Deleting In Room Database

Deleting In Room Database - java

I am learning Room DataBase!!
I Know How to Insert and Retrieve Data from Room DataBase to Recycler View!! But In Delete Operation I am getting error of "No Adapter attached Skipped Layout!"
What I want when anyone click on delete button on recycler view . The Task should be deleted
That's why I also Used delete method in Interface and add Interface in Recycler View Adapter which give call back to MainActivity so that we delete and update the recycler view
All of my codes are given below
Here is my Entity Class named as Task
#Entity
public class Task implements Serializable {
#PrimaryKey(autoGenerate = true)
private int id;
#ColumnInfo(name = "task_name")
private String task_name;
#ColumnInfo
private String task_desc;
#ColumnInfo
private String comment;
#ColumnInfo
private String task_comp_date;
#ColumnInfo
private String activate;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTask_name() {
return task_name;
}
public void setTask_name(String task_name) {
this.task_name = task_name;
}
public String getTask_desc() {
return task_desc;
}
public void setTask_desc(String task_desc) {
this.task_desc = task_desc;
}
public String getTask_comp_date() {
return task_comp_date;
}
public void setTask_comp_date(String task_comp_date) {
this.task_comp_date = task_comp_date;
}
public String getComment() {
return comment;
}
public void setComment(String comment) {
this.comment = comment;
}
public String getActivate() {
return activate;
}
public void setActivate(String activate) {
this.activate = activate;
}
}
My Data Accession Object named as TaskDao
#Dao
public interface TaskDao {
#Query("SELECT * FROM task")
List<Task> getAll();
#Insert
void insert(Task task);
#Delete
void delete(Task task);
#Update
void update(Task task);
}
My DataBase
#Database(entities = {Task.class},version = 1)
public abstract class AppDataBase extends RoomDatabase {
public abstract TaskDao taskDao();
}
My DataBaseClient named as DatabaseClient
public class DatabaseClient {
private Context context;
private static DatabaseClient mInstace;
private AppDataBase appDataBase;
public DatabaseClient(Context context) {
this.context = context;
appDataBase = Room.databaseBuilder(context,AppDataBase.class,"MyDailyTask").build();
}
public static synchronized DatabaseClient getInstance(Context context)
{
if(mInstace == null)
{
mInstace = new DatabaseClient(context);
}
return mInstace;
}
public AppDataBase getAppDataBase()
{
return appDataBase;
}
}
My RecyclerView Adapter
public class TaskAdapter extends RecyclerView.Adapter<TaskAdapter.MyViewHolder> {
private Context context;
private List<Task> taskList;
public interface OnDeleteClickListener
{
void OnDeleteClickListener(Task task);
}
private OnDeleteClickListener onDeleteClickListener;
public TaskAdapter(Context context, List<Task> taskList) {
this.context = context;
this.taskList = taskList;
}
public void setOnDeleteClickListener(OnDeleteClickListener onDeleteClickListener) {
this.onDeleteClickListener = onDeleteClickListener;
}
#NonNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view;
view = LayoutInflater.from(context).inflate(R.layout.view_task_list,parent,false);
MyViewHolder myViewHolder = new MyViewHolder(view);
return myViewHolder;
}
#Override
public void onBindViewHolder(#NonNull MyViewHolder holder, int position) {
holder.setData(taskList.get(position).getTask_name(),taskList.get(position).getTask_desc(),taskList.get(position).getComment(),taskList.get(position).getTask_comp_date(),position);
}
#Override
public int getItemCount() {
return taskList.size();
}
class MyViewHolder extends RecyclerView.ViewHolder {
private TextView t1,t2,t3,t4,t5;
private ImageView view;
public MyViewHolder(#NonNull View itemView) {
super(itemView);
t1= itemView.findViewById(R.id.tvCommnt);
t2=itemView.findViewById(R.id.tvDesc);
t3=itemView.findViewById(R.id.tvName);
t4= itemView.findViewById(R.id.tvStart);
t5 = itemView.findViewById(R.id.tvEnd);
view =itemView.findViewById(R.id.tvdele);
}
public void setData(String t01, String t02, String t03, String t05, final int position)
{
t1.setText("Task Comment "+t03);
t2.setText("Task Description "+t02);
t3.setText("Task Name "+ t01);
t4.setText("Start ");
t5.setText("Ënd "+t05);
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(onDeleteClickListener!=null)
{
onDeleteClickListener.OnDeleteClickListener(taskList.get(position));
taskList.remove(position);
notifyDataSetChanged();
}
}
});
}
}
}
MainActivity.java :
public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerView;
ImageView imageView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = findViewById(R.id.ivAdd);
recyclerView = findViewById(R.id.rvTask);
imageView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(getApplicationContext(), AddTaskActivity.class));
}
});
new newTask().execute();
}
class newTask extends AsyncTask<Void,Void, List<Task>> implements TaskAdapter.OnDeleteClickListener {
List<Task> tasks;
#Override
protected List<Task> doInBackground(Void... voids) {
tasks = DatabaseClient.getInstance(getApplicationContext()).getAppDataBase().taskDao().getAll();
return tasks;
}
#Override
protected void onPostExecute(List<Task> tasks) {
super.onPostExecute(tasks);
TaskAdapter taskAdapter = new TaskAdapter(MainActivity.this,tasks);
LinearLayoutManager layoutManager = new LinearLayoutManager(MainActivity.this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.addItemDecoration(new DividerItemDecoration(getApplicationContext(),DividerItemDecoration.VERTICAL));
recyclerView.setAdapter(taskAdapter);
taskAdapter.setOnDeleteClickListener(this);
}
#Override
public void OnDeleteClickListener(final Task task) {
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
DatabaseClient.getInstance(getApplicationContext()).getAppDataBase().taskDao().delete(task);
}
},1000);
}
}

