Develop Reference

Firebase add new child when an item on adapter is non-zero

Hello so I have a function in an app where you will add a data from the adapter if the quantity is non-zero and it will be saved to the firebase realtime database. What i wanna do is if the other item in adapter is non-zero it will add a child to the database but instead firebase is just replacing the item instead of adding a new child what should i do?
here is the code
public class UsualFragRViewAdapter extends RecyclerView.Adapter <UsualFragRViewAdapter.ViewHolder> {
private List<FragmentsUsualModels> items;
private Context context;
public UsualFragRViewAdapter( Context context,List<FragmentsUsualModels> items ) {
this.context = context;
this.items = items;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fragment_usual_array, parent, false);
ViewHolder holder = new ViewHolder(view);
return holder;
}
#Override
public void onBindViewHolder(#NonNull final ViewHolder holder, final int position) {
final FragmentsUsualModels arrayitems = items.get(position);
holder.itemName.setText(arrayitems.getItemName());
holder.price.setText(String.valueOf("$ " +arrayitems.getPrice()));
holder.quantity.setNumber(arrayitems.getQuantity());
holder.card.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
}
});
holder.quantity.setOnValueChangeListener(new ElegantNumberButton.OnValueChangeListener() { //all items are located in its positions
#Override
public void onValueChange(ElegantNumberButton view, int oldValue, int newValue) { //Need to pass all non-zero items as chatview
arrayitems.setQuantity(String.valueOf(newValue));
if (newValue !=0){
String datavalue = holder.itemName.getText().toString();
String dataprice = holder.price.getText().toString();
String dataquantity = holder.quantity.getNumber().toString();
DatabaseReference data = FirebaseDatabase.getInstance().getReference("itemdata");
data.child("dataname").setValue(datavalue);
data.child("dataprice").setValue(dataprice);
data.child("dataquantity").setValue(dataquantity);
Log.d(TAG, "the new value of this data is: " +dataquantity);
Log.d(TAG, "the itemname of this position is: "+datavalue);
Log.d(TAG, "the price of this item in this position is: " +dataprice);
}
Log.d(TAG, "user changed the quantity in this position to " +arrayitems);
}
});
}
#Override
public int getItemCount() {
return items.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
CardView card;
ImageView image;
TextView itemName;
TextView price;
ElegantNumberButton quantity;
Button donebtn;
public ViewHolder(#NonNull View itemView) {
super(itemView);
card = itemView.findViewById(R.id.ucard);
image = itemView.findViewById(R.id.uimage);
itemName = itemView.findViewById(R.id.uitemName);
price = itemView.findViewById(R.id.uprice);
quantity = itemView.findViewById(R.id.uquantity);
donebtn = itemView.findViewById(R.id.udonebtn);
}
}
}

If you want to generate a new child node under a location, call push() on that DatabaseReference. So to create a new child node under itemdata:
DatabaseReference data = FirebaseDatabase.getInstance().getReference("itemdata");
DatabaseReference newData = data.push();
Now you can write the data to this new location as:
newData.child("dataname").setValue(datavalue);
newData.child("dataprice").setValue(dataprice);
newData.child("dataquantity").setValue(dataquantity);
One additional change to consider is the reducing the number of writes. Your current code does a separate setValue() call for each property. This works, but it means that any listeners will get called three times, once for each property.
While this may be what you want, it is quite common to want these writes to appear as one operation. If that is the case, you can perform a single setValue() with:
Map<String,Object> values = new HashMap<>();
values.put("dataname", datavalue);
values.put("dataprice", dataprice);
values.put("dataquantity", dataquantity);
newData.setValue(values);
The end result will be exactly the same as before, but now with a single write operation.

