserver() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onComplete() {
}
#Override
public void onError(Throwable e) {
}
});
}
#Override
public void onFailure(Call<News> call, Throwable t) {
Log.d("error", "Can't parse data " + t);
}
});
}
public LiveData<List<Source>> getAllSourcestoDb() {
return allSourcestoDb;
}
}
dao:
#Dao
public interface SourceDao {
#Insert(onConflict = OnConflictStrategy.REPLACE)
void insert(List<Source> sources);
#Query("SELECT * FROM source")
LiveData<List<Source>> getSources();
}
viewModel:
public class SourceViewModel extends AndroidViewModel {
private DataBaseRepository dataBaseRepository;
private LiveData<List<Source>> allSources; //for db
public SourceViewModel(#NonNull Application application) {
super(application);
dataBaseRepository =DataBaseRepository.getInstance(application); //for db
allSources = dataBaseRepository.getAllSourcestoDb();
}
public LiveData<List<Source>> getAllSources() {
return allSources;
}
}
and fragment:
public class SavedDataFragment extends Fragment {
private SourceViewModel sourceViewModel;
private DataBaseRepository dataBaseRepository;
private RecyclerView recyclerView;
private List<Source> sourceList;
private SavedDataAdapter adapter;
public SavedDataFragment() {
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.saved_data,container,false);
DataSharedPreference sharedPreference = DataSharedPreference.getSPInstance();
String api_key = sharedPreference.loadText(getActivity());
dataBaseRepository = new DataBaseRepository(getActivity());
sourceViewModel = ViewModelProviders.of(this).get(SourceViewModel.class);
recyclerView = view.findViewById(R.id.recyclerViewSavedFragment);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(view.getContext()));
sourceList = new ArrayList<>();
adapter = new SavedDataAdapter(getActivity(), sourceList);
recyclerView.setAdapter(adapter);
sourceViewModel.getAllSources().observe(this, new Observer<List<Source>>() {
#Override
public void onChanged(List<Source> sources) {
adapter.setSourceList(sourceList);
}
});
dataBaseRepository.getSourceListTodb(api_key);
return view;
}
}
adapter:
public class SavedDataAdapter extends RecyclerView.Adapter<SavedDataAdapter.SourceSavedViewHolder> {
private LayoutInflater inflater;
private List<Source> sources;
public SavedDataAdapter(Context context, List<Source> sources) {
this.sources = sources;
this.inflater = LayoutInflater.from(context);
}
#NonNull
#Override
public SavedDataAdapter.SourceSavedViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.saved_item, parent, false);
return new SourceSavedViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull final SavedDataAdapter.SourceSavedViewHolder holder, int position) {
final Source source = sources.get(position);
holder.sourceId.setText(source.getId());
holder.sourceName.setText(source.getName());
holder.sourceDescription.setText(source.getDescription());
holder.sourceURL.setText(source.getUrl());
holder.sourceCategory.setText(source.getCategory());
holder.sourceLanguage.setText(source.getLanguage());
holder.sourceCountry.setText(source.getCountry());
}
#Override
public int getItemCount() {
return sources.size();
}
public void setSourceList(List<Source> sources) {
this.sources = sources;
notifyDataSetChanged();
}
public static class SourceSavedViewHolder extends RecyclerView.ViewHolder {
TextView sourceName, sourceId, sourceDescription, sourceURL, sourceCategory, sourceLanguage, sourceCountry;
public SourceSavedViewHolder(View view) {
super(view);
sourceName = view.findViewById(R.id.sourceName);
sourceId = view.findViewById(R.id.sourceIdItem);
sourceDescription = view.findViewById(R.id.sourceDescription);
sourceURL = view.findViewById(R.id.sourceURL);
sourceCategory = view.findViewById(R.id.sourceCategory);
sourceLanguage = view.findViewById(R.id.sourceLanguage);
sourceCountry = view.findViewById(R.id.sourceCountry);
}
}
}
In your Fragment inside onChanged,
you're setting adapter.setSourceList(sourceList) where sourceList is an empty arrayList.