welcome in stack
you interface is declared but not assign so your will throw null pointer when click on item inside your list, but good work your check null before fire method interface
first add setter for OnDeleteClickListener inside your adapter
public void setOnDeleteClickListener(OnDeleteClickListener listener){
this.onDeleteClickListener=listener;
}
and also add code that remove item from you list when user click item
so inside setData method update this code
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (onDeleteClickListener != null) {
onDeleteClickListener.OnDeleteClickListener(taskList.get(position));
//remove item from list and then notify adapter data is changed
taskList.remove(position);
notifyDataSetChanged();
}
}
});
finally to Triggers onDeleteClickListener inside your AsyncTask
update your code here
#Override
protected void onPostExecute(List < Task > tasks) {
super.onPostExecute(tasks);
TaskAdapter taskAdapter = new TaskAdapter(MainActivity.this, tasks, this);
LinearLayoutManager layoutManager = new LinearLayoutManager(MainActivity.this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.addItemDecoration(new DividerItemDecoration(getApplicationContext(), DividerItemDecoration.VERTICAL));
recyclerView.setAdapter(taskAdapter);
//pass this that refer to my interface
taskAdapter.setOnDeleteClickListener(this);
}
inside your OnDelete just use this code to run in another thread
AsyncTask.execute(new Runnable() {
#Override
public void run() {
DatabaseClient.getInstance(getApplicationContext()).getAppDataBase().taskDao().delete(task);
}
});
Advice : Don't name your variable or arguments like String
t01,String t02..etc ,choice name for like what this variable jop
like String taskComment,String taskName ..etc
i hope this help you

Related

Nested RecycleView with Firebase this error "Expected a List while deserializing, but got a class java.util.HashMap" when I insert data using push()

