Develop Reference

How to update previous Items in Android Recycler view?

I have a RecyclerView to list a set of data. And on clicking each item , I have validation to check previous item is entered or not. If that item is not entered I want to enable an inline error (which is hidden in normal case) message in the previous row. I have done the scenario as shown below but error is showing only in the current row. Anyone suggest how I can enable/update previous row or a specific row.
public boolean _validateListItems(int itemIndex)
{
int previousItemIndex = itemIndex - 1;
for (int i = 0; i <= previousItemIndex; i++)
{
if ((listRecyclerItem.get(i).getEnable()==0))
{
return false;
}
}
return true;
}
holder.expand_button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(position>0){
if(_validateListItems(position))
{
mExpandedPosition = isExpanded ? -1:position;
notifyItemChanged(previousExpandedPosition);
notifyItemChanged(position);
notifyDataSetChanged();
}
else
{
holder.error.setVisibility(View.VISIBLE);
holder.error.setTextColor(ContextCompat.getColor(context, R.color.error_red));
}
}
}
});

First of all RecyclerView is something that recycle view. View is generated is based on Data Model.
So, lets store the user button/checkbox click/checked action) to the respective Model/Item. To run the validation, get the items from the Adapter and check your conditions in Activity/Fragment [Looping is an expensive operation, use Coroutine or RxJava]. Execute your validation and if Validation is true for an item, just update the Item from the list and finally update the Adapter. You can pass the Error message in the item and render it to the View. And finally, must use DiffUtil to update the items in adapter.

Declare an interface for your adapter that has callback to your viewModel and when each item changed you can return the call back ito viewmodel and store it in an object or array
for example :
interface Callback { void onDataChanged(int itemPosition); }
call that method in onBindViewHolder when your item text changed
and in view model add the returned item into a list
when you clicked on a button, you can check the items if your necessary item didn't exist you can return error

Disable click on ListView Row with condition

Good morning,
I have a ListView in a first activity (main_activity), when I click on a selected item, I have a new activity (details_activity) that opens with more informations and details, and the user had to check it, then the (details_activity) is closed and back to the main_activity with the same list.
I want to disable the click on listView's rows that are already checked by the user.
I tried to get the position from main_activity to details_activity to use it in SQL to get the informations, it's working.
Then I sent it back, in the main_activity I used this code:
mPrr = getSharedPreferences("reponse",Context.MODE_PRIVATE);
int IDs = mPrr.getInt("ID",-1);
String rep =mPrr.getString("reponse","");
if(IDs != -1) {
lst.getChildAt(IDs).setFocusable(false);
}
Is there any help please?

Create a ArrayList in adapter than whenever perform click on that row check that row position if position not in list than add position to the array list and perform click else nothing to do.
private ArrayList<String> positionClicked = new ArrayList<>();
public void onBindViewHolder(final MyViewHolder holder, final int position) {
if (!positionClicked.contains(String.valueOf(position))) {
positionClicked.add(String.valueOf(position));
//perform Click
}else {
//
}
}

Write setClickable(false) instead of setFocusable(false);

Create custom ArrayAdapter, find the position of item you want to disable click and #Overide isEnabled method
#Override
public boolean isEnabled(int position) {
if(position == positionYouWannaDisableClick)
return false;
return true;
}

Save position of specific item in RecyclerView after new data insertion

I implement RecyclerView which have two ViewType. The list is dynamic and when user scroll down/up it add some items. In my RecyclerView just one of the item has different ViewType (consider this as expandable list which only one of item expand at a time).
I save position for expanded item But when new data added this position changed and I lost expanded item. Because data added in scroll down/up, updating expanded item according to size of new data is not good Idea.
One thing to mention is that I want to scroll to expanded item at first load. so I guess saving position would be best choice. (I guess but I'm not sure);
I want to know what's the efficient way to handle this issue?