You should use push() to create unique id for database item
dataBase.child(/*CHILD*/).push().setValue(dataValue);

Getting a null object exception when using an interface

I have created a shopping cart via recyclerview. Each viewholder also has a + and - button to add or remove quantity. This functionality is done in the adapter and I have to notify the parent fragment of the updated total amount. This last bit is done via an interface. The problem is, I am getting the following error:
Process: com.ecomm.market, PID: 6630
java.lang.NullPointerException: Attempt to invoke interface method 'void com.ecomm.market.SelectionAdapter$OnUpdateCartListener.onUpdateCart(int)' on a null object reference
at com.ecomm.market.SelectionAdapter$ViewHolder$1.onClick(SelectionAdapter.java:103)
at android.view.View.performClick(View.java:5637)
at android.view.View$PerformClick.run(View.java:22429)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
The selected item and corresponding quantity are stored in a hashmap that I convert to an array to populate the recycler view cart. This is what the relevant part of my main fragment MenuFragment looks like:
// Using the adapter interface to add items to cart and adding up total amount
menuItemAdapter.setOnAddToCartListener(new MenuItemAdapter.OnAddToCartListener() {
#Override
public void onAddToCart(final HashMap selectionItemsHashMap) {
setupSelectionRecycler(menuView);
totalAmount = mapToArray(selectionItemsHashMap);
selectionAdapter = new SelectionAdapter(selectionItemArrayList, selectionItemsHashMap, totalAmount);
selectionRecycler.setAdapter(selectionAdapter);
cartItemsHashmap = selectionItemsHashMap;
selectionAdapter.setUpdateCartListener(new SelectionAdapter.OnUpdateCartListener() {
#Override
public void onUpdateCart(int updatedTotalAmount) {
String stringTotalAmount = Integer.toString(updatedTotalAmount);
Log.d(TAG, "received total:" +stringTotalAmount);
tvTotalAmount.setText("$"+ stringTotalAmount);
totalAmount = updatedTotalAmount;
}
});
}
});
}
And here is an excerpt from my adapter SelectionAdapter:
public class SelectionAdapter extends RecyclerView.Adapter<SelectionAdapter.ViewHolder> {
private static final String TAG = SelectionAdapter.class.getSimpleName();
private ArrayList<SelectionItem> selectionItemArrayList = new ArrayList<>();
public HashMap<String, Integer> selectionItemsHashMap = new HashMap<String, Integer>();
public int totalAmount;
private OnUpdateCartListener updateCartListener;
public interface OnUpdateCartListener {
void onUpdateCart(int totalAmount);
}
public void setUpdateCartListener(OnUpdateCartListener updateCartListener) {
this.updateCartListener = updateCartListener;
}
public SelectionAdapter(ArrayList<SelectionItem> selectionItemArrayList, HashMap<String, Integer> selectionItemsHashMap, int currentTotalAmount) {
this.selectionItemArrayList = selectionItemArrayList;
this.selectionItemsHashMap = selectionItemsHashMap;
this.totalAmount = currentTotalAmount;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int viewType) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.selection_card, viewGroup, false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
#Override
public void onBindViewHolder(#NonNull ViewHolder viewHolder, int position) {
viewHolder.tvSelectItem.setText(selectionItemArrayList.get(position).getSelectionName());
String quantity = Integer.toString(selectionItemArrayList.get(position).getSelectionQuantity());
viewHolder.tvDishQuantity.setText(quantity);
}
#Override
public int getItemCount() {
return selectionItemArrayList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView tvSelectItem, tvDishQuantity;
ImageView addQuantity, subtractQuantity, deleteItem;
public ViewHolder(#NonNull View itemView) {
super(itemView);
tvSelectItem = itemView.findViewById(R.id.dish_selection);
tvDishQuantity = itemView.findViewById(R.id.dish_quantity);
addQuantity = itemView.findViewById(R.id.button_add);
subtractQuantity = itemView.findViewById(R.id.button_subtract);
deleteItem = itemView.findViewById(R.id.delete_item);
addQuantity.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// Find the name of the menu item
int position = getAdapterPosition();
String itemName = selectionItemArrayList.get(position).getSelectionName();
// Increase quantity
int currentQuantity = selectionItemsHashMap.get(itemName);
currentQuantity += 1;
// Update the hashmap with the new quantity
selectionItemsHashMap.put(itemName,currentQuantity);
//Update total amount
for (Object name: selectionItemsHashMap.keySet()) {
String key = (String) name;
if (key.equals(selectionItemArrayList.get(position).getSelectionName())) {
int eachPrice = Integer.parseInt(selectionItemArrayList.get(position).getSelectionPrice());
totalAmount += eachPrice;
}
}
// Display the new quantity
String stringCurrentQuantity = Integer.toString(currentQuantity);
tvDishQuantity.setText(stringCurrentQuantity);
//updateCartListener.onUpdateCart(totalAmount);
}
});
}
EDIT
A couple of points:
- When the cart is initially filled, I use this same code and it works fine.
- The problem occurs once the user returns to the cart and I have to repopulate it from a bundle. Everything works fine, except when the user goes straight to the cart and attempts to alter the quantity from there.

