Develop Reference

How do I set onClick listener to recyclerView?

I want to add onClick to recyclerView to send data back to form Activity for update data process. How can I implement onItemClickListner when this code doesn't have adapter in it?
Show_Employees.java:
package com.example.roomdatabaseandroid;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
import com.example.roomdatabaseandroid.DataModel.EmployeeDao;
import com.example.roomdatabaseandroid.DataModel.EmployeeDatabase;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
public class ShowEmployees extends AppCompatActivity {
private static final int EDIT_COURSE_REQUEST = 2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show_employees);
RecyclerView recyclerView;
FloatingActionButton fab = findViewById(R.id.idFABAdd);
EmployeeDao employeeDao;
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//starting a new activity for adding a new course and passing a constant value in it.
Intent intent = new Intent(ShowEmployees.this, MainActivity.class);
startActivity(intent);
}
});
employeeDao = EmployeeDatabase.getDBInstance(this).employeeDao();
recyclerView = findViewById(R.id.employeeRecyclerView);
EmployeeRecycler employeeRecycler = new EmployeeRecycler(employeeDao.getAllEmployee());
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(employeeRecycler);
//below method is use to add swipe to delete method for item of recycler view.
new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
#Override
public boolean onMove(#NonNull RecyclerView recyclerView, #NonNull RecyclerView.ViewHolder viewHolder, #NonNull RecyclerView.ViewHolder target) {
return false;
}
#Override
public void onSwiped(#NonNull RecyclerView.ViewHolder viewHolder, int direction) {
//on recycler view item swiped then we are deleting the item of our recycler view.
employeeDao.deleteEmployee(employeeRecycler.data.get(viewHolder.getAdapterPosition()));
Toast.makeText(ShowEmployees.this, "Employee deleted", Toast.LENGTH_SHORT).show();
}
}).attachToRecyclerView(recyclerView);
}
}
Employee_Recycler.java:
package com.example.roomdatabaseandroid;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.example.roomdatabaseandroid.DataModel.DataConverter;
import com.example.roomdatabaseandroid.DataModel.Employee;
import java.util.List;
public class EmployeeRecycler extends RecyclerView.Adapter<EmployeeViewHolder> {
List<Employee> data;
public EmployeeRecycler(List<Employee> employees){
data = employees;
}
#NonNull
#Override
public EmployeeViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(
R.layout.list_item_1,
parent,false
);
return new EmployeeViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull EmployeeViewHolder holder, int position) {
Employee employee = data.get(position);
holder.imageView.setImageBitmap(DataConverter.convertByteArraytoImage(employee.getImage()));
holder.firstName.setText(employee.getFirstName());
holder.middleName.setText(employee.getMiddleName());
holder.lastName.setText(employee.getLastName());
holder.dob.setText(employee.getDOB());
holder.gender.setText(employee.getGender());
holder.address.setText(employee.getAddress());
holder.designation.setText(employee.getDesignation());
holder.email.setText(employee.getEmail());
holder.phoneNumber.setText(employee.getPhoneNumber());
}
#Override
public int getItemCount() {
return data.size();
}
}
EmployeeViewHolder.java:
package com.example.roomdatabaseandroid;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
public class EmployeeViewHolder extends RecyclerView.ViewHolder {
ImageView imageView;
TextView firstName,middleName,lastName,email,phoneNumber,address,designation,gender,dob;
public EmployeeViewHolder(#NonNull View itemView) {
super(itemView);
firstName = itemView.findViewById(R.id.idTVFirstName);
middleName = itemView.findViewById(R.id.idTVMiddleName);
lastName = itemView.findViewById(R.id.idTVLastName);
dob = itemView.findViewById(R.id.idTVDOB);
address = itemView.findViewById(R.id.idTVAddress);
gender = itemView.findViewById(R.id.idTVGender);
designation = itemView.findViewById(R.id.idTVDesignation);
email = itemView.findViewById(R.id.idTVEmail);
phoneNumber = itemView.findViewById(R.id.idTVPhoneNumber);
imageView = itemView.findViewById(R.id.profileImageView);
}
}