This is the code for the nested recycler view.
If I add data using the push() method, i get the Nested RecycleView with Firebase this error:
Expected a List while deserializing, but got a class java.util.HashMap
AlertDialog dialog;
IFirebaseLoadListener iFirebaseLoadListener;
RecyclerView my_recycler_view;
DatabaseReference myData;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myData= FirebaseDatabase.getInstance().getReference("MyData");
dialog= new SpotsDialog.Builder().setContext(this).build();
iFirebaseLoadListener = this;
// view
my_recycler_view= (RecyclerView)findViewById(R.id.my_recycler_view);
my_recycler_view.setHasFixedSize(true);
my_recycler_view.setLayoutManager(new LinearLayoutManager(this));
load data
getFirebaseData();
}
private void getFirebaseData() {
dialog.show();
myData.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
List<itemGroup> itemGroups= new ArrayList<>();
for(DataSnapshot groupSnapshot: dataSnapshot.getChildren())
{
itemGroup itemGroup= new itemGroup();
///
Firebase instance code
///
itemGroup.setHeaderTitle(groupSnapshot.child("headerTitle").getValue(true).toString());
GenericTypeIndicator<ArrayList<itemData>> genericTypeIndicator= new GenericTypeIndicator<ArrayList<itemData>>(){} ;
itemGroup.setListItem(groupSnapshot.child("listItem").child(key).getValue(genericTypeIndicator));
itemGroups.add(itemGroup);
}
iFirebaseLoadListener.onFirebaseLoadSuccess(itemGroups);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
iFirebaseLoadListener.onFirebaseLoadFailed(databaseError.getMessage());
}
});
}
#Override
public void onFirebaseLoadSuccess(List<itemGroup> itemGroupList) {
MyItemGroupAdapter adapter = new MyItemGroupAdapter(this,itemGroupList);
my_recycler_view.setAdapter(adapter);
dialog.dismiss();
}
#Override
public void onFirebaseLoadFailed(String message) {
Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
dialog.dismiss();
}
}
public class itemData {
private String name ,image;
public itemData() {
}
public itemData(String name, String image) {
this.name = name;
this.image = image;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}
}
public class itemGroup {
private String headerTitle;
private ArrayList<itemData> listItem;
public itemGroup() {
}
public itemGroup(String headerTitle, ArrayList<itemData> listItem) {
this.headerTitle = headerTitle;
this.listItem = listItem;
}
public String getHeaderTitle() {
return headerTitle;
}
public void setHeaderTitle(String headerTitle) {
this.headerTitle = headerTitle;
}
public ArrayList<itemData> getListItem() {
return listItem;
}
public void setListItem(ArrayList<itemData> listItem) {
this.listItem = listItem;
}
}
public class MyItemAdapter extends RecyclerView.Adapter<MyItemAdapter.MyViewHolder> {
private Context context;
private List<itemData> itemDataList;
public MyItemAdapter(Context context, List<itemData> itemDataList) {
this.context = context;
this.itemDataList = itemDataList;
}
#NonNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int i) {
View itemView =
LayoutInflater.from(context).inflate(R.layout.layout_item,viewGroup,false);
return new MyViewHolder(itemView);
}
#Override
public void onBindViewHolder(#NonNull MyViewHolder myViewHolder, int i) {
myViewHolder.txt_item_titles.setText(itemDataList.get(i).getName());
Picasso.get().load(itemDataList.get(i).getImage()).into(myViewHolder.img_item);
myViewHolder.setiItemClickListener(new IItemClickListener() {
#Override
public void onItemClickListener(View view, int i) {
Toast.makeText(context, ""+ itemDataList.get(i).getName(),
Toast.LENGTH_SHORT).show();
}
});
}
#Override
public int getItemCount() {
return (itemDataList != null ? itemDataList.size() : 0);
}
public class MyViewHolder extends RecyclerView.ViewHolder implements
View.OnClickListener {
TextView txt_item_titles;
ImageView img_item;
IItemClickListener iItemClickListener;
public void setiItemClickListener(IItemClickListener iItemClickListener) {
this.iItemClickListener = iItemClickListener;
}
public MyViewHolder (View itemView ){
super(itemView);
txt_item_titles= (TextView)itemView.findViewById(R.id.tvTitle);
img_item= (ImageView) itemView.findViewById(R.id.itemImage);
itemView.setOnClickListener(this);
}
#Override
public void onClick(View v) {
iItemClickListener.onItemClickListener(v,getAdapterPosition());
}
}
}
public class MyItemGroupAdapter extends
RecyclerView.Adapter<MyItemGroupAdapter.MyViewHolder> {
private Context context;
private List<itemGroup> dataList;
public MyItemGroupAdapter(Context context, List<itemGroup> dataList) {
this.context = context;
this.dataList = dataList;
}
#NonNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int i) {
View itemView =
LayoutInflater.from(context).inflate(R.layout.layout_group,viewGroup,false);
return new MyViewHolder(itemView);
}
#Override
public void onBindViewHolder(#NonNull final MyViewHolder myViewHolder, int i) {
myViewHolder.item_title.setText(dataList.get(i).getHeaderTitle());
List<itemData> itemData = dataList.get(i).getListItem();
MyItemAdapter itemListAdapter=new MyItemAdapter(context,itemData);
myViewHolder.recycler_view_item_list.setHasFixedSize(true);
myViewHolder.recycler_view_item_list.setLayoutManager(new
LinearLayoutManager(context,LinearLayoutManager.HORIZONTAL,false));
myViewHolder.recycler_view_item_list.setAdapter(itemListAdapter);
myViewHolder.recycler_view_item_list.setNestedScrollingEnabled(false);
// btn more
myViewHolder.btn_more.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(context, "Button More "+ myViewHolder.item_title.getText(),
Toast.LENGTH_SHORT).show();
}
});
}
#Override
public int getItemCount() {
return (dataList != null ? dataList.size() : 0);
}
public class MyViewHolder extends RecyclerView.ViewHolder{
TextView item_title ;
RecyclerView recycler_view_item_list;
Button btn_more;
public MyViewHolder (View itemView ){
super (itemView);
item_title= (TextView) itemView.findViewById(R.id.itemTitle);
btn_more= (Button)itemView.findViewById(R.id.btMore);
recycler_view_item_list=
(RecyclerView)itemView.findViewById(R.id.recycler_view_list);
}
}
}

This happens when you try to have a structure like this in the database:
"list": {
"-Nasdueqriyew": "First value",
"-Nberqiy39esd": "Second value",
"-Nc3hadsiuhad": "Third value"
}
And then try to map it to a List or array in your Java class.
The JSON structure is not a list, because it was pairs of keys and values, which in Java translates to:
Map<String, Object>
So most likely, the List<itemData> in your code needs to be a Map<String, itemData>.