You should instead setSourceList to sources which is the updated list passed as an argument to onChanged method
That is :-
sourceViewModel.getAllSources().observe(this, new Observer<List<Source>>() {
#Override
public void onChanged(List<Source> sources) {
adapter.setSourceList(sources); // sources and not sourceList
}
});
Also there are few more things that should be taken care of.
For ex- in your observe method, you have passed this as first argument which is wrong when using Fragments as it may causes memory leaks. Instead you should pass viewLifeOwner..
More can found on this link Use viewLifecycleOwner as the LifecycleOwner
Try ti change this:
#Query("SELECT * FROM source")
To:
#Query("SELECT * FROM Source")
I am trying to figure out why the LiveData observer for getAllGoals() does not trigger immediately in the fragment when I update a record. However, the observer is called only after switching to another fragment using the bottom tab navigation and then coming back to the original fragment.
The fragment in question:
MyGoalsFragment.java
public class MyGoalsFragment extends Fragment implements MyGoalsAdapter.MyGoalsCallback {
FragmentMyGoalsBinding myGoalsBinding;
private MyGoalsViewModel myGoalsViewModel;
MyGoalsAdapter myGoalsAdapter;
ConstraintSet smallConstraintSet = new ConstraintSet();
public View onCreateView(#NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
myGoalsViewModel = new ViewModelProvider(getActivity(), ViewModelProvider.AndroidViewModelFactory.getInstance(getActivity().getApplication())).get(MyGoalsViewModel.class);
myGoalsBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_my_goals, container, false);
myGoalsBinding.recyclerView2.setLayoutManager(new LinearLayoutManager(getActivity()));
DrawerLayout drawerLayout = (DrawerLayout) getActivity().findViewById(R.id.drawer_layout);
myGoalsBinding.menu.setOnClickListener(v -> {
drawerLayout.openDrawer(GravityCompat.START);
});
TransitionManager.beginDelayedTransition(myGoalsBinding.recyclerView2);
myGoalsAdapter = new MyGoalsAdapter();
myGoalsAdapter.setCallback(this);
myGoalsAdapter.setContext(getActivity());
myGoalsAdapter.setRecyclerView(myGoalsBinding.recyclerView2);
myGoalsBinding.recyclerView2.setAdapter(myGoalsAdapter);
myGoalsBinding.floatingActionButton.setOnClickListener(v -> {
startActivity(new Intent(getActivity(), CreateGoalActivity.class));
getActivity().finish();
});
enableSwipeToDeleteAndUndo();
myGoalsBinding.recyclerView2.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (dy > 0 && myGoalsBinding.floatingActionButton.getVisibility() == View.VISIBLE) {
myGoalsBinding.floatingActionButton.hide();
} else if (dy < 0 && myGoalsBinding.floatingActionButton.getVisibility() != View.VISIBLE) {
myGoalsBinding.floatingActionButton.show();
}
}
});
myGoalsViewModel.getAllGoals().observe(getViewLifecycleOwner(), new Observer<List<Goal>>() {
#Override
public void onChanged(List<Goal> goals) {
myGoalsAdapter.submitList(goals); // This observer is not called even after updating a record
}
});
return myGoalsBinding.getRoot();
}
#Override
public void editGoalCallback(Goal goal) {
Intent intent = new Intent(getActivity(), CreateGoalActivity.class);
Bundle bundle = new Bundle();
bundle.putSerializable("goal", goal);
intent.putExtras(bundle);
startActivity(intent);
}
#Override
public void goalCheckBoxCallback(Goal goal) {
myGoalsViewModel.updateGoal(goal);
}
private void enableSwipeToDeleteAndUndo() {
SwipeToDeleteCallback swipeToDeleteCallback = new SwipeToDeleteCallback(getActivity()) {
#Override
public void onSwiped(#NonNull RecyclerView.ViewHolder viewHolder, int i) {
if(i==ItemTouchHelper.LEFT) {
Goal tempGoal = myGoalsAdapter.getGoalAt(viewHolder.getAdapterPosition());