Pass interface implementation into the constructor of Adapter as follows :
public SelectionAdapter(ArrayList<SelectionItem> selectionItemArrayList, HashMap<String, Integer> selectionItemsHashMap, int currentTotalAmount,UpdateCartListener updateCartListener ) {
this.selectionItemArrayList = selectionItemArrayList;
this.selectionItemsHashMap = selectionItemsHashMap;
this.totalAmount = currentTotalAmount;
this.updateCartListener = updateCartListener
}
This will provide an implementation of your interface on the initialization of your adapter so it will be not null when you are using it for update cart.

So you try to access the listener inside the ViewHolder which is probably the cause of the crash, what the standard way is setting the OnClickListener inside your adapter
#Override
public void onBindViewHolder(#NonNull ViewHolder viewHolder, int position) {
viewHolder.tvSelectItem.setText(selectionItemArrayList.get(position).getSelectionName());
String quantity = Integer.toString(selectionItemArrayList.get(position).getSelectionQuantity());
viewHolder.tvDishQuantity.setText(quantity);
viewHolder.addQuantity.setOnClickListener(new View.OnClickListener() {
...
}
}

You need to instantiate your updateCartListener begfore you use it. Do updateCartListener = new WhatverClassThatImplementsYourInterafce() before you use it or make your method to override Default if you are using Java 8 using the new FunctionalInterface in java.util.Function.

I guess you forget assignment the updateCartListener in your adapter.
SelectionAdapter(selectionItemArrayList, selectionItemsHashMap, totalAmount);
cartItemsHashmap = selectionItemsHashMap;
selectionAdapter.setUpdateCartListener(new SelectionAdapter.OnUpdateCartListener() {
#Override
public void onUpdateCart(int updatedTotalAmount) {
String stringTotalAmount = Integer.toString(updatedTotalAmount);
Log.d(TAG, "received total:" +stringTotalAmount);
tvTotalAmount.setText("$"+ stringTotalAmount);
totalAmount = updatedTotalAmount;
}
});
selectionRecycler.setAdapter(selectionAdapter);

How To use Two List<> in One RecyclerView

I have two list<> With different data but that are equal in size , I want to use these two lists in one RecyclerView And I want to fill RecyclerView items using these two lists, but items that are filled with the second list are empty in RecyclerView and Just Items that are filled with the first list are show.
i dont know how to use both List in one recyclerView.
RecyclerViewAdapter :
public class RecyclerViewAdapter_StudentList extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
private List<StudentTable> studentData = new ArrayList<>();//First List
private List<PerformanceTable> performanceData = new ArrayList<>();//Second List
private Context context;
private DatabaseHandler database;
public RecyclerViewAdapter_StudentList(Context context , List<StudentTable> tableData , List<PerformanceTable> performanceData)
{
this.context = context;
this.studentData = tableData;
this.performanceData = performanceData;
database = new DatabaseHandler(context);
}
public class itemHolder extends RecyclerView.ViewHolder
{
TextView studentName ;
TextView studentPositive;
TextView studentNegative;
public itemHolder(View itemView)
{
super(itemView);
studentName = (TextView) itemView.findViewById(R.id.item_txt_StudentList_StudentName);
studentPositive = (TextView) itemView.findViewById(R.id.item_StudentList_Positive);
studentNegative = (TextView) itemView.findViewById(R.id.item_StudentList_Negative);
}
}
#Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(context).inflate(R.layout.recyclerview_item_student_list, parent, false);
return new itemHolder(view);
}
#Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
final itemHolder itemHolder = (itemHolder) holder;
final String studentName = studentData.get(position).getStudentName();
itemHolder.studentName.setText(String.valueOf(studentName));
int pCount = performanceData.get(position).getPositive();
int nCount = performanceData.get(position).getNegative();
itemHolder.studentPositive.setText(String.valueOf(pCount));//These items are empty
itemHolder.studentNegative.setText(String.valueOf(nCount));//These items are empty
.
.
.
}
public int getItemCount()
{
return studentData.size();
}

#Nima Khalili
please go through below links this might what you r asking for.
https://stackoverflow.com/a/26245463/4361438
https://www.journaldev.com/12372/android-recyclerview-example
i will explain it if this will fix your problem.