Androidx RecycleView Not showing items with parse server

This is my adapter for recycle view
CategoryAdapter Class
public class CategoryRAdapter extends RecyclerView.Adapter<CategoryRAdapter.MyViewHolder> {
private Context mcontext;
private List<Food> mData;
RequestOptions option;
public CategoryRAdapter(Context mcontext, List<Food> mData) {
this.mcontext = mcontext;
this.mData = mData;
option = new RequestOptions().centerCrop().placeholder(R.drawable.loading_shape).error(R.drawable.loading_shape);
}
#Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.food_row, parent, false);
return new MyViewHolder(view);
}
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
Food current = mData.get(position);
holder.tv_Name.setText(current.getName());
holder.tv_Rating.setText(current.getRating());
holder.tv_Descip.setText(current.getDescrip());
holder.tv_Category.setText(current.getCateg());
Glide.with(mcontext).load(mData.get(position).getImages()).apply(option).into(holder.img_Thumbnail);
}
#Override
public int getItemCount() {
return mData.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv_Name;
TextView tv_Rating;
TextView tv_Descip;
TextView tv_Category;
ImageView img_Thumbnail;
public MyViewHolder(View itemView) {
super(itemView);
tv_Name = itemView.findViewById(R.id.food_name);
tv_Rating = itemView.findViewById(R.id.rating);
tv_Descip = itemView.findViewById(R.id.desc);
tv_Category = itemView.findViewById(R.id.category);
img_Thumbnail = itemView.findViewById(R.id.thumbnail);
}
}
}
This is my model
Food Class
public class Food {
String Name;
String Images;
String Descrip;
String Rating;
String Categ;
public Food() {
}
public Food(String name, String images, String descrip, String rating, String categ) {
this.Name = name;
this.Images = images;
this.Descrip = descrip;
this.Rating = rating;
this.Categ = categ;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public String getImages() {
return Images;
}
public void setImages(String images) {
Images = images;
}
public String getDescrip() {
return Descrip;
}
public void setDescrip(String descrip) {
Descrip = descrip;
}
public String getRating() {
return Rating;
}
public void setRating(String rating) {
Rating = rating;
}
public String getCateg() {
return Categ;
}
public void setCateg(String categ) {
Categ = categ;
}
}
My mian activity
CategoryActivity Class
public class CategoriaActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private List<Food> dbObjects;
private RecyclerView.Adapter adapter;
private AlertDialog.Builder dialogBuilder;
private AlertDialog dialog;
TextView l_nombre,l_precio;
Button l_finalizar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_categoria);
recyclerView = findViewById(R.id.recycle_id);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
dbObjects = new ArrayList<>();
ParseQuery<ParseObject> query = ParseQuery.getQuery("Category");
query.findInBackground(new FindCallback<ParseObject>() {
public void done(List<ParseObject> objList, ParseException e) {
if (e == null) {
for (ParseObject obj : objList) {
Food food = new Food();
food.setName(obj.getString("Name"));
food.setDescrip(obj.getString("Descrip"));
food.setRating(obj.getString("Rating"));
food.setCateg(obj.getString("Categ"));
food.setImages(obj.getString("Images"));
dbObjects.add(food);
}
} else {
FancyToast.makeText(CategoriaActivity.this, "Error: " + e.getMessage(), FancyToast.LENGTH_SHORT, FancyToast.ERROR, true).show();
}
}
});
adapter = new CategoryRAdapter(this, dbObjects);
recyclerView.setAdapter(adapter);
FloatingActionButton fab = findViewById(R.id.shoppingFlot);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
carritopop();
}
});
}
private void carritopop() {
dialogBuilder = new AlertDialog.Builder(this);
View view = getLayoutInflater().inflate(R.layout.pop_cart,null);
l_finalizar = view.findViewById(R.id.l_finalizar);
l_finalizar.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
pago();
}
});
dialogBuilder.setView(view);
dialog = dialogBuilder.create();
dialog.show();
}
private void pago() {
Intent intent = new Intent(CategoriaActivity.this, PagoActivity.class);
startActivity(intent);
}
}
I dont know whats wrong with the code, the recycle view aint working, it aint showing any items, i would really appreciate if someone could help me out and notice something wrong in my code

Call adapter.notifyDataSetChanged() in your query done callback, this will notify the adapter that the list has changed. This is happening because when you set the adapter, the list was empty as the query was running in background. Once it completes, you have to tell the adapter that new data has been added to list:
if (e == null) {
for (ParseObject obj : objList) {
...
}
adapter.notifyDataSetChanged();
}
Also, create your adapter before you send the query otherwise it may result in NullPointerException in case data is loaded before the next statement executes (highly unlikely but never hurts to be safe).
dbObjects = new ArrayList<>();
adapter = new CategoryRAdapter(this, dbObjects);
ParseQuery<ParseObject> query = ParseQuery.getQuery("Category");

I recommend you to use RxJava2 to user asynchronous methods, it's awesome... And about the problem, maybe your data is not ready when you're already creating the adapter with the ArrayList.
Try to move the recyclerView.setAdapter() to inside the FindCallback after create the Food Objects.