http://tutorials.jenkov.com/java-collections/hashcode-equals.html
Implement hashcode and equals method, using this get the position for the expanded model object.
Example :
public class Employee {
protected long employeeId;
protected String firstName;
protected String lastName;
public boolean equals(Object o){
if(o == null) return false;
if(!(o instanceof) Employee) return false;
Employee other = (Employee) o;
if(this.employeeId != other.employeeId) return false;
if(! this.firstName.equals(other.firstName)) return false;
if(! this.lastName.equals(other.lastName)) return false;
return true;
}
public int hashCode(){
return (int) employeeId;
}
}
// To get the index of expanded item
int expandedItemIndex = EmployeeList.indexOf(expandedEmployeeModel);
recyclerView.scrollToPosition(expandedItemIndex);

Likely you use model for loading data to RecyclerView. And this model (for ex. ContactModel) contains different values for your ViewHolders.
What is point, that you use special references for that saved position. What you need to do, it's just put that position (of expanded item) to current model. And after all most works fine.

RecyclerView.Adapter onBindViewHolder() gets wrong position

I'll show the code and after the steps to get the problem.
I have a recyclerview inside a tabbed fragment that takes the dataset from a custom object:
mRecyclerView = (RecyclerView) v.findViewById(R.id.recyclerview);
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerAdapter = new MyRecyclerAdapter(mMes.getListaItens(), this, getActivity());
mRecyclerView.setAdapter(mRecyclerAdapter);
I set the longclick behavior of the list items in onBindViewHolder() of the adapter:
#Override
public void onBindViewHolder(final ViewHolder holder, final int position) {
ItemMes item = mListaItens.get((position));
holder.descricao.setText(item.getDescrição());
holder.valor.setText(MainActivity.decimalFormatWithCod.format(item.getValor()));
...
holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
new MaterialDialog.Builder(mContext)
.title(holder.descricao.getText().toString())
.items(R.array.opcoes_longclick_item)
.itemsCallbackSingleChoice(-1, new MaterialDialog.ListCallbackSingleChoice() {
#Override
public boolean onSelection(MaterialDialog dialog, View view, int which, CharSequence text) {
switch (which) {
case 0:
mParentFragment.showUpdateItemDialog(position);
return true;
case 1:
mParentFragment.showDeleteItemDialog(position);
return true;
}
return false;
}
})
.show();
return true;
}
});
}
Then, the methods in the fragment that take care of delete the item itself:
public void showDeleteItemDialog(int position) {
final ItemMes item = mMes.getListaItens().get(position);
new MaterialDialog.Builder(getActivity())
.title("Confirmar Remoção")
.content("Tem certeza que deseja remover " + item.getDescrição() + "?")
.positiveText("Sim")
.negativeText("Cancelar")
.onPositive(new MaterialDialog.SingleButtonCallback() {
#Override
public void onClick(#NonNull MaterialDialog dialog, #NonNull DialogAction which) {
deleteItem(item);
}
})
.show();
}
public void deleteItem(ItemMes item) {
getMainActivity().deleteItemFromDatabase(item.getID());
int position = mMes.getListaItens().indexOf(item);
mMes.getListaItens().remove(position);
mRecyclerAdapter.notifyItemRemoved(position);
atualizaFragment();
}
And finally the method in activity that do the DB operation:
public int deleteItemFromDatabase(long id) {
SQLiteDatabase db = dataBaseHelper.getWritableDatabase();
String where = DBHelper.COLUNA_ID + " = ?";
String[] args = {String.valueOf(id)};
int rowsAffected = db.delete(DBHelper.TABELA_ITEM, where, args);
db.close();
return rowsAffected;
}
Now i'll reproduce the steps:
I'm showing 3 itens in the listview. Then I try to remove the first:
1 - The longclick is intercepted passing the correct index:
2 - The item is correctly deleted from the database:
3 - After all this, as expected, the adapter is storing and showing 2 items...
SO, if I try to delete the first item of this 2 item list I get the wrong position (should be 0, is 1):
And also if I try to delete the last item of this 2 item list I get the wrong position (should be 1, is 2):
The question is: If I have a dataset of size 2 (and the adapter knows it), how can it call onBindViewHolder(ViewHolder holder, int [last index +1])?
I have no idea what could be wrong. So I ask help cause I'm thinking about give up this project cause I do everything right but always something dont works, and Im tired.
Thanks in advance.