add an interface
interface AdapterItemClickListener {
void onItemClickListener(Employee employee, int position)
}
your actvity must implement this interface
public class ShowEmployees extends AppCompatActivity implements AdapterItemClickListener {
private static final int EDIT_COURSE_REQUEST = 2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show_employees);
RecyclerView recyclerView;
FloatingActionButton fab = findViewById(R.id.idFABAdd);
EmployeeDao employeeDao;
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//starting a new activity for adding a new course and passing a constant value in it.
Intent intent = new Intent(ShowEmployees.this, MainActivity.class);
startActivity(intent);
}
});
employeeDao = EmployeeDatabase.getDBInstance(this).employeeDao();
recyclerView = findViewById(R.id.employeeRecyclerView);
EmployeeRecycler employeeRecycler = new EmployeeRecycler(employeeDao.getAllEmployee(), this);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(employeeRecycler);
//below method is use to add swipe to delete method for item of recycler view.
new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
#Override
public boolean onMove(#NonNull RecyclerView recyclerView, #NonNull RecyclerView.ViewHolder viewHolder, #NonNull RecyclerView.ViewHolder target) {
return false;
}
#Override
public void onSwiped(#NonNull RecyclerView.ViewHolder viewHolder, int direction) {
//on recycler view item swiped then we are deleting the item of our recycler view.
employeeDao.deleteEmployee(employeeRecycler.data.get(viewHolder.getAdapterPosition()));
Toast.makeText(ShowEmployees.this, "Employee deleted", Toast.LENGTH_SHORT).show();
}
}).attachToRecyclerView(recyclerView);
}
void onItemClickListener(Employee employee, int position) {
//update or another job
}
}
and your adapter
public class EmployeeRecycler extends RecyclerView.Adapter<EmployeeViewHolder> {
List<Employee> data;
AdapterItemClickListener itemClickListener;
public EmployeeRecycler(List<Employee> employees, AdapterItemClickListener itemClickListener){
data = employees;
this.itemClickListener = itemClickListener;
}
#NonNull
#Override
public EmployeeViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(
R.layout.list_item_1,
parent,false
);
return new EmployeeViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull EmployeeViewHolder holder, int position) {
Employee employee = data.get(position);
holder.imageView.setImageBitmap(DataConverter.convertByteArraytoImage(employee.getImage()));
holder.firstName.setText(employee.getFirstName());
holder.middleName.setText(employee.getMiddleName());
holder.lastName.setText(employee.getLastName());
holder.dob.setText(employee.getDOB());
holder.gender.setText(employee.getGender());
holder.address.setText(employee.getAddress());
holder.designation.setText(employee.getDesignation());
holder.email.setText(employee.getEmail());
holder.phoneNumber.setText(employee.getPhoneNumber());
holder.itemView.setOnClickListener (v -> {
itemClickListener.onItemClickListener(employee, position);
});
}
#Override
public int getItemCount() {
return data.size();
}
}

RecyclerView crashes the application

I was trying to practice using the Recycler in Android Studio using Java.
I have made so much progress so far.
When I run the application it crashes immediately, I have checked the logs and I had an error on the below:
Attempt to invoke virtual method 'android.view.View androidx.recyclerview.widget.RecyclerView.findViewById(int)' on a null object reference
and
Attempt to invoke virtual method 'android.view.View androidx.recyclerview.widget.RecyclerView.findViewById(int)' on a null object reference
Below is my MainActivity class:
package com.example.recyleview;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.widget.LinearLayout;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
private RecyclerView recView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recView.findViewById(R.id.recView);
recView.setLayoutManager(new LinearLayoutManager(this));
setContentView(R.layout.activity_main);
ArrayList<Contact> contacts = new ArrayList<>();
contacts.add(new Contact("Jacob", "jacob#gmail.com", "later"));
contacts.add((new Contact("Sara ", "sara#gmail.com", "later")));
contacts.add(new Contact("Nino", "nino#gmail.com", "later"));
ContactsRecViewAdapter adapter = new ContactsRecViewAdapter(this);
adapter.setContacts(contacts);
recView.setAdapter(adapter);
}
}
and here is another class called ContactsRecViewAdapter
package com.example.recyleview;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
public class ContactsRecViewAdapter extends RecyclerView.Adapter<ContactsRecViewAdapter.ViewHolder>{
private ArrayList<Contact> contacts = new ArrayList<>();
private final Context context;
public ContactsRecViewAdapter(Context context) {
this.context = context;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.contacts_list_item, parent, false);
ViewHolder holder = new ViewHolder(view);
return holder;
}
#Override
public void onBindViewHolder(#NonNull ContactsRecViewAdapter.ViewHolder holder, int position) {
holder.txtName.setText(contacts.get(position).getName());
holder.parent.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(context, contacts.get(position).getName() + " Clicked", Toast.LENGTH_SHORT).show();
}
});
}
#Override
public int getItemCount() {
return contacts.size();
}
public void setContacts(ArrayList<Contact> contacts) {
this.contacts = contacts;
notifyDataSetChanged();
}
public static class ViewHolder extends RecyclerView.ViewHolder{
private final TextView txtName;
private final RelativeLayout parent;
public ViewHolder(#NonNull View itemView) {
super(itemView);
txtName = itemView.findViewById(R.id.txtName);
parent = itemView.findViewById(R.id.parent);
}
}
}

Change
recView.findViewById(R.id.recView);
to
recView = findViewById(R.id.recView);
Also you have duplicated:
setContentView(R.layout.activity_main);
You have to set the contentView before you try to find the views.