myGoalsViewModel.deleteGoal(tempGoal);
Snackbar.make(myGoalsBinding.rootConstraintLayout, "Goal Deleted", Snackbar.LENGTH_LONG)
.setAction("Undo", v -> {
myGoalsViewModel.insertGoal(tempGoal);
})
.setActionTextColor(getActivity().getResources().getColor(R.color.arcticLimeGreen))
.show();
}else if(i==ItemTouchHelper.RIGHT){
Goal tempGoal = myGoalsAdapter.getGoalAt(viewHolder.getAdapterPosition());
if(tempGoal.isCompleted())
tempGoal.setCompleted(false);
else
tempGoal.setCompleted(true);
TransitionManager.beginDelayedTransition(myGoalsBinding.recyclerView2);
myGoalsViewModel.updateGoal(tempGoal); // This is where the update is called
}
}
};
ItemTouchHelper itemTouchhelper = new ItemTouchHelper(swipeToDeleteCallback);
itemTouchhelper.attachToRecyclerView(myGoalsBinding.recyclerView2);
}
}
The MyGoals ViewModel:
public class MyGoalsViewModel extends AndroidViewModel {
private NoteRepository repository;
private LiveData<List<Goal>> allGoals;
public MyGoalsViewModel(#NonNull Application application) {
super(application);
repository = new NoteRepository(application);
allGoals = repository.getAllGoals();
}
public LiveData<List<Goal>> getAllGoals(){
return allGoals;
}
public void deleteGoal(Goal goal){repository.deleteGoal(goal);}
public void insertGoal(Goal goal){repository.insertGoal(goal);}
public void updateGoal(Goal goal){repository.updateGoal(goal);}
}
The Repository:
public class NoteRepository {
private String DB_NAME = "db_task";
Context context;
private GoalDao goalDao;
private LiveData<List<Goal>> allGoals;
private NoteDatabase noteDatabase;
public NoteRepository(Context context) {
noteDatabase = NoteDatabase.getInstance(context);
goalDao = noteDatabase.goalDao();
allGoals = goalDao.getAllGoals();
this.context = context;
}
public void insertGoal(Goal goal){
new InsertGoalAsyncTask(goalDao).execute(goal);
}
public void deleteGoal(Goal goal){
new DeleteGoalAsyncTask(goalDao).execute(goal);
}
public void updateGoal(Goal goal){
new UpdateGoalAsyncTask(goalDao).execute(goal);
}
public void deleteAllGoals(){
new DeleteAllGoalAsyncTask(goalDao).execute();
}
public LiveData<List<Goal>> getAllGoals(){
return allGoals;
}
private static class InsertGoalAsyncTask extends AsyncTask<Goal,Void,Void>{
private GoalDao goalDao;
private InsertGoalAsyncTask(GoalDao goalDao){
this.goalDao = goalDao;
}
#Override
protected Void doInBackground(Goal... goals) {
goalDao.insert(goals[0]);
return null;
}
}
private static class DeleteGoalAsyncTask extends AsyncTask<Goal,Void,Void>{
private GoalDao goalDao;
private DeleteGoalAsyncTask(GoalDao goalDao){
this.goalDao = goalDao;
}
#Override
protected Void doInBackground(Goal... goals) {
goalDao.delete(goals[0]);
return null;
}
}
private static class UpdateGoalAsyncTask extends AsyncTask<Goal,Void,Void>{
private GoalDao goalDao;
private UpdateGoalAsyncTask(GoalDao goalDao){
this.goalDao = goalDao;
}
#Override
protected Void doInBackground(Goal... goals) {
goalDao.update(goals[0]);
return null;
}
}
private static class DeleteAllGoalAsyncTask extends AsyncTask<Void,Void,Void>{
private GoalDao goalDao;
private DeleteAllGoalAsyncTask(GoalDao goalDao){
this.goalDao = goalDao;
}
#Override
protected Void doInBackground(Void... voids) {
goalDao.deleteAllGoals();
return null;
}
}
}
The DAO class:
#Dao
public interface GoalDao {
#Insert
void insert(Goal goal);
#Update
void update(Goal goal);
#Delete
void delete(Goal goal);
#Query("DELETE from goal_table")
void deleteAllGoals();
#Query("Select * from goal_table order by end_date")
LiveData<List<Goal>> getAllGoals();
}
I have this issue in 2 fragments and there are 2 other fragments that do not have this issue with the exact same implementation. Why is the observer not being called as soon as I update a record in MyGoals fragment?