You can do something like this....
List<Model1> list1 = new ArrayList<>();
List<Model2> list2 = new ArrayList<>();
List<BothModels> list3 = new ArrayList<>();
list1.add(new Model1(whatever here));
//add more to list1
list2.add(new Model2(whatever here));
//add more to list2
list3.addAll(list1);
list3.addAll(list2);
Now that everything is in list3, you can use that list to fill in your recycler view.
Its also possible to achieve it with polymorphism... using an interface. Might actually be a better way now that I think about it. If you have no idea what polymorphism is or if you never created an interface before, I would recommend reading up on it. I wont cover that in this answer.
Here is also another answer this is way better....
https://stackoverflow.com/a/13706974/8200290

Recyclervew clear viewholder when deleting item

file with working code to test my issue, you have to add 2 items, then delete any of those and then add a new one to see how the deleted gets on top of the newly addded
https://www.dropbox.com/s/ojuyz5g5f3kaz0h/Test.zip?dl=0
I have a problem when deleting an item from the recyclerview, when ever I delete an item, IF I add a new item, the deleted item will appear in top of the newly added item, how could I get a fresh view or avod this from happening as is a big issue.
this is how i add items from my main activity
if (!resta || (diff > (3*60*1000)))
{
Ri.add(dataroot);
Integer position = adapter.getItemCount() + 1;
adapter.notifyItemInserted(position);
}
here my Adapter
public class ComandaAdapter extends RecyclerView.Adapter<ComandaAdapter.ComandaAdapterViewHolder>{
private Context mContext;
private ArrayList<Integer> lista_entradas = new ArrayList<>();
private ArrayList<Integer> lista_fondos = new ArrayList<>();
private ArrayList<Integer> lista_postres= new ArrayList<>();
private Boolean primeritem;
private ArrayList<DataRoot> Rir;
private TextView txt_comandas;
private TextView txt_entracola;
private TextView txt_fondocola;
private TextView txt_postrecola;
public ComandaAdapter(Context context, TextView tx_entracola, TextView tx_fondocola, TextView tx_postrecola, TextView tx_comandas, ArrayList<DataRoot> Rir)
{
this.mContext = context;
this.txt_comandas = tx_comandas;
this.txt_entracola = tx_entracola;
this.txt_fondocola = tx_fondocola;
this.txt_postrecola = tx_postrecola;
this.Rir= Rir;
}
#Override
public ComandaAdapter.ComandaAdapterViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
{
return new ComandaAdapter.ComandaAdapterViewHolder(LayoutInflater.from(mContext).inflate(R.layout.row,parent,false));
}
#Override
public void onBindViewHolder(final ComandaAdapter.ComandaAdapterViewHolder holder, final int position)
{
DataRoot Rdata = Rir.get(position);
holder.setdata(Rdata);
}
public void delete(int position)
{
Rir.remove(position);
notifyItemRemoved(position);
}
public class ComandaAdapterViewHolder extends RecyclerView.ViewHolder
{
Button btn_cerrar;
public ComandaAdapterViewHolder(View itemView)
{
super(itemView);
btn_cerrar = (Button) itemView.findViewById(R.id.btn_cerrar);
void setData(final DataRoot Rdata)
{
btn_cerrar.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View view)
{
btn_cerrar.setEnabled(false);
btn_cerrar.setBackgroundTintList(mContext.getColorStateList(R.color.cboff));
updateRetrofitEstadoorden(Rdata.get_id());
updateRetrofitNrocomanda(Rdata.get_id(), txt_comanda.getText().toString());
delete(getAdapterPosition());
}
});
Rdata.gerOrder();
creaboton():
and here my recyler
private void setAdapter()
{
adapter = new ComandaAdapter(this, txt_entracola, txt_fondocola, txt_postrecola, txt_comandas, Ri);
recyclerView.getRecycledViewPool().setMaxRecycledViews(-1, Ri.size());//va en 0 supuestamente -1 es default
recyclerView.setItemViewCacheSize(Ri.size()); //ver si hay que cambiar con cada item
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(adapter);
}
Thanks in advance for any help.
Images to show the problem

