How to update RecyclerView Adapter Data in Android?

AndroidApps/ApplicationsMobile Development

Before getting into example, we should know what is Recycler view in android. Recycler view is more advanced version of list view and it works based on View holder design pattern. Using recycler view we can show grids and list of items.

This example demonstrate about how to update Recycler View adapter by creating a beautiful student records app that displays student name with age.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Open build.gradle and add Recycler view & Card view library dependencies.

apply plugin: 'com.android.application'

android {
   compileSdkVersion 28
   defaultConfig {
      applicationId "com.example.andy.tutorialspoint"
      minSdkVersion 19
      targetSdkVersion 28
      versionCode 1
      versionName "1.0"
      testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
   }
   buildTypes {
      release {
         minifyEnabled false
         proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
      }
   }
}
dependencies {
   implementation fileTree(dir: 'libs', include: ['*.jar'])
   implementation 'com.android.support:appcompat-v7:28.0.0'
   implementation 'com.android.support:design:28.0.0'
   implementation 'com.android.support.constraint:constraint-layout:1.1.3'
   implementation 'com.android.support:cardview-v7:28.0.0'
   implementation 'com.android.support:recyclerview-v7:28.0.0'
   testImplementation 'junit:junit:4.12'
   androidTestImplementation 'com.android.support.test:runner:1.0.2'
   androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

Step 3 − Add the following code to res/layout/activity_main.xml.

<?xml version = "1.0" encoding = "utf-8"?>
<RelativeLayout
   xmlns:android = "http://schemas.android.com/apk/res/android"
   xmlns:tools = "http://schemas.android.com/tools"
   xmlns:app = "http://schemas.android.com/apk/res-auto"
   android:layout_width = "match_parent"
   android:layout_height = "match_parent"
   app:layout_behavior = "@string/appbar_scrolling_view_behavior"
   tools:showIn = "@layout/activity_main"
   tools:context = ".MainActivity">
   <android.support.v7.widget.RecyclerView
      android:id = "@+id/recycler_view"
      android:layout_width = "match_parent"
      android:layout_height = "wrap_content"
      android:layout_marginBottom = "50dp"
      android:scrollbars = "vertical" />
   <LinearLayout
      android:layout_width = "match_parent"
      android:layout_below = "@+id/recycler_view"
      android:layout_marginTop = "-50dp"
      android:layout_alignParentBottom = "true"
      android:layout_height = "wrap_content">
      <Button
         android:id = "@+id/add"
         android:layout_width = "wrap_content"
         android:layout_height = "wrap_content"
         android:text = "add item"/>
      <Button
         android:id = "@+id/remove"
         android:layout_width = "wrap_content"
         android:text = "remove item"
         android:layout_height = "wrap_content" />
   </LinearLayout>
</RelativeLayout>

In the above code we have added recycler view to window manger as relative parent layout and added two buttons as add and remove. Add button going to add the data to recyclerview adpter and remove button going to remove data from recyclerview.

Step 4 − Add the following code to src/MainActivity.java

package com.example.andy.tutorialspoint;

import android.annotation.TargetApi;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;


public class MainActivity extends AppCompatActivity {
   private RecyclerView recyclerView;
   private StudentAdapter studentAdapter;
   private List studentDataList = new ArrayList<>();
   @TargetApi(Build.VERSION_CODES.O)
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      Button add = findViewById(R.id.add);
      Button remove = findViewById(R.id.remove);
      recyclerView = findViewById(R.id.recycler_view);
      studentAdapter = new StudentAdapter(studentDataList,MainActivity.this);
      RecyclerView.LayoutManager manager = new LinearLayoutManager(this);
      recyclerView.setLayoutManager(manager);
      recyclerView.setAdapter(studentAdapter);
      StudentDataPrepare();
      remove.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            if(studentDataList.size()>0) {
               studentDataList.remove(studentDataList.size() - 1);
               studentAdapter.notifyDataSetChanged();
               Toast.makeText(MainActivity.this, String.valueOf(studentDataList.size()), Toast.LENGTH_LONG).show();
            }
         }
      });
      add.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            if(studentDataList.size()> = 0) {
               studentData data = new studentData("raghu ram", 25);
               studentDataList.add(studentDataList.size(), data);
               studentAdapter.notifyDataSetChanged();
               Toast.makeText(MainActivity.this, String.valueOf(studentDataList.size()), Toast.LENGTH_LONG).show();
            }
         }
      });
   }
   @RequiresApi(api = Build.VERSION_CODES.N)
   private void StudentDataPrepare() {
      studentData data = new studentData("sai", 25);
      studentDataList.add(data);
      data = new studentData("sai raj", 25);
      studentDataList.add(data);
      data = new studentData("raghu", 20);
      studentDataList.add(data);
      data = new studentData("raj", 28);
      studentDataList.add(data);
      data = new studentData("amar", 15);
      studentDataList.add(data);
      data = new studentData("bapu", 19);
      studentDataList.add(data);
      data = new studentData("chandra", 52);
      studentDataList.add(data);
      data = new studentData("deraj", 30);
      studentDataList.add(data);
      data = new studentData("eshanth", 28);
      studentDataList.add(data);
      Collections.sort(studentDataList, new Comparator() {
         @Override
         public int compare(studentData o1, studentData o2) {
            return o1.name.compareTo(o2.name);
         }
      });
   }
}

In the above code we have added recycler view and studentAdapter. In that student adapter we have passed studentDatalist as arraylist. In Student data list contains name of the student and age. We have added two buttons as add and remove. Using add button we can add item to array list as shown below -

if(studentDataList.size()> = 0) {
   studentData data = new studentData("raghu ram", 25);
   studentDataList.add(studentDataList.size(), data);
   studentAdapter.notifyDataSetChanged();
   Toast.makeText(MainActivity.this, String.valueOf(studentDataList.size()), Toast.LENGTH_LONG).show();
}

In the above code we are checking validation as if arraylist size is equal to zero or greater than zero than we are added data to array list and we have used on special method as notifyDataSetChanged(). This method indicates to adapter as data set is modified so adapter going to refresh the view internally.