I found the solution, the problem was not in the LiveData code, but in the Recyclerview ListAdapter & DiffUtil Implementation which stopped from triggering LiveData change.
In MyGoalsAdapter I have used DiffUtil & ListAdapter to have smooth animations and increase performance. For it to work properly we need to compare the new list with the old list. The Problem is where the contents of an object were being marked as equal when they were actually different. I solved this by adding a date field in my Model class modifiedAt
and updated the field before that Object was updated. Here is the snippet of code to explain it better.
MyGoalsAdapter:
public class MyGoalsAdapter extends ListAdapter<Goal, MyGoalsAdapter.MyGoalsViewHolder> {
private Context context;
public MyGoalsAdapter() {
super(DIFF_CALLBACK);
}
private static final DiffUtil.ItemCallback<Goal> DIFF_CALLBACK = new DiffUtil.ItemCallback<Goal>() {
#Override
public boolean areItemsTheSame(#NonNull Goal oldItem, #NonNull Goal newItem) {
return oldItem.getId() == newItem.getId();
}
#Override
public boolean areContentsTheSame(#NonNull Goal oldItem, #NonNull Goal newItem) { //Here we check if the objects in the list have changed fields.
boolean id,desc,iscomp,edate,etime,sdate,stime,title, naya, purana, createdAt, modifiedAt;
id = oldItem.getId() == newItem.getId();
desc = oldItem.getDescription().equals(newItem.getDescription());
purana = oldItem.isCompleted();
naya = newItem.isCompleted();
iscomp = purana && naya;
edate = oldItem.getEnd_date().equals(newItem.getEnd_date());
etime = oldItem.getEnd_time().equals(newItem.getEnd_time());
sdate = oldItem.getStart_date().equals(newItem.getStart_date());
stime = oldItem.getStart_time().equals(newItem.getStart_time());
title = oldItem.getTitle().equals(newItem.getTitle());
createdAt = oldItem.getCreatedAt().equals(newItem.getCreatedAt());
modifiedAt = oldItem.getModifiedAt().equals(newItem.getModifiedAt()); //This will return false for the object that is changed
return id &&
desc &&
iscomp &&
edate &&
etime &&
sdate &&
stime &&
title &&
createdAt &&
modifiedAt
;
}
};
}
When I am updating I set the Object modifiedAt field with the current Date and Time.
Goal tempGoal = myGoalsAdapter.getGoalAt(viewHolder.getAdapterPosition()); //Get the object to make change to it
//make change to the object's field
tempGoal.setModifiedAt(Calendar.getInstance().getTime()); //set the modified date with Current date
myGoalsViewModel.updateGoal(tempGoal); //Update the object to the database
Changing the modifiedAt field will tell the Adapter when there is an object that is updated, triggering the animation and showing the updated object in the List, instantly.
I hope this will help someone.
I using the Paging library in my project.
In Activity, an observer observes the data that the Room library return, when the Room's data changes, the UI update.
And when I scroll to the end of the RecyclerView, the Paging library starts to load data into Room.
But the RecyclerView's list refreshes incorrectly and scroll to the previous position.
What's wrong with my code?
Activity(oberser).
PagingItemRepository repository = new PagingItemRepository(FindDatabase.getInstance(PagingListActivity.this).pagingItemDao());
repository.getAllItems().observe(this, new Observer<PagedList<ItemEntity>>() {
#Override
public void onChanged(PagedList<ItemEntity> itemEntities) {
adapter.submitList(itemEntities);
}
});
Adapter
class PagingListAdapter extends PagedListAdapter<ItemEntity, ItemHolder> {
protected PagingListAdapter() {
super(DIFF_CALLBACK);
}
protected PagingListAdapter(#NonNull DiffUtil.ItemCallback<ItemEntity> diffCallback) {
super(diffCallback);
}
#NonNull
#Override
public ItemHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
return new ItemHolder(LayoutInflater.from(PagingListActivity.this).inflate(R.layout.list_item, parent, false));
}
#Override
public void onBindViewHolder(#NonNull ItemHolder holder, int position) {
ItemEntity entity = getItem(position);
if (entity != null) {
String value = entity.getText();
holder.textView.setText(value);
}
}
}
class ItemHolder extends RecyclerView.ViewHolder {
TextView textView;
public ItemHolder(#NonNull View itemView) {
super(itemView);
textView = itemView.findViewById(R.id.text);
}
}
DiffUtil
private static DiffUtil.ItemCallback<ItemEntity> DIFF_CALLBACK =
new DiffUtil.ItemCallback<ItemEntity>() {
// Concert details may have changed if reloaded from the database,
// but ID is fixed.