How to delete recycler view item from room database

I am using MVVM architecture model to create an app.I have recycler view in MainActivity and on click of a delete button in recycler view item it should be removed from room database.I know item can be removed within adapter class but as I am using MVVM model I want to carry out delete operation in Repository class.
This is my code below:
UserDao.java
#Dao
public interface UserDao {
#Insert(onConflict = OnConflictStrategy.REPLACE)
void Insert(User... users);
#Query("SELECT * FROM Users")
LiveData<List<User>> getRoomUsers();
#Delete
void Delete(User... user);
}
UserAdapter.java
public class UserAdapter extends
RecyclerView.Adapter<UserAdapter.ViewHolder> {
List<User> userList;
Context context;
public UserAdapter(List<User> userList, Context context) {
this.userList = userList;
this.context = context;
}
#NonNull
#Override
public UserAdapter.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.user_row_layout,parent,false);
ViewHolder viewHolder = new ViewHolder(v);
return viewHolder;
}
#Override
public void onBindViewHolder(#NonNull UserAdapter.ViewHolder holder, int position) {
final User users = userList.get(position);
holder.row_name.setText(users.getName());
holder.row_age.setText(users.getAge());
holder.delete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
}
});
}
#Override
public int getItemCount() {
return userList.size();
}
public void setUserList(List<User> userList) {
this.userList = userList;
notifyDataSetChanged();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView row_name,row_age;
ImageView delete;
public ViewHolder(#NonNull View itemView) {
super(itemView);
row_name = itemView.findViewById(R.id.row_name);
row_age = itemView.findViewById(R.id.row_age);
delete = itemView.findViewById(R.id.delete);
}
}
}
UserRepository.java
public class UserRepository {
private Context context;
private UserDb userDb;
private LiveData<List<User>> listLiveData;
public UserRepository(Context context) {
this.context = context;
userDb = UserDb.getInstance(context);
listLiveData = userDb.userDao().getRoomUsers();
}
public void getUserList(){
Retrofit retrofit = RetrofitClient.getInstance();
ApiService apiService = retrofit.create(ApiService.class);
Call<List<User>> userList = apiService.getUser();
userList.enqueue(new Callback<List<User>>() {
#Override
public void onResponse(Call<List<User>> call, final Response<List<User>> response) {
Completable.fromAction(new Action() {
#Override
public void run() throws Exception {
if(response.body() != null) {
List<User> list = response.body();
for (int i = 0; i < list.size(); i++) {
String id = list.get(i).getId();
String names = list.get(i).getName();
String age = list.get(i).getAge();
User user = new User(id,names,age);
userDb.userDao().Insert(user);
}
}
}
}).subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new CompletableObserver() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onComplete() {
Toast.makeText(context,"Data inserted",Toast.LENGTH_SHORT).show();
}
#Override
public void onError(Throwable e) {
Toast.makeText(context,e.getMessage(),Toast.LENGTH_LONG).show();
}
});
}
#Override
public void onFailure(Call<List<User>> call, Throwable t) {
Toast.makeText(context,t.getMessage(),Toast.LENGTH_LONG).show();
}
});
}
public LiveData<List<User>> getRoomUsers(){
return listLiveData;
}
}
UserViewModel.java
public class UserViewModel extends AndroidViewModel {
private UserRepository repo;
private LiveData<List<User>> listLiveData;
public UserViewModel(#NonNull Application application) {
super(application);
repo = new UserRepository(application);
listLiveData = repo.getRoomUsers();
}
public LiveData<List<User>> getListLiveData() {
return listLiveData;
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity {
UserRepository userRepository;
RecyclerView recyclerView;
UserViewModel userModel;
List<User> userList;
UserAdapter adapter;
ProgressBar prg;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
prg = findViewById(R.id.prg);
userRepository = new UserRepository(this);
userModel = ViewModelProviders.of(this).get(UserViewModel.class);
recyclerView = findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
userList = new ArrayList<>();
adapter = new UserAdapter(userList,this);
recyclerView.setAdapter(adapter);
userModel.getListLiveData().observe(this, new Observer<List<User>>() {
#Override
public void onChanged(List<User> users) {
prg.setVisibility(View.INVISIBLE);
adapter.setUserList(users);
}
});
FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent i = new Intent(MainActivity.this,AddUser.class);
startActivity(i);
}
});
userRepository.getUserList();
}
Someone please let me know how do I implement delete operation. Any help would be appreciated.
THANKS

Firstly, initialize UserViewModel in your adapter class like how you did in MainActivity, then call delete function.
holder.delete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
userModel.deleteItem(users);
}
});
Add this function in UserModel class.
public void deleteItem(User user) = repo.deleteItem(user);
In UserRepository class, call Delete function.
public void deleteItem(User user) {
userDb.userDao().Delete(user);
}

Try to observe changes form the database with live data, whenever you perform anything, adding or deleting(in the database), in your observer refresh that data for the recycler view
Set a click listener to your Adapter
public interface OnListInteractionListener {
// TODO: Update argument type and name
void onListInteraction(User user);
}
In Adapter class
private final OnListInteractionListener mListener;
public UserAdapter(List<User> users, OnListInteractionListener listener,Context context) {
mListener = listener;
}
and in view bind holder
holder.delete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
mListener.onListInteraction(userList.get(position))
}
});
Implement that listener in your activity/fragment and from that, you can access Viewmodel and repo

How can I get a variable from RecyclerView Adapter passed to MainActivity?