A simple implementation of a RecyclerView Listener

I want the app to open a page when the user taps on an item and pass some extra information to that intent. That's it. I tried about 7 - 10 onclickListener types but I didn't solve anything. I am posting my adapter class with the latest implementation ( that doesn't work ). Json works and the Recyclerview loads data and images from url with no problems.
package byDragosT.myapplication;
import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.GridLayout;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.constraintlayout.widget.ConstraintLayout;
import androidx.recyclerview.widget.RecyclerView;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
public class RecipeApiAdapter extends RecyclerView.Adapter<RecipeApiAdapter.RecipeViewHolder> {
private ArrayList<RecipeItem> recipeItems;
private Context context;
public RecipeApiAdapter(ArrayList<RecipeItem> recipeItems, Context context){
this.recipeItems = recipeItems;
this.context = context;
}
#NonNull
#Override //// Mare grija ce layout pui aici - sfat pentru viitor - mi-a luat 4 ore sa gasesc eroarea
public RecipeViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recipe_item_in_recyclerview_api, parent, false);
return new RecipeViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull RecipeViewHolder holder, int position) {
final RecipeItem recipeItem = recipeItems.get(position);
holder.title.setText(recipeItem.getMnameRecipe());
holder.description.setText(recipeItem.getMdescribeRecipe());
Picasso.get().load(recipeItem.getItemPictureUrl())
.into(holder.jpegRecipe);
System.out.println("image with title: " + holder.title.getText() + "was added in theory");
}
#Override
public int getItemCount() {
return recipeItems.size();
}
public static class RecipeViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public ImageView jpegRecipe;
public TextView title;
public TextView description;
public RelativeLayout containerView;
public RecyclerView mRecyclerView;
RecipeViewHolder(View view){
super(view);
jpegRecipe = view.findViewById(R.id.picture);
title = view.findViewById(R.id.recipe_name);
description = view.findViewById(R.id.ingredients_list);
containerView = view.findViewById(R.id.recipe_item_container); // vezi aici
mRecyclerView = view.findViewById(R.id.recyclerView);
}
#Override
public void onClick(View v) {
int itemPosition = mRecyclerView.getChildLayoutPosition(v);
RecipeItem current = recipeItems.get(itemPosition);
Intent intent = new Intent(v.getContext(), RecipeDetailsActivity.class);
intent.putExtra("name", current.getMnameRecipe());
v.getContext().startActivity(intent);
}
}
}

Try adding view.setOnClickListener(this);
RecipeViewHolder(View view){
super(view);
view.setOnClickListener(this);
.....
}

How can i show the recycle view data from listview to next intent activity by id in card view this is my code please check and show the result

How can I show the recycle view data from ListView to next intent activity by id in card view this is my code please check and show the result
import android.content.Context;
import android.content.Intent;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;
import com.bumptech.glide.Glide;
import com.example.tanuj.recycleview.Product;
import com.example.tanuj.recycleview.R;
import java.util.List;
public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ProductViewHolder> {
private TextView textViewTitle,textViewShortDesc,textViewRating,textViewPrice;
private Context mCtx;
private List<Product> productList;
public ProductAdapter(Context mCtx, List<Product> productList) {
this.mCtx = mCtx;
this.productList = productList;
}
#Override
public ProductViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(mCtx);
View view = inflater.inflate(R.layout.product_list, null);
return new ProductViewHolder(view);
}
#Override
public void onBindViewHolder(ProductViewHolder holder, int position) {
Product product = productList.get(position);
Glide.with(mCtx)
.asBitmap()
.load(product.getImage())
.into(holder.imageView);
holder.textViewTitle.setText(product.getTitle());
holder.textViewShortDesc.setText(product.getShortdesc());
holder.textViewRating.setText(String.valueOf(product.getRating()));
holder.textViewPrice.setText(String.valueOf(product.getPrice()));
holder.textViewTitle.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String data = "{}";
Intent intent = new Intent(mCtx,GalleryActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
mCtx.startActivity(intent);
}
});
//Set on click on description
holder.textViewShortDesc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(mCtx,"You are click On Description : " +textViewShortDesc,Toast.LENGTH_SHORT).show();
}
});
//Set on click on price
holder.textViewPrice.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(mCtx,"You are click On Price",Toast.LENGTH_SHORT).show();
}
});
holder.textViewRating.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Toast.makeText(mCtx,"You are click on rating",Toast.LENGTH_SHORT).show();
}
});
}
#Override
public int getItemCount() {
return productList.size();
}
class ProductViewHolder extends RecyclerView.ViewHolder {
TextView textViewTitle, textViewShortDesc, textViewRating, textViewPrice;
ImageView imageView;
public ProductViewHolder(View itemView) {
super(itemView);
textViewTitle = itemView.findViewById(R.id.textViewTitle);
textViewShortDesc = itemView.findViewById(R.id.textViewShortDesc);
textViewRating = itemView.findViewById(R.id.textViewRating);
textViewPrice = itemView.findViewById(R.id.textViewPrice);
imageView = itemView.findViewById(R.id.imageView);
}
}
}

