1. Entity (table) CurrentyEntity.java
@Entity(tableName = "Corona")
public class CurrentyEntity {
@PrimaryKey(autoGenerate = true)
private int id;
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
@NonNull
@ColumnInfo (name = "country")
private String country;
@NonNull
public String getCountry() {
return this.country;
}
@ColumnInfo (name = "infections_count")
private int infections_count;
public int getInfections_count() {
return this.infections_count;
}
public CurrentyEntity (@NonNull String country, int infections_count){
this.country = country;
this.infections_count = infections_count;
}
@Ignore
public CurrentyEntity (int id, String country , int infections_count){
this.id = id;
this.country = country;
this.infections_count = infections_count;
}
}
2. Dao PlayerDao.class
import java.util.List;
@Dao
public interface PlayerDao {
@Insert(onConflict = OnConflictStrategy.IGNORE)
void insert(CurrentyEntity player);
@Update
void update(CurrentyEntity...players);
// how to delete a column value for a row
@Delete
void delete(CurrentyEntity player);
// how to return a specific row ??
@Query("SELECT * FROM Corona ORDER BY infections_count ASC ")
LiveData<List<CurrentyEntity>> returnRowLowToHigh();
@Query("SELECT COUNT(*) FROM Corona")
Integer getRowCount();
}
3. Room Database RoomDB.class
@Database(entities = {CurrentyEntity.class}, version = 2, exportSchema = false)
public abstract class RoomDB extends RoomDatabase {
public abstract PlayerDao PlayerDao();
private static RoomDB INSTANCE;
public static RoomDB getINSTANCE(final Context context){
if (INSTANCE == null)
{
synchronized (RoomDB.class)
{
if (INSTANCE == null)
{
INSTANCE = Room.databaseBuilder(context.getApplicationContext(), RoomDB.class,"pumpin_DataBase")
// Wipes and rebuilds instead of migrating
// if no Migration object.
// Migration is not part of this practical.
.fallbackToDestructiveMigration()
.addCallback(afterOpeningRoomDB)
.build();
}
}
}
return INSTANCE;
}
// // the only 2 callback methods
// //void onCreate(SupportSQLiteDatabase db)
// //Called when the database is created for the first time.
// //
// //void onOpen(SupportSQLiteDatabase db)
// //Called when the database has been opened.
private static RoomDatabase.Callback afterOpeningRoomDB = new RoomDatabase.Callback(){
@Override
public void onOpen(@NonNull SupportSQLiteDatabase db) {
super.onOpen(db);
new LaunchAsyncTask(INSTANCE).execute();
}
};
private static class LaunchAsyncTask extends AsyncTask<Void,Void,Void>{
private final PlayerDao DAO;
public LaunchAsyncTask(RoomDB db){
DAO = db.PlayerDao();
}
@Override
protected Void doInBackground(final Void... voids) {
DAO.insert(new CurrentyEntity("jordan",3434));
return null;
}
}
}
4. Repository AllRepository.class
public class AllRepository {
private PlayerDao playerDao;
private LiveData<List<CurrentyEntity>> rowList;
private static String rowCount;
AllRepository(Application application){
RoomDB roomdb = RoomDB.getINSTANCE(application);
playerDao = roomdb.PlayerDao();
rowList = playerDao.returnRowLowToHigh();
}
LiveData<List<CurrentyEntity>> returnRowList () {return rowList;}
public void RemoveRow(CurrentyEntity row){ new removeRow(playerDao).execute(row);}
public void AddRow(CurrentyEntity row) { new addRow(playerDao).execute(row);}
public void UpdateRow(CurrentyEntity row){ new updateRow(playerDao).execute(row);}
public String getRowCount(){ new getRowCount(playerDao).execute();
return rowCount; }
private static class removeRow extends AsyncTask<CurrentyEntity,Void,Void> {
private PlayerDao removePlayerDao;
public removeRow(PlayerDao currentDao){
removePlayerDao = currentDao;
}
@Override
protected Void doInBackground(CurrentyEntity... players) {
removePlayerDao.delete(players[0]);
return null;
}
}
private static class addRow extends AsyncTask<CurrentyEntity,Void,Void> {
private PlayerDao addPlayerDao;
public addRow(PlayerDao currentDao){
addPlayerDao = currentDao;
}
@Override
protected Void doInBackground(CurrentyEntity... players) {
addPlayerDao.insert(players[0]);
return null;
}
}
private static class updateRow extends AsyncTask<CurrentyEntity,Void,Void> {
private PlayerDao updatePlayerDao;
public updateRow(PlayerDao currentDao){
updatePlayerDao = currentDao;
}
@Override
protected Void doInBackground(CurrentyEntity... players) {
updatePlayerDao.update(players[0]);
return null;
}
}
private static class getRowCount extends AsyncTask<CurrentyEntity,Void,Void> {
private PlayerDao addPlayerDao;
public getRowCount(PlayerDao currentDao){
addPlayerDao = currentDao;
}
@Override
protected Void doInBackground(CurrentyEntity... players) {
rowCount = String.valueOf(addPlayerDao.getRowCount());
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
}
}