#Override
public boolean areItemsTheSame(ItemEntity oldEntity, ItemEntity newEntity) {
return oldEntity.getId() == newEntity.getId();
}
#Override
public boolean areContentsTheSame(ItemEntity oldEntity,
ItemEntity newEntity) {
return oldEntity.equals(newEntity);
}
};
PagingItemRepository
public class PagingItemRepository {
private PagingItemDao itemDao;
LivePagedListBuilder<Integer, ItemEntity> builder;
public PagingItemRepository(PagingItemDao itemDao) {
this.itemDao = itemDao;
DataSource.Factory<Integer, ItemEntity> factory = itemDao.getAllItems();
PagedList.Config config = new PagedList.Config.Builder().
setPageSize(60).
setPrefetchDistance(0).
setEnablePlaceholders(true).
setInitialLoadSizeHint(120).
//setMaxSize(200).
build();
builder = new LivePagedListBuilder<>(factory, config);
builder.setBoundaryCallback(new MyBoundaryCallback(itemDao));
}
LiveData<PagedList<ItemEntity>> getAllItems() {
return builder.build();
}
}
MyBoundaryCallback
public static class MyBoundaryCallback extends PagedList.BoundaryCallback<ItemEntity> {
private PagingItemDao itemDao;
public MyBoundaryCallback(PagingItemDao itemDao) {
this.itemDao = itemDao;
}
#Override
public void onZeroItemsLoaded() {
new Thread(new Runnable() {
#Override
public void run() {
final List<ItemEntity> entities = new ArrayList<>();
for (int i = 0; i < 30; i++) {
count++;
ItemEntity entity = new ItemEntity();
entity.setText(count + "");
entities.add(entity);
}
itemDao.addItems(entities);
}
}).start();
}
#Override
public void onItemAtFrontLoaded(#NonNull ItemEntity itemAtFront) {
}
#Override
public void onItemAtEndLoaded(#NonNull ItemEntity itemAtEnd) {
final Long id = itemAtEnd.getId();
new Thread(new Runnable() {
#Override
public void run() {
if (id >= 530) {
return;
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
final List<ItemEntity> entities = new ArrayList<>();
for (int i = 0; i < 50; i++) {
count++;
ItemEntity entity = new ItemEntity();
entity.setText(count + "");
entities.add(entity);
}
itemDao.addItems(entities);
}
}).start();
}
}
PagingItemDao
#Dao
public interface PagingItemDao {
#Query("select * from item")
DataSource.Factory<Integer, ItemEntity> getAllItems();
#Insert
void addItems(List<ItemEntity> entities);
#Query("delete from item")
void delete();
}
Finally, I solved this problem. ItemEntity, which is my Room entity, its id type is Long type(Reference type) before, then I changed the Long to long type(Basic type), then everything is fine.
I have 2 view models observing 2 tables in room each emitting live data, they should update my recycler view when a value changes. My adapter is equipped to handle more than one model and view holder, but I'm not sure how to update the recycler views adapter with new data without overwriting the current data or duplicating any data any ideas?