Please make your product class(or model class) implements Parcelable. Android Studio will provide you implementation of parcelable.
Now you can send any your product object in intent extras like Example

Cant go from one activity to another in Recycler View

Hello Every One I am trying to move from one activity to another using intent in adaptor class of recycler view but I am getting son=me errors in doing so, Following are the errors:
1.PakistaniActivity is not a Enclosing class.
2.Cannot resolve method StatrActivity();
Here is my code:
PakistaniActivity.Java
package com.recycler.hp.navigationbar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
public class PakistaniActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pakistani);
RecyclerView rl=findViewById(R.id.list);
rl.setLayoutManager(new LinearLayoutManager(this));
String[] languges={"Badnamiyan", "song2","song3","song4","Song5","song6","song7","song8","song9"};
rl.setAdapter(new Adaptor(languges));
}
}
Adaptor.java
package com.recycler.hp.navigationbar;
import android.content.Intent;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.net.URL;
public class Adaptor extends RecyclerView.Adapter<Adaptor.viewholder> {
private String[] data;
public Adaptor(String[] data) {
this.data = data;
}
#Override
public viewholder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
View view = inflater.inflate(R.layout.list_item1, parent, false);
return new viewholder(view);
}
#Override
public void onBindViewHolder(viewholder holder, final int position) {
String title = data[position];
holder.t.setText(title);
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
long x;
x=getItemId(position);
if(x==0)
{
Intent intent=new Intent(PakistaniActivity.this,Revival_Activity.class);
startActivity(intent);
}
}
});
}
#Override
public int getItemCount() {
return data.length;
}
public class viewholder extends RecyclerView.ViewHolder {
ImageView i;
TextView t;
public viewholder(View itemView) {
super(itemView);
i = itemView.findViewById(R.id.img1);
t = itemView.findViewById(R.id.main1);
}
}
}

Try not starting activities inside the adapter. You can use this adapter:
public abstract class ClickableAdapter<VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH> {
private ClickItemListener clickItemListener;
public void setClickItemListener(ClickItemListener clickItemListener) {
this.clickItemListener = clickItemListener;
}
#Override
public void onBindViewHolder(#NonNull final VH holder, int position) {
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (clickItemListener != null)
clickItemListener.onClickItem(holder.itemView, holder.getAdapterPosition());
else
throw new IllegalStateException("Click listener not set");
}
});
}
public interface ClickItemListener {
void onClickItem(View v, int position);
}
}
Then make your adapter extend mine:
public class Adaptor extends ClickableAdapter<Adaptor.viewholder> {
private String[] data;
public Adaptor(String[] data) {
this.data = data;
}
#Override
public viewholder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
View view = inflater.inflate(R.layout.list_item1, parent, false);
return new viewholder(view);
}
#Override
public void onBindViewHolder(viewholder holder, final int position) {
super.onBindViewHolder(holder,position);
String title = data[position];
holder.t.setText(title);
}
#Override
public int getItemCount() {
return data.length;
}
public class viewholder extends RecyclerView.ViewHolder {
ImageView i;
TextView t;
public viewholder(View itemView) {
super(itemView);
i = itemView.findViewById(R.id.img1);
t = itemView.findViewById(R.id.main1);
}
}
}
Finally in your activity you can set the behaviour for the adapter:
Adaptor adapter = new Adaptor(languges)
rl.setAdapter(adapter);
adapter.setClickItemListener(new ClickableAdapter.ClickItemListener() {
#Override
public void onClickItem(View v, int position) {
if(position==0)
{
Intent intent=new Intent(PakistaniActivity.this,Revival_Activity.class);
startActivity(intent);
}
}
});

Write
Intent intent=new Intent(getContext(),Revival_Activity.class);
startActivity(intent);
instead of this
Intent intent=new Intent(PakistaniActivity.this,Revival_Activity.class);
startActivity(intent);
or
pass the context from the from PakistaniActivity to the Adapter class and user the context as the data member of the adapter class

Pass the context of PakistaniActivity into Adapter
new Adaptor(languges,getApplicationContext);
private Context context;
public Adaptor(String[] data,Conetext context) {
this.data = data;
this.context = conetext;
}
Intent intent=new Intent(context,Revival_Activity.class);
startActivity(intent);

Try using this:
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
long x;
x=getItemId(position);
if(x==0){
Intent intent = new Intent(getContext(), Revival_Activity.class);
context.startActivity(intent);