**5. ViewModel AllViewModel.class **
public class AllViewModel extends AndroidViewModel {
private AllRepository allRepository;
private LiveData<List<CurrentyEntity>> rowList;
public AllViewModel( Application application) {
super(application);
allRepository = new AllRepository(application);
rowList = allRepository.returnRowList();
}
LiveData<List<CurrentyEntity>> returnRowList(){ return rowList;}
public void removeRow(CurrentyEntity row){ allRepository.RemoveRow(row);}
public void addRow(CurrentyEntity row){ allRepository.AddRow(row);}
public void updateRow(CurrentyEntity row){ allRepository.UpdateRow(row);}
public String getRowCount(){ return allRepository.getRowCount();}
}
6. RecyclerView Adapter MenWomenRecycler.class
public class MenWomenRecycler extends RecyclerView.Adapter<MenWomenRecycler.MenWomenViewHolder> {
private final LayoutInflater mInflater;
private List<CurrentyEntity> listOfCases;
MenWomenRecycler(Context context) {
mInflater = LayoutInflater.from(context);
}
public void setList(List<CurrentyEntity> incomingList ){
listOfCases = incomingList;
notifyDataSetChanged();
}
@NonNull
@Override
public MenWomenViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = mInflater.inflate(R.layout.view_holder_men_women, parent, false);
return new MenWomenViewHolder(itemView);
}
@Override
public void onBindViewHolder(@NonNull MenWomenViewHolder holder, int position) {
CurrentyEntity currentCase = listOfCases.get(position);
TextView first = holder.cardView.findViewById(R.id.men_women_count);
first.setText(currentCase.getCountry());
TextView secound = holder.cardView.findViewById(R.id.men_women_country);
secound.setText(Integer.toString(currentCase.getInfections_count()));
// Warning : maybe I shouldve used String.format instead
}
// if this is set to 0 it fucks up the whole thing. RecyclerView'ss contents won't be displayed
// getItemCount() is called many times, and when it is first called,
// mWords has not been updated (means initially, it's null, and we can't return null).
@Override
public int getItemCount() {
if(listOfCases != null){
Log.w("Row Count", String.valueOf(listOfCases.size()));
return listOfCases.size();
} else return 0;
}
class MenWomenViewHolder extends RecyclerView.ViewHolder {
/* private final TextView Country;
private final TextView count;
Country = itemView.findViewById(R.id.men_women_country);
count = itemView.findViewById(R.id.men_women_count);
*/
private CardView cardView;
public MenWomenViewHolder(@NonNull View itemView) {
super(itemView);
cardView = (CardView) itemView;
}
}
}
**7. HomeActivity.Class **
public class HomeActivity extends AppCompatActivity {
private Button signout;
private AllViewModel viewModel;
private RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
recyclerView = findViewById(R.id.men_women_recycler);
final MenWomenRecycler adapter = new MenWomenRecycler(this);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
Log.w("look for this in the log", "touchin when kb is null");
viewModel = ViewModelProviders.of(this).get(AllViewModel.class);
viewModel.returnRowList().observe(this,new Observer<List<CurrentyEntity>>() {
@Override
public void onChanged(@Nullable final List<CurrentyEntity> listOfCases) {
adapter.setList(listOfCases);
}
});
String rowCount = String.valueOf(viewModel.getRowCount());
viewModel.addRow(new CurrentyEntity("EASY", 23));
viewModel.addRow(new CurrentyEntity("letsee", 233));
** 8. HomeActivity's XML Layout File**
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".HomeActivity">
<!-- tools:listitem="@layout/view_holder_men_women"
this makes it possible to have a preview of the RecyclerView-->
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/men_women_recycler"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
tools:listitem="@layout/view_holder_men_women"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:id="@+id/SIGNOUT"
android:text="@string/signOut"
/>
</LinearLayout>
Here is the problem: first of all lets exclude these 2 lines of code from HomeActivity.class
viewModel.addRow(new CurrentyEntity("EASY", 23));
viewModel.addRow(new CurrentyEntity("letsee", 233));
and stick with the first statemment that inserts a row in RoomDB.class which is this
DAO.insert(new CurrentyEntity("jordan",3434));
so far things work fine, they recycler would only display a single View(viewHolder) Now lets reinclude the 2 lines we've excluded above from the HomeActivity.class and by adding them again RecyclerView would display a random number of views and that number is bigger than the number of rows in RoomDB
For example when I ran the app and launched it RecyclerView supposedly must displaly exactly 3 Views(ViewHolders) as I've inserted only 3 rows, instead it displayed 6 views.