I was just playing around with some code, learning new things, when I ran into this problem... I'm trying to pass a variable from my RecylcerViewAdapter to a method in MainActivity, but I just can't seem to accomplish it.
I tried a lot of different thing with interfaces and casting, but nothing did the trick. Since I'm fairly new to all of this, maybe I'm making a trivial mistake somewhere?
My Interface:
public interface AdapterCallback {
void onMethodCallback(int id);
}
This is my adapter class:
public class PostAdapter extends RecyclerView.Adapter<PostAdapter.ViewHolder> {
private List<Post> postList;
private Context context;
private AdapterCallback listener;
public PostAdapter() {
}
public PostAdapter(List<Post> postList, Context context) {
this.postList = postList;
this.context = context;
}
public void setListener(AdapterCallback listener) {
this.listener = listener;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.recycler_layout, viewGroup, false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull final ViewHolder viewHolder, final int position) {
viewHolder.tvTitle.setText(postList.get(position).getTitle());
viewHolder.tvBody.setText(new StringBuilder(postList.get(position).getBody().substring(0, 20)).append("..."));
viewHolder.tvId.setText(String.valueOf(postList.get(position).getUserId()));
viewHolder.parentLayout.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
int id = postList.get(position).getId();
if (listener != null) {
listener.onMethodCallback(id);
}
}
});
}
#Override
public int getItemCount() {
return postList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView tvTitle;
TextView tvBody;
TextView tvId;
LinearLayout parentLayout;
public ViewHolder(View itemView) {
super(itemView);
tvTitle = itemView.findViewById(R.id.tvTitle);
tvBody = itemView.findViewById(R.id.tvBody);
tvId = itemView.findViewById(R.id.tvId);
parentLayout = itemView.findViewById(R.id.parentLayout);
}
}
}
And my MainActivity:
public class MainActivity extends AppCompatActivity {
public static final String TAG = "MainActivityLog";
private CompositeDisposable disposable = new CompositeDisposable();
#BindView(R.id.rvPosts)
RecyclerView rvPosts;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
rvPosts.setHasFixedSize(true);
rvPosts.setLayoutManager(new LinearLayoutManager(this));
populateList();
logItems();
}
private void populateList() {
MainViewModel viewModel = ViewModelProviders.of(MainActivity.this).get(MainViewModel.class);
viewModel.makeQuery().observe(MainActivity.this, new Observer<List<Post>>() {
#Override
public void onChanged(#Nullable List<Post> posts) {
PostAdapter adapter = new PostAdapter(posts, getApplicationContext());
rvPosts.setAdapter(adapter);
}
});
}
public void logItems() {
PostAdapter adapter = new PostAdapter();
adapter.setListener(new AdapterCallback() {
#Override
public void onMethodCallback(int id) {
MainViewModel viewModel = ViewModelProviders.of(MainActivity.this).get(MainViewModel.class);
viewModel.makeSingleQuery(id).observe(MainActivity.this, new Observer<Post>() {
#Override
public void onChanged(#Nullable final Post post) {
Log.d(TAG, "onChanged: data response");
Log.d(TAG, "onChanged: " + post);
}
});
}
});
}
#Override
protected void onDestroy() {
super.onDestroy();
disposable.clear();
}
}
The populateList() method works just fine, but the logItems() method is the problem.
So when i click on a view in RecyclerView I expect the log to output the title, description and ID of the post that was clicked. nut nothing happens...
So, any help would be appreciated.

Make adapter global variable i.e. a field. Use the same object to set every properties.
private PostAdapter adapter;
Replace your logItems method with this:
public void logItems() {
adapter.setListener(new AdapterCallback() {
#Override
public void onMethodCallback(int id) {
MainViewModel viewModel = ViewModelProviders.of(MainActivity.this).get(MainViewModel.class);
viewModel.makeSingleQuery(id).observe(MainActivity.this, new Observer<Post>() {
#Override
public void onChanged(#Nullable final Post post) {
Log.d(TAG, "onChanged: data response");
Log.d(TAG, "onChanged: " + post);
}
});
}
});
}
And populateList with this:
private void populateList() {
MainViewModel viewModel = ViewModelProviders.of(MainActivity.this).get(MainViewModel.class);
viewModel.makeQuery().observe(MainActivity.this, new Observer<List<Post>>() {
#Override
public void onChanged(#Nullable List<Post> posts) {
adapter = new PostAdapter(posts, getApplicationContext());
rvPosts.setAdapter(adapter);
logItems();
}
});
}
And don't call logItems() from onCreate

This is how I implement with my ListAdapters:
public class FeedbackListAdapter extends RecyclerView.Adapter<FeedbackListAdapter.ViewHolder> {
private final ArrayList<Feedback> feedbacks;
private View.OnClickListener onItemClickListener;
private View.OnLongClickListener onItemLongClickListener;
private final Context context;
public FeedbackListAdapter(ArrayList<Feedback> feedbacks, Context context) {
this.feedbacks = feedbacks;
this.context = context;
}
public void setItemClickListener(View.OnClickListener onItemClickListener) {
this.onItemClickListener = onItemClickListener;
}
public void setOnItemLongClickListener(View.OnLongClickListener onItemLongClickListener){
this.onItemLongClickListener = onItemLongClickListener;
}
public class ViewHolder extends RecyclerView.ViewHolder{
final TextView feedback, created, updated;
final LinearLayout mainLayout;
ViewHolder(View iv) {
super(iv);
/*
* Associate layout elements to Java declarations
* */
mainLayout = iv.findViewById(R.id.main_layout);
feedback = iv.findViewById(R.id.feedback);
created = iv.findViewById(R.id.created_string);
updated = iv.findViewById(R.id.updated_string);
}
}
#Override
public int getItemCount() {
return feedbacks.size();
}
#Override
#NonNull
public FeedbackListAdapter.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fragment_feedback_table_row, parent, false);
return new FeedbackListAdapter.ViewHolder(view);
}
#Override
public void onBindViewHolder(final #NonNull FeedbackListAdapter.ViewHolder holder, final int position) {
/*
* Bind data to layout
* */
try{
Feedback feedback = feedbacks.get(position);
holder.feedback.setText(feedback.getContent());
holder.created.setText(feedback.getCreated());
holder.updated.setText(feedback.getUpdated());
holder.mainLayout.setOnClickListener(this.onItemClickListener);
holder.mainLayout.setOnLongClickListener(this.onItemLongClickListener);
holder.mainLayout.setTag(feedback.getDbID());
TypedValue outValue = new TypedValue();
context.getTheme().resolveAttribute(android.R.attr.selectableItemBackground, outValue, true);
holder.mainLayout.setBackgroundResource(outValue.resourceId);
}catch(IndexOutOfBoundsException e){
e.printStackTrace();
}
}
}