You are using the Recyclerview in a very non standard way. The issue you are seeing is because the views are being recycled (as they should be in a Recyclerview) but you are not clearing out the items from the previous view.
The problem in in this method:
public void setData(String value) {
container.removeAllViews(); // Remove all previously added views
textview.setText(value);
Random r = new Random();
int i1 = r.nextInt(5 - 1) + 1;
for (int i = 0; i < i1; i++) {
be = new Button(mContext);
be.setText("Boton " + i);
be.setLayoutParams(new LinearLayout.LayoutParams(240, LinearLayout.LayoutParams.WRAP_CONTENT));
container.addView(be);
}
}
By calling container.addView(be), you are manually adding extra views to the views that the Recyclerview creates. When you remove these views, they are cached and reused the next time you press "Add". The problem is that the cached view still contains all of the manually added views so you are then adding more views under the existing ones.
As you can see in the code above, i added container.removeAllViews(); which removes the views that were added previously ensuring that "Container" is empty before you start adding your extra views to it.
Also, unless you have a very specific reason for doing so, I would removes these lines as I believe you are hurting performance by having them:
list.getRecycledViewPool().setMaxRecycledViews(-1, index);
list.setItemViewCacheSize(index);

Data on recycleview item is not correct when scroll

My adapter code:
public class BrandAdapter extends RecyclerView.Adapter<BrandAdapter.BrandViewHolder> {
private static final String TAG = BrandAdapter.class.getSimpleName();
private List<BrandItem> brands;
private Context context;
public BrandAdapter(Context context, List<BrandItem> data) {
this.context = context;
this.brands = data;
}
public void setData(List<BrandItem> dataDownload) {
this.brands = dataDownload;
}
#Override
public BrandViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_item_brand, null);
BrandViewHolder holder = new BrandViewHolder(view);
return holder;
}
#Override
public void onBindViewHolder(BrandViewHolder holder, int position) {
BrandItem brandItem = brands.get(position);
String name = brandItem.getName();
int count = brandItem.getCountArticles();
holder.tvName.setText(name);
if (count > 0) {
holder.tvCount.setText("" + count);
} else {
holder.tvCount.setVisibility(View.GONE);
}
}
#Override
public int getItemCount() {
return brands.size();
}
public static class BrandViewHolder extends RecyclerView.ViewHolder {
TextView tvName;
TextView tvCount;
public BrandViewHolder(View itemView) {
super(itemView);
tvName = (TextView) itemView.findViewById(R.id.tv_brand_name);
tvCount = (TextView) itemView.findViewById(R.id.tv_count_article);
}
}
}
Fragment code :
recyclerView = (RecyclerView) view.findViewById(R.id.recycleView);
linearLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(linearLayoutManager);
adapter = new BrandAdapter(getActivity(), brands);
recyclerView.setAdapter(adapter);
Data for brands is downloaded from server. After downloaded finished, I just set new data for adapter by this code :
brands = downloadedBrands();
adapter.setData(brands);
adapter.notifyDataSetChanged();
Everything is Ok when data loaded for first time after the download finish. But when I scroll down the recycleview and scroll up again, data for each item is wrong now, all textview tvCount is gone. I do not know why.
Is there any problem from my code ?

Greenrobo's answer is correct but here is an explanation as to WHY you are having this issue.
You are assuming that your view is always set to the default values in your onBindViewHolder method.
The RecyclerView re-uses views that have scrolled off screen and therefore the view you are binding to may have already been previously used (and changed).
You onBindViewHolder method should always set EVERYTHING up. i.e all views reset to the exact values you want and do not assume that because you default an item to visible, it will always be so.

Please make tvCount visible when setting a non-zero count.
if (count > 0) {
holder.tvCount.setText("" + count);
holder.tvCount.setVisibility(View.VISIBLE);
} else {
holder.tvCount.setVisibility(View.GONE);
}
See if this helps.

You told that if count is less than 0, hide the view. What if count is greater than zero ? You are not making the view visible again. So simply make the below changes in your if condition:
if (count > 0) {
holder.tvCount.setText("" + count);
holder.tvCount.setVisibility(View.VISIBLE);
} else {
holder.tvCount.setVisibility(View.GONE);
}