So my adapter takes a list of Visitable (Visitable pattern)
I have 2 objects that implement this interface, the interface has a type so I can tell what view holder it wants and I update the recycler view using diff utils, it look like this
public class CardAdapter extends RecyclerView.Adapter<BaseViewHolder> {
private final List<Visitable> elements;
private final TypeFactory typeFactory;
private final ItemTouchListener onItemTouchListener;
private final Context context;
private String cardType;
private final String layoutIdentifier;
private static final String TAG = "Adptr-Card";
private String CARD_CLICK_UPDATE = "card_click_update";
private final String[] imageFilePathNames;
private RequestManager glide;
public CardAdapter(List<Visitable> elements, TypeFactory typeFactory, ItemTouchListener onItemTouchListener,
Context context,
String cardType, String layoutIdentifier, RequestManager glide) {
this.glide = glide;
this.elements = elements;
this.typeFactory = typeFactory;
this.onItemTouchListener = onItemTouchListener;
this.context = context;
this.cardType = cardType;
this.layoutIdentifier = layoutIdentifier;
this.imageFilePathNames = context.getResources().getStringArray(R.array.image_set_names);
}
#NonNull
#Override
public BaseViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View contactView = LayoutInflater.from(context).inflate(viewType, parent, false);
return typeFactory.createViewHolder(contactView, viewType, onItemTouchListener, glide, cardType);
}
#Override
public void onBindViewHolder(#NonNull BaseViewHolder holder, int position) {
holder.bind(elements.get(position), position);
}
#Override
public int getItemViewType(int position) {
return elements.get(position).type(typeFactory);
}
public void setCardType(String cardType) {
this.cardType = cardType;
notifyDataSetChanged();
}
#Override
public int getItemCount() {
return elements.size();
}
public List<Visitable> getList() {
return elements;
}
public List<Sentence> getSentencesList() {
ArrayList<Sentence> sentences = new ArrayList<>();
for (Visitable visitable : elements) {
if (visitable.type(typeFactory) == CardViewHolder.LAYOUT) {
sentences.add((Sentence) visitable);
}
}
return sentences;
}
public Visitable getItem(int position) {
if (position > 0 && position < elements.size()) {
return elements.get(position);
}
return elements.get(0);
}
class CalculateDiffUtils extends AsyncTask<Void, Void, DiffResult> {
private final List<Visitable> oldCardList;
private final List<Visitable> newCardList;
CalculateDiffUtils(List<Visitable> oldCardList, List<Visitable> newCardList) {
this.oldCardList = oldCardList;
this.newCardList = newCardList;
}
#Override
protected DiffUtil.DiffResult doInBackground(Void... params) {
return DiffUtil.calculateDiff(new VisitableDiffUtils(oldCardList, newCardList, typeFactory));
}
#Override
protected void onPostExecute(DiffUtil.DiffResult diffResult) {
super.onPostExecute(diffResult);
dispatchUpdates(diffResult, newCardList);
}
}
private void dispatchUpdates(DiffUtil.DiffResult diffResult, List<Visitable> newCardList) {
this.elements.clear();
this.elements.addAll(newCardList);
diffResult.dispatchUpdatesTo(this);
}
public void refreshDiffUtilsList(List<Visitable> sentences) {
new CalculateDiffUtils(elements, sentences).execute();
}
public void removeItem(int position) {
elements.remove(position);
notifyItemRemoved(position);
}
public void addCard(Sentence sentence) {
elements.add(getItemCount(), sentence);
notifyItemInserted(getItemCount());
}
public void addGroup(GroupsWithSentences sentence) {
elements.add(getItemCount(), sentence);
notifyItemInserted(getItemCount());
}
public void updateCardClick(int position) {
notifyItemChanged(position, CARD_CLICK_UPDATE);
}
public void refreshList(List<Visitable> newElements) {
ArrayList<Visitable> elementArrayList = new ArrayList<>(newElements);
elements.clear();
elements.addAll(elementArrayList);
notifyDataSetChanged();
}
}
My 2 view models sit in a fragment, they observe some data from my Room database and are updated when changes happen, but this means I will only ever have the data from one of the view models, I guess I want a way to combine these view models maybe using some kind of mediator live data, here are my 2 view models (I've removed stuff for brevity, they are both initiated using factories)
