How to update Recyclerview using DiffUtil in Android Studio (Java)
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Step 1: Create a new layout for an item in my case I named it item_contact.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:background="@color/white"
android:layout_marginBottom="4dp"
android:layout_height="wrap_content">
<TextView
android:id="@+id/id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="24dp"
android:textSize="16sp"
android:textStyle="bold"
android:textColor="@color/black"
android:text="TextView"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="24dp"
android:layout_marginBottom="24dp"
android:textSize="14sp"
android:textColor="@color/black"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/id" />
<Button
android:id="@+id/delete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="24dp"
android:text="Delete"
app:layout_constraintBottom_toBottomOf="@+id/name"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="@+id/id" />
</androidx.constraintlayout.widget.ConstraintLayout>
Step 2: Create a new model class in my case I named it Contact.java and implement an interface "Comparable" and implement its method "compareTo"
package com.ashish.diffutilsrecyclerview;
import java.util.ArrayList;
public class Contact implements Comparable {
private String id;
private String name;
private String mobile;
public Contact(String id, String name, String mobile) {
this.id = id;
this.name = name;
this.mobile = mobile;
}
public Contact() {
}
public ArrayList<Contact> getContactList() {
ArrayList<Contact> contact = new ArrayList<Contact>();
contact.add(new Contact("1","Ashish","987"));
contact.add(new Contact("2","sdf","786"));
contact.add(new Contact("3","sdfg","786"));
contact.add(new Contact("4","Assdfghish","76786"));
contact.add(new Contact("5","dfg","976787"));
contact.add(new Contact("6","sdf","987867"));
contact.add(new Contact("7","hth","988677"));
contact.add(new Contact("8","rrrd","45"));
contact.add(new Contact("9","fdgd","634"));
contact.add(new Contact("10","Ashrrvish","987"));
contact.add(new Contact("11","rgr","453"));
contact.add(new Contact("12","Asrtyhish","453"));
contact.add(new Contact("13","rty","8675"));
return contact;
}
public ArrayList<Contact> getUpdateContactList() {
ArrayList<Contact> contact = getContactList();
contact.get(2).setName("dfghdfgh");
contact.get(8).setMobile("1111");
contact.get(9).setMobile("1111");
return contact;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getMobile() {
return mobile;
}
public void setMobile(String mobile) {
this.mobile = mobile;
}
@Override
public int compareTo(Object o) {
Contact contact = (Contact) o;
if (contact.getName().equals(this.name) && contact.getMobile().equals(this.mobile)){
return 0;
}
return 1;
}
}
Step 3: Create a new DiffUtil Callback class in my case I name it MyDiffUtilsCallbacks.java and extend it with class "DiffUtil.Callback" and implement its method "getOldListSize", "getNewListSize", "areItemsTheSame", "areContentsTheSame" and "getChangePayload"
package com.ashish.diffutilsrecyclerview;
import android.os.Bundle;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.DiffUtil;
import java.util.ArrayList;
public class MyDiffUtilsCallbacks extends DiffUtil.Callback {
ArrayList<Contact> oldContacts;
ArrayList<Contact> newContacts;
public MyDiffUtilsCallbacks(ArrayList<Contact> oldContacts, ArrayList<Contact> newContacts) {
this.oldContacts = oldContacts;
this.newContacts = newContacts;
}
@Override
public int getOldListSize() {
return oldContacts !=null ? oldContacts.size() : 0;
}
@Override
public int getNewListSize() {
return newContacts != null ? newContacts.size() : 0;
}
@Override
public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
return true;
}
@Override
public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
int result = newContacts.get(newItemPosition).compareTo(oldContacts.get(oldItemPosition));
if (result==0){
return true;
}
return false;
}
@Nullable
@Override
public Object getChangePayload(int oldItemPosition, int newItemPosition) {
Contact newContact = newContacts.get(newItemPosition);
Contact oldContact = oldContacts.get(oldItemPosition);
Bundle bundle = new Bundle();
if (!newContact.getName().equals(oldContact.getName())){
bundle.putString("name",newContact.getName());
}
if (!newContact.getMobile().equals(oldContact.getMobile())){
bundle.putString("mobile",newContact.getMobile());
}
if (bundle.size()==0){
return null;
}
return bundle;
}
}
Step 4: Create a new Recyclerview Adapter class in my case I named it ContactAdapter.java and extend it with the class "RecyclerView.Adapter" and implement its method "onCreateViewHolder", "onBindViewHolder(@NonNull ContactViewHolder holder, int position)", "onBindViewHolder(@NonNull ContactViewHolder holder, int position, @NonNull List<Object> payloads)", "getItemCount", "getItemCount",
package com.ashish.diffutilsrecyclerview;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.DiffUtil;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
import java.util.List;
public class ContactAdapter extends RecyclerView.Adapter<ContactAdapter.ContactViewHolder> {
private ArrayList<Contact> contactArrayList;
public ContactAdapter(ArrayList<Contact> contactArrayList) {
this.contactArrayList = contactArrayList;
}
@NonNull
@Override
public ContactViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
return new ContactViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_contact, parent, false));
}
@Override
public void onBindViewHolder(@NonNull ContactViewHolder holder, int position) {
Contact contact = contactArrayList.get(position);
holder.mobile.setText(contact.getMobile());
holder.name.setText(contact.getName());
holder.button.setOnClickListener(v -> {
//code here
});
}
@Override
public void onBindViewHolder(@NonNull ContactViewHolder holder, int position, @NonNull List<Object> payloads) {
if (payloads.isEmpty()) {
super.onBindViewHolder(holder, position, payloads);
}else {
Bundle bundle = (Bundle) payloads.get(0);
for (String key : bundle.keySet()){
if (key.equals("name")){
holder.name.setText(bundle.getString("name"));
}
if (key.equals("mobile")){
holder.mobile.setText(bundle.getString("mobile"));
}
}
}
}
@Override
public int getItemCount() {
return contactArrayList.size();
}
public static class ContactViewHolder extends RecyclerView.ViewHolder {
private TextView name;
private TextView mobile;
private Button button;
public ContactViewHolder(@NonNull View itemView) {
super(itemView);
name = itemView.findViewById(R.id.name);
mobile = itemView.findViewById(R.id.id);
button = itemView.findViewById(R.id.delete);
}
}
public void updateContact(ArrayList<Contact> newContactList) {
DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(new MyDiffUtilsCallbacks(contactArrayList,newContactList));
diffResult.dispatchUpdatesTo(this);
contactArrayList.clear();
contactArrayList.addAll(newContactList);
}
}
Step 5: Our activity_main.xml looks like this
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
tools:context=".MainActivity">
<Button
android:id="@+id/refresh"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:text="Refresh"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerview"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginTop="2dp"
tools:listitem="@layout/item_contact"
android:background="#E6E6E6"
android:layout_marginBottom="16dp"
app:layout_constraintBottom_toTopOf="@+id/refresh"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
Step 6: Our MainActivity.java looks like this
package com.ashish.diffutilsrecyclerview;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerview;
private ContactAdapter contactAdapter;
private Button refreshButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerview = findViewById(R.id.recyclerview);
refreshButton = findViewById(R.id.refresh);
recyclerview.setLayoutManager(new LinearLayoutManager(this));
contactAdapter = new ContactAdapter(new Contact().getContactList());
recyclerview.setAdapter(contactAdapter);
refreshButton.setOnClickListener(v ->{
contactAdapter.updateContact(new Contact().getUpdateContactList());
});
}
}
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