Reputation: 511846

Simple Android RecyclerView example

I've made a list of items a few times using Android's RecyclerView, but it is a rather complicated process. Going through one of the numerous tutorials online works (this, this, and this are good), but I am looking a bare bones example that I can copy and paste to get up and running quickly. Only the following features are necessary:

Vertical layout
A single TextView on each row
Responds to click events

Because I have wished for this several times, I finally decided to make the answer below for my future reference and yours.

Upvotes: 264

Answers (13)

Peter

Reputation: 13485

I'm glad I'm not the only one who finds it insane that most of these "minimal" examples involve creating at least 4 different files just to create a simple tool.

Here is a stand-alone activity in Kotlin (built upon this answer from Saifur Rahman Mohsin) that implements a basic recycler view:

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.constraintlayout.widget.ConstraintLayout
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

class ModelDownloaderActivity : AppCompatActivity() {

    val items = (1..50).toList().map { "Item #$it" }
    inner class ItemHolder(view: View, var textField: TextView = view.findViewById(android.R.id.text1)) : RecyclerView.ViewHolder(view)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // Create recycler view, or find it in Activity's XML file if you prefer
        val myLayoutResource: Int? = null // Replace with R.layout.activity_model_downloader if you want to use an XML layout with a recycler view in it
        val recyclerView = myLayoutResource?.let {
            setContentView(it)
            findViewById(R.id.modelRecyclerView) // Replace with ID of your recycler view in layout
        } ?: RecyclerView(this).also { setContentView(ConstraintLayout(this).apply { addView(it) }) }

        // Bind controls to it.
        recyclerView.layoutManager = LinearLayoutManager(this)
        recyclerView.adapter = object : RecyclerView.Adapter<ItemHolder>() {
            override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
                ItemHolder(LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_1, parent, false))
            override fun getItemCount() = items.size
            override fun onBindViewHolder(holder: ItemHolder, position: Int) {
                holder.textField.text = items[position]
                holder.textField.setOnClickListener {
                    Toast.makeText(this@ModelDownloaderActivity, "Clicked $position", Toast.LENGTH_SHORT).show()
                }
            }
        }
    }
}

Upvotes: 1

Hitesh Sahu

Reputation: 45072

Minimal Recycler view ready to use Kotlin template for:

Vertical layout
A single TextView on each row
Responds to click events (Single and LongPress)

I know this is an old thread and so answer here. Adding this answer for future reference:

Add Recycle view in Build dependency

  implementation 'com.google.android.material:material:1.4.0-alpha02'
    // RecyclerView
    implementation "androidx.recyclerview:recyclerview:1.2.0"

Add a recycle view in your layout

   <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/wifiList"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
           />

Create a layout to display list items (list_item.xml)

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <LinearLayout
        android:padding="5dp"
        android:layout_width="match_parent"
        android:orientation="vertical"
        android:layout_height="wrap_content">

        <androidx.appcompat.widget.AppCompatTextView
            android:id="@+id/ssid"
            android:text="@string/app_name"
            android:layout_width="match_parent"
            android:textSize="17sp"
            android:layout_height="wrap_content" />
        
    </LinearLayout>

</androidx.cardview.widget.CardView>

Now create a minimal Adapter to hold data, code here is self-explanatory

 class WifiAdapter(private val wifiList: ArrayList<ScanResult>) : RecyclerView.Adapter<WifiAdapter.ViewHolder>() {

     // holder class to hold reference
    inner class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        //get view reference
        var ssid: TextView = view.findViewById(R.id.ssid) as TextView
    }

     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
         // create view holder to hold reference
         return ViewHolder( LayoutInflater.from(parent.context).inflate(R.layout.list_item, parent, false))
     }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        //set values
        holder.ssid.text =  wifiList[position].SSID
    }

    override fun getItemCount(): Int {
        return wifiList.size
    }
      // update your data
     fun updateData(scanResult: ArrayList<ScanResult>) {
         wifiList.clear()
         notifyDataSetChanged()
         wifiList.addAll(scanResult)
         notifyDataSetChanged()

     }
 }

Add this class to handle Single click and long click events on List Items

import android.content.Context;
import androidx.recyclerview.widget.RecyclerView
import androidx.recyclerview.widget.RecyclerView.OnItemTouchListener
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;

public class RecyclerTouchListener implements RecyclerView.OnItemTouchListener {

    public interface ClickListener {
        void onClick(View view, int position);

        void onLongClick(View view, RecyclerView recyclerView, int position);

    }
    private GestureDetector gestureDetector;
    private ClickListener clickListener;

    public RecyclerTouchListener(Context context, final RecyclerView recyclerView, final ClickListener clickListener) {
        this.clickListener = clickListener;
        gestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
            @Override
            public boolean onSingleTapUp(MotionEvent e) {
                return true;
            }