GROUP VIEW MODEL
public class GroupViewModel extends ViewModel {
private final GroupRepository groupRepository;
private final LiveData<List<GroupsWithSentences>> groups;
public GroupViewModel(#NonNull Application application, String[] cardArgs) {
groupRepository = new GroupRepository(application);
groups = groupRepository.getGroupsByWordDescriptionAndWordType(cardArgs[0],cardArgs[1]);
}
public LiveData<List<GroupsWithSentences>> getGroups() {
return groups;
}
}
SENTENCE VIEW MODEL
public class CardViewModel extends ViewModel {
private final SentenceRepository sentenceRepository;
private final LiveData<List<Sentence>> cards;
private static final String TAG = "view_model";
public CardViewModel(#NonNull Application application , int clicks){
sentenceRepository = new SentenceRepository(application);
search = new MutableLiveData<>();
cardArgs = new MutableLiveData<>();
cards = Transformations.switchMap(search, mySearch -> sentenceRepository.searchLiveCardListByWordTypeAndWordDescriptionAndSearchWord(getCardArgs()[0],getCardArgs()[1],mySearch));
}
public LiveData<List<Sentence>> getLiveCardList(){
return cards;
}
}
CALLING ADAPTER IN MY FRAGMENT
private void setUpCardViewModelObserver(String[] args) {
cardViewModel.getLiveCardList().observe(getViewLifecycleOwner(), sentenceList -> {
if (sentenceList != null) {
ArrayList<Visitable> list = new ArrayList<>(sentenceList);
cardAdapter.refreshDiffUtilsList(list);
checkResults(list.size());
}
});
}
private void setUpGroupViewModelObserver() {
groupViewModel.getGroups().observe(getViewLifecycleOwner(), groupsWithSentencesList -> {
if (groupsWithSentencesList != null) {
ArrayList<Visitable> list = new ArrayList<>(groupsWithSentencesList);
cardAdapter.refreshDiffUtilsList(list);
checkResults(groupsWithSentencesList.size());
}
});
}
Any help is welcome, many thanks.
So the answer was to use Mediator Live data, i set the new mediator live data to respond to changes to my existing live data objects and then mediate those changes so i now only have one stream of data so my card view model now looks like this
public CardViewModel(#NonNull Application application , int clicks, String[] cardArgs){
sentenceRepository = new SentenceRepository(application);
search = new MutableLiveData<>();
cards = Transformations.switchMap(search, mySearch -> sentenceRepository.searchLiveCardListByWordTypeAndWordDescriptionAndSearchWord(cardArgs[0],cardArgs[1],mySearch));
groupRepository = new GroupRepository(application);
groups = groupRepository.getGroupsByWordDescriptionAndWordType(cardArgs[0],cardArgs[1]);
sentencesAndGroups = new MediatorLiveData<>();
sentencesAndGroups.addSource(cards, sentences -> {
sentencesAndGroups.setValue(combineLatest(sentences, groups.getValue()));
});
sentencesAndGroups.addSource(groups, groupsWithSentences -> {
sentencesAndGroups.setValue(combineLatest(cards.getValue(), groupsWithSentences));
});
}
and my new combine latest method looks like this
private List<Visitable> combineLatest(List<Sentence> sentenceList, List<GroupsWithSentences> groupsWithSentences) {
List<Visitable> visitableList = new ArrayList<>();
if (sentenceList != null){
visitableList.addAll(sentenceList);
}
if (groupsWithSentences != null){
visitableList.addAll(groupsWithSentences);
}
return visitableList;
}
am trying to Fetch the movies data from Mysql DB and show it to Recycler view
but when i run the app nothing shows
here is code i am using Retrofite Library
but i can't parse the Data to the Recycler view
i've made Adapter and Model Class normally like the Json
MainActivity.class
public class MainActivity extends AppCompatActivity {
private static final String url="http://192.168.1.109/stu/";
RecyclerView recyclerViewMovies;
List<MovieListsModels> movies;
MoviesAdapter adapter;
TextView Errortxt;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Errortxt = (TextView)findViewById(R.id.txterror);
recyclerViewMovies = (RecyclerView)findViewById(R.id.recyclerview);
recyclerViewMovies.setHasFixedSize(true);
recyclerViewMovies.setLayoutManager(new LinearLayoutManager(this));