In onPopulateList you create an adaptor:
PostAdapter adapter = new PostAdapter(posts, getApplicationContext());
rvPosts.setAdapter(adapter);
However in public void logItems() { you used a different adapter
PostAdapter adapter = new PostAdapter();
adapter.setListener(new AdapterCallback() {
#Override
public void onMethodCallback(int id) {
...
}
});
Therefore the list is being populated with 1 adapter, but you are setting the listener on an unused second adapter.
The fix is to use the same adapter for both. If you make the adapater a field, and don't create a new one inside of logItems, but just set your listener it should work.
i.e.
// as a field in your class
private PostAdapter adapter;
then
// in `populateList()`
adapter = new PostAdapter(posts, getApplicationContext());
rvPosts.setAdapter(adapter);
and
// in `logItems()`
adapter.setListener(new AdapterCallback() {
#Override
public void onMethodCallback(int id) {
...
}
});

In Adapter
public class CustomerListAdapter extends RecyclerView.Adapter<CustomerListAdapter.OrderItemViewHolder> {
private Context mCtx;
ProgressDialog progressDialog;
//we are storing all the products in a list
private List<CustomerModel> customeritemList;
public CustomerListAdapter(Context mCtx, List<CustomerModel> orderitemList) {
this.mCtx = mCtx;
this.customeritemList = orderitemList;
progressDialog = new ProgressDialog(mCtx);
}
#NonNull
#Override
public OrderItemViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(mCtx);
View view = inflater.inflate(R.layout.activity_customer_list, null);
return new OrderItemViewHolder(view, mCtx, customeritemList);
}
#Override
public void onBindViewHolder(#NonNull OrderItemViewHolder holder, int position) {
CustomerModel customer = customeritemList.get(position);
try {
//holder.textViewPINo.setText("PINo \n"+Integer.toString( order.getPINo()));
holder.c_name.setText(customer.getCustomerName());
holder.c_address.setText(customer.getAddress());
holder.c_contact.setText(customer.getMobile());
holder.i_name.setText(customer.getInteriorName());
holder.i_contact.setText(customer.getInteriorMobile());
holder.i_address.setText(customer.getAddress());
} catch (Exception E) {
E.printStackTrace();
}
}
#Override
public int getItemCount() {
return customeritemList.size();
}
class OrderItemViewHolder extends RecyclerView.ViewHolder implements View.OnLongClickListener, View.OnClickListener {
AlertDialog.Builder alert;
private Context mCtx;
TextView c_name, c_contact, c_address, i_name, i_contact, i_address;
TextView OrderItemID, MaterialType, Price2, Qty, AQty;
//we are storing all the products in a list
private List<CustomerModel> orderitemList;
public OrderItemViewHolder(View itemView, Context mCtx, List<CustomerModel> orderitemList) {
super(itemView);
this.mCtx = mCtx;
this.orderitemList = orderitemList;
itemView.setOnClickListener(this);
itemView.setOnLongClickListener(this);
// CatelogOrderDetailModel catelogOrderDetailModel = new CatelogOrderDetailModel();
c_name = itemView.findViewById(R.id.customerName);
c_contact = itemView.findViewById(R.id.contact);
c_address = itemView.findViewById(R.id.address);
i_name = itemView.findViewById(R.id.interiorName);
i_address = itemView.findViewById(R.id.interiorAddress);
i_contact = itemView.findViewById(R.id.interiorContact);
}
#Override
public void onClick(View v) {
int position = getAdapterPosition();
CustomerModel orderitem = this.orderitemList.get(position);
}
#Override
public boolean onLongClick(View v) {
int position = getAdapterPosition();
CustomerModel orderitem = this.orderitemList.get(position);
if (v.getId() == itemView.getId()) {
// showUpdateDeleteDialog(order);
try {
} catch (Exception E) {
E.printStackTrace();
}
Toast.makeText(mCtx, "lc: ", Toast.LENGTH_SHORT).show();
}
return true;
}
}
}