I've noticed that in method onBindViewHolder(VH holder, int position) while the position was comming wrong, the holder.getAdapterPosition() gives me always the correct position.
So I changed my code from:
ItemMes item = mListaItens.get((position));
...
mParentFragment.showUpdateItemDialog(position);
...
mParentFragment.showDeleteItemDialog(position);
....
To:
ItemMes item = mListaItens.get((holder.getAdapterPosition()));
...
mParentFragment.showUpdateItemDialog(holder.getAdapterPosition());
...
mParentFragment.showDeleteItemDialog(holder.getAdapterPosition());
....
And everything works well. This is very strange but...
Thanks everybody.

Took a look at the adapter code you provided in the comment and it's pretty straightforward. Try this: rather than call notifyItemRemoved(), call notifyDataSetChanged(). This is rather expensive as it will cause your adapter to re-bind the data set (and re-create ViewHolders), but since you're using an ArrayList where you are removing an element, it's really the simplest way to do it. Otherwise you'll have to track the position of the items and when an item is removed it cannot change the position of other items - or handle the case where items shift their position in the data set.

Try this code in onBindViewHolder()
int adapterPos=holder.getAdapterPosition();
if (adapterPos<0){
adapterPos*=-1;
}
ItemMes item = mListaItens.get((adapterPos));
mParentFragment.showUpdateItemDialog(adapterPos);
Use adapterPos instead of position variable.

According to RecyclerView's getAdapterPosition documentation:
RecyclerView does not handle any adapter updates until the next layout traversal. This
may create temporary inconsistencies between what user sees on the screen and what
adapter contents have. This inconsistency is not important since it will be less than
16ms but it might be a problem if you want to use ViewHolder position to access the
adapter. Sometimes, you may need to get the exact adapter position to do
some actions in response to user events. In that case, you should use this method which
will calculate the Adapter position of the ViewHolder.
So in case of implementing user events, using getAdapterPosition is a recommended way to go.

How to check a record is existed in database inside getItemViewType

I have a list of products, each row has a function "Save" which will store the item product to local database. I'm using SwipeMenuListView via https://github.com/baoyongzhang/SwipeMenuListView and i have to check record is existed or not in getItemViewType in ListAdapter to remove function Save of the row which saved.
But the problem is, the "check record is existed or not" made my listview freeze after notifyDataSetChanged for a while (click "Save" then notifyDataSetChanged then list is freezed until i touch listview again).
How should i fix it?
Every suggestion will be highly appreciated. Thanks in advance. Here is my code:
#Override
public boolean onMenuItemClick(int position, SwipeMenu menu, int index) {
switch (index) {
case 0:
break;
case 1:
ProductDetailsVo.ProductInfo productInfo = listResult.get(position);
insertProductToDB(productInfo);
break;
}
and method insertProductToDB:
private void insertProductToDB(ProductDetailsVo.ProductInfo productInfo) {
databaseManager.insertProductToDB(productInfo);
if (adapter != null) {
adapter.notifyDataSetChanged();
}
}
Adapter:
#Override
public int getViewTypeCount() {
return 2;
}
#Override
public int getItemViewType(int position) {
if (databaseManager.isProductSaved(listProds.get(position).getProductId())) {// cause listview freeze
return 1;
}
return 0;
}

So the freezes are probably due the numerous calls to isProductSaved, you can be sure of that by commenting them and test, or by profiling your app with the Android Device Monitor.
You can easily remove that database access by adding a field exists to your products. The default value would be false and insertProductToDB would set it to true if the insertion succeeds. With that your getViewType will be much faster.
#Override
public int getItemViewType(int position) {
if (listProds.get(position).isExists())) {
return 1;
}
return 0;
}
If you don't want to alter your model object with an extra field, you can also maintain a map like a SparseArray in the adapter. It would contain the id of the saved products.