movies = new ArrayList<>();
loadDatafromServer();
}
private void loadDatafromServer() {
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(url)
.addConverterFactory(GsonConverterFactory.create())
.build();
Api api = retrofit.create(Api.class);
Call<MovieListsModels> call = api.ShowMoviesData();
call.enqueue(new Callback<MovieListsModels>() {
#Override
public void onResponse(Call<MovieListsModels> call, Response<MovieListsModels> response) {
try {
MovieListsModels movie = response.body();
adapter = new MoviesAdapter(MainActivity.this, (List<MovieListsModels>) movie);
recyclerViewMovies.setAdapter(adapter);
}
catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void onFailure(Call<MovieListsModels> call, Throwable t) {
Errortxt.setText(t.getMessage().toString());
}
});
}
this is the interface of the methods
Api.class Interface
public interface Api {
#GET("config.php")
Call<MovieListsModels> ShowMoviesData();
}
MovieLists.class
public class MovieListsModels {
public MovieListsModels() {
}
int id;
String movie_name;
String movie_image;
String movie_genre;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getMovie_name() {
return movie_name;
}
public void setMovie_name(String movie_name) {
this.movie_name = movie_name;
}
public String getMovie_image() {
return movie_image;
}
public void setMovie_image(String movie_image) {
this.movie_image = movie_image;
}
public String getMovie_genre() {
return movie_genre;
}
public void setMovie_genre(String movie_genre) {
this.movie_genre = movie_genre;
}
public MovieListsModels(int id, String movie_name, String movie_image, String movie_genre) {
this.id = id;
this.movie_name = movie_name;
this.movie_image = movie_image;
this.movie_genre = movie_genre;
}
}
MovieAdapter.class
public class MoviesAdapter extends RecyclerView.Adapter<MoviesAdapter.MovieHolderView> {
private Context mContext;
private List<MovieListsModels> MovieList = new ArrayList<>();
public MoviesAdapter(Context mContext, List<MovieListsModels> movieList) {
this.mContext = mContext;
MovieList = movieList;
}
#NonNull
#Override
public MovieHolderView onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_item,parent,false);
MovieHolderView holder = new MovieHolderView(view);
return holder;
}
#Override
public void onBindViewHolder(#NonNull MovieHolderView holder, int position) {
MovieListsModels list = MovieList.get(position);
holder.txtName.setText(list.getMovie_name());
holder.txtGenre.setText(list.getMovie_genre());
Picasso.get()
.load(list.getMovie_image())
.into(holder.imgMovie);
}
#Override
public int getItemCount() {
return MovieList.size();
}
public class MovieHolderView extends RecyclerView.ViewHolder {
TextView txtName,txtGenre;
ImageView imgMovie;
public MovieHolderView(View itemView) {
super(itemView);
txtName =(TextView)itemView.findViewById(R.id.movieName);
txtGenre =(TextView)itemView.findViewById(R.id.movieGenre);
imgMovie =(ImageView)itemView.findViewById(R.id.movieImg);
}
}
}
If you receive a list of movies is better because you expect a list, I suppose
public void onResponse(Call<MovieListsModels> call, Response<MovieListsModels> response) {
try {
List<MovieListsModels> movie = response.body();
adapter = new MoviesAdapter(MainActivity.this, movies);
And I believe that not executing the notifyDataSetChanged, you can added like that:
private Context mContext;
private List<MovieListsModels> MovieList = new ArrayList<>();
public MoviesAdapter(Context mContext, List<MovieListsModels> movieList) {
this.mContext = mContext;
MovieList = movieList;
notifiyDataSetChanged();
If you are having json response of the form {..}, you are having an object response and you should expect an object as you have done i.e, Call<YourObject>
If you are having json response of the form [..], you are having an array response and you should expect an array i.e, Call<List<YourObject>>
In your case, i hope its an array(second case), So make changes as per the above answer done by #Guillodacosta
First don't forget to add the internet permission in your manifest file
<uses-permission android:name="android.permission.INTERNET" />
Second try this
Picasso.with(mContext).load(list.getMovie_image()).into(holder.imgMovie);