To remove the data from array list we have used remove() with arraylist as shown below -

if(studentDataList.size()>0) {
   studentDataList.remove(studentDataList.size() - 1);
   studentAdapter.notifyDataSetChanged();
   Toast.makeText(MainActivity.this, String.valueOf(studentDataList.size()), Toast.LENGTH_LONG).show();
}

In the above code we are removing data based on size-1. means it going to remove the data from bottom. After removed the data, we are updating to adapter using notifyDataSetChanged().

Step 5 − Following is the content of the modified file src/ StudentAdapter.java.

package com.example.andy.tutorialspoint;

import android.graphics.Color;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.util.List;
import java.util.Random;

class StudentAdapter extends RecyclerView.Adapter<StudentAdapter.MyViewHolder> {
   List<studentData> studentDataList;
   public StudentAdapter(List<studentData> studentDataList) {
      this.studentDataList = studentDataList;
   }
   @NonNull
   @Override
   public MyViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
      View itemView = LayoutInflater.from(viewGroup.getContext())
      .inflate(R.layout.student_list_row, viewGroup, false);
      return new MyViewHolder(itemView);
   }
   @Override
   public void onBindViewHolder(MyViewHolder viewHolder, int i) {
      studentData data = studentDataList.get(i);
      Random rnd = new Random();
      int currentColor = Color.argb(255, rnd.nextInt(256), rnd.nextInt(256), rnd.nextInt(256));
      viewHolder.parent.setBackgroundColor(currentColor);
      viewHolder.name.setText(data.name);
      viewHolder.age.setText(String.valueOf(data.age));
   }
   @Override
   public int getItemCount() {
      return studentDataList.size();
   }
   class MyViewHolder extends RecyclerView.ViewHolder {
      TextView name,age;
      LinearLayout parent;
      public MyViewHolder(View itemView) {
         super(itemView);
         parent = itemView.findViewById(R.id.parent);
         name = itemView.findViewById(R.id.name);
         age = itemView.findViewById(R.id.age);
      }
   }
}   

In the adapter class we have four methods as shown below -

  • onCreateViewHolder() :- It is used to create a view holder and it returns a view.

  • onBindViewHolder() - it going to bind with created view holder.

  • getItemCount() - it contains size of list.

  • MyViewHolder class- it is view holder inner class which is extended by RecyclerView.ViewHolder

To set random background for recycler view items, we have generated random colors using random class(which is predefined class in Android) and added color to parent of view item as shown below -

Random rnd = new Random();
int currentColor = Color.argb(255, rnd.nextInt(256), rnd.nextInt(256), rnd.nextInt(256));
viewHolder.parent.setBackgroundColor(currentColor);

Step 6 − Following is the modified content of the xml res/layout/student_list_row.xml.

<?xml version = "1.0" encoding = "utf-8"?>
<android.support.v7.widget.CardView xmlns:android = "http://schemas.android.com/apk/res/android"
   xmlns:card_view = "http://schemas.android.com/apk/res-auto"
   android:layout_width = "match_parent"
   card_view:cardCornerRadius = "4dp"
   android:id = "@+id/card_view"
   android:layout_margin = "10dp"
   android:layout_height = "200dp">
   <LinearLayout
      android:id = "@+id/parent"
      android:layout_gravity = "center"
      android:layout_width = "match_parent"
      android:orientation = "vertical"
      android:gravity = "center"
      android:layout_height = "match_parent">
   <TextView
      android:id = "@+id/name"
      android:layout_width = "wrap_content"
      android:gravity = "center"
      android:textSize = "25sp"
      android:textColor = "#FFF"
      android:layout_height = "wrap_content" />
   <TextView
      android:id = "@+id/age"
      android:layout_width = "wrap_content"
      android:gravity = "center"
      android:textSize = "25sp"
      android:textColor = "#FFF"
      android:layout_height = "wrap_content" />
   </LinearLayout>
</android.support.v7.widget.CardView>

In the above list item view we have created two text views for name and age inside the cardview. Card view contains pre defined corner radius and shadow property. So we have used corner radius with card view.

Step 7 − Following is the content of the modified file src/ studentData.java.

package com.example.andy.tutorialspoint;

class studentData {
   String name;
   int age;
   public studentData(String name, int age) {
      this.name = name;
      this.age = age;
   }
}

In the above code informs about student data object. Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −

Intially end of the element is sai raj with age 25 now adding two elements as shown below -

Now removing all elements so output should be like this -

Click here to download the project code

raja
Published on 29-Jan-2019 16:43:09
Advertisements