Can't pre-populate Room database and see it on RecyclerView

I am trying to develop an application that uses Room Persistence Database and displays a list on a RecyclerView, I've followed Google's tutorials and everything but I can seem to see the items on the screen, the app doesn't crash or anything just nothing appearing on the scree:
Here is the Data object class:
#Entity(tableName = "region")
public class Region {
#NonNull
#PrimaryKey(autoGenerate = true)
private int mId;
#ColumnInfo(name = "region_name")
private String mRegionName;
#ColumnInfo(name = "association")
private String mAssociation;
#ColumnInfo(name = "season")
private String mSeason;
public Region(#NonNull int id, String regionName, String association, String season) {
mId = id;
mRegionName = regionName;
mAssociation = association;
mSeason = season;
}
#NonNull
public int getId() {
return mId;
}
public void setId(#NonNull int id) {
mId = id;
}
public String getRegionName() {
return mRegionName;
}
public void setRegionName(String regionName) {
mRegionName = regionName;
}
public String getAssociation() {
return mAssociation;
}
public void setAssociation(String association) {
mAssociation = association;
}
public String getSeason() {
return mSeason;
}
public void setSeason(String season) {
mSeason = season;
}
Here is the Data Dao:
#Dao
public interface RegionDao {
#Query("SELECT * FROM region")
List<Region> getAll();
#Insert
void insert(Region... region);
#Query("DELETE FROM region")
void deleteAll();
Here is the Adapter Class:
public class RegionsAdapter extends RecyclerView.Adapter<RegionsAdapter.RegionViewHolder> {
private List<Region> mRegionList;
private Context mContext;
private int mRowLayout;
private RecyclerViewClickListener mListener;
public static class RegionViewHolder extends RecyclerView.ViewHolder{
LinearLayout regionLayout;
TextView regionName, regionAss, regionSeason;
public RegionViewHolder(View v, RecyclerViewClickListener listener){
super(v);
regionLayout = v.findViewById(R.id.region_layout);
regionName = v.findViewById(R.id.region_name);
regionAss = v.findViewById(R.id.region_ass);
regionSeason = v.findViewById(R.id.region_season);
}
}
public void setClickListener(RecyclerViewClickListener recyclerViewClickListener){
mListener = recyclerViewClickListener;
}
public RegionsAdapter(List<Region> regionList, Context context, int rowLayout, RecyclerViewClickListener listener) {
mRegionList = regionList;
mContext = context;
mRowLayout = rowLayout;
mListener = listener;
}
#Override
public RegionsAdapter.RegionViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(mRowLayout, parent, false);
final RegionsAdapter.RegionViewHolder holder = new RegionsAdapter.RegionViewHolder(view, mListener);
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mListener.onClick(v,holder.getLayoutPosition());
}
});
return holder;
}
#Override
public void onBindViewHolder(RegionViewHolder holder, final int position){
holder.regionName.setText(mRegionList.get(position).getRegionName());
holder.regionSeason.setText(mRegionList.get(position).getSeason());
holder.regionAss.setText(mRegionList.get(position).getAssociation());
}
#Override
public int getItemCount() {
return mRegionList.size();
}
And this is the fragment that it is supposed to show the data base on:
public class RegionFragment extends Fragment {
private List<Region> mRegionList;
private RecyclerView mRecyclerView;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.region_fragment, container, false);
//whenever the activity is started, it reads data from database and stores it into
// local array list 'mRegionList'
final AppDatabase db = Room.databaseBuilder(getActivity().getApplicationContext(),
AppDatabase.class,"app_database").allowMainThreadQueries().build();
List<Region> regionList = db.getRegionDao().getAll();
// Initializing the RecyclerView
mRecyclerView = view.findViewById(R.id.region_rv);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity().getApplicationContext()));
RegionsAdapter adapter = new RegionsAdapter(regionList, getActivity().
getApplicationContext(), R.id.region_layout, new RecyclerViewClickListener() {
#Override
public void onClick(View view, int position) {
// Handling what happenes when a card is clicked
// TODO handling
}
});
mRecyclerView.setAdapter(adapter);
return view;
}
This is the AppDatabase Class:
#Database(entities = {Region.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
public abstract RegionDao getRegionDao();
private static AppDatabase sInstance;
static AppDatabase getDatabase(final Context context) {
if (sInstance == null) {
synchronized (AppDatabase.class){
if (sInstance == null) {
sInstance = Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class,
"database").addCallback(sRoomDatabaseCallback).build();
}
}
}
return sInstance;
}
private static RoomDatabase.Callback sRoomDatabaseCallback =
new RoomDatabase.Callback() {
#Override
public void onOpen(#NonNull SupportSQLiteDatabase db) {
super.onOpen(db);
new PopulateDbAsync(sInstance).execute();
}
};
And finally the AsyncClass to pre populate the database:
class PopulateDbAsync extends AsyncTask<Void, Void, Void> {
private final RegionDao mDao;
PopulateDbAsync(AppDatabase db) {
mDao = db.getRegionDao();
}
#Override
protected Void doInBackground(final Void... params) {
mDao.deleteAll();
Region region = new Region(0,"Europe","UEFA","2017/2018");
mDao.insert(region);
region = new Region(1, "Americas","CONCACAF","2017/2018");
mDao.insert(region);
region = new Region(2, "Asia","AFC","2017/2018");
mDao.insert(region);
region = new Region(3, "International","FIFA","2017/2018");
mDao.insert(region);
region = new Region(4, "Other","ConIFA","2017/2018");
mDao.insert(region);
return null;
}

if your id is PrimaryKey(autoGenerate = true), then don't set id in constructor.
update your onCreateView , you are use wrong database.
final AppDatabase db =AppDatabase.getDatabase(getActivity());
List<Region> regionList = db.getRegionDao().getAll();// here you have fire your query in background thread. you can search for that

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

Deleting In Room Database - java

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