            @Override
            public void onLongPress(MotionEvent e) {
                View child = recyclerView.findChildViewUnder(e.getX(), e.getY());
                if (child != null && clickListener != null) {
                    clickListener.onLongClick(child,recyclerView,  recyclerView.getChildPosition(child));
                }
            }
        });
    }


    @Override
    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
        View child = rv.findChildViewUnder(e.getX(), e.getY());
        if (child != null && clickListener != null && gestureDetector.onTouchEvent(e)) {
            clickListener.onClick(child, rv.getChildPosition(child));
        }
        return false;
    }

    @Override
    public void onTouchEvent(RecyclerView rv, MotionEvent e) {

    }

    @Override
    public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {

    }

Lastly Set your adapter to Recycler View and add Touch Listener to start intercepting touch event for a single or double tap on list items

    wifiAdapter = WifiAdapter(ArrayList())

    wifiList.apply {
        // vertical layout
        layoutManager = LinearLayoutManager(applicationContext)
        // set adapter
        adapter = wifiAdapter

        // Touch handling
        wifiList.addOnItemTouchListener(RecyclerTouchListener(applicationContext, wifiList, object : RecyclerTouchListener.ClickListener {
            override fun onClick(view: View?, position: Int) {
                Toast.makeText(applicationContext, "RV OnCLickj " + position, Toast.LENGTH_SHORT).show()
            }

            override fun onLongClick(view: View, recyclerView: RecyclerView, position: Int) {
                Toast.makeText(applicationContext, "RV OnLongCLickj " + position, Toast.LENGTH_SHORT).show()
            }
        }
        ))
    }

Bonus: Update Data

wifiAdapter.updateData(mScanResults as ArrayList<ScanResult>)

Result:

Upvotes: 22

Harsh

Reputation: 413

To get started , just to view something in Recycler view

recycler view adapter can be something like this.

class CustomAdapter: RecyclerView.Adapter<CustomAdapter.ViewHolder>() {
    var data =  listOf<String>()
        set(value) {
            field = value
            notifyDataSetChanged()
        }
    override fun getItemCount() =data.size

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.txt.text= data[position]
    }
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(
            LayoutInflater.from(parent.context).inflate(R.layout.item_view, parent, false)
        )
    }


    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView){
        val txt: TextView = itemView.findViewById(R.id.item_text_view)
    }
}

and to attach the adapter to the recycler view and to attach data to adapter

val view = findViewById<RecyclerView>(R.id.recycler_view)                                              
val adapter = CustomAdapter()                                                                          
val data = listOf("text1", "text2", "text3")
adapter.data = data                                                                             
view.layoutManager = LinearLayoutManager(this, RecyclerView.VERTICAL, false)
view.adapter = adapter

Upvotes: 5

Ranjit Barve

Reputation: 41

Dependencies

compile 'com.android.support:appcompat-v7:25.3.1'
compile 'com.android.support:design:25.3.1'
compile 'com.android.support:multidex:1.0.1'
compile 'com.android.support:cardview-v7:25.3.1'
compile 'com.android.support:support-v4:25.3.1'
compile 'com.lguipeng.bubbleview:library:1.0.0'
compile 'com.larswerkman:HoloColorPicker:1.5'
compile 'com.mcxiaoke.volley:library-aar:1.0.0'

One Class For Click Item

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;

public class RecyclerItemClickListener implements RecyclerView.OnItemTouchListener {
    private OnItemClickListener mListener;

    public interface OnItemClickListener {
        public void onItemClick(View view, int position);
    }

    GestureDetector mGestureDetector;

    public RecyclerItemClickListener(Context context, OnItemClickListener listener) {
        mListener = listener;
        mGestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
            @Override
            public boolean onSingleTapUp(MotionEvent e) {
                return true;
            }
        });
    }

    @Override
    public boolean onInterceptTouchEvent(RecyclerView view, MotionEvent e) {
        View childView = view.findChildViewUnder(e.getX(), e.getY());
        if (childView != null && mListener != null && mGestureDetector.onTouchEvent(e)) {
            mListener.onItemClick(childView, view.getChildPosition(childView));
            return true;
        }
        return false;
    }

    @Override
    public void onTouchEvent(RecyclerView view, MotionEvent motionEvent) { }

    @Override
    public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {

    }


}

Second Class RecyclerView

import android.annotation.SuppressLint;
import android.app.ProgressDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.Uri;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.content.LocalBroadcastManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.android.volley.DefaultRetryPolicy;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;

public class SLByTopics extends Fragment {


    public static ArrayList<MByTopics> byTopicsMainArrayList=new ArrayList<>();


    TabRefreshReceiver tabRefreshReceiver;
    RecyclerView recyclerView;
    SAdpByTopics sAdpByTopics;
    public ArrayList<MByTopics> mByTopicsArrayList=new ArrayList<>();
    ProgressDialog progressDialog;

    public SLByTopics(){
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.sl_fragment_by_topics, container, false);

        progressDialog = new ProgressDialog(getActivity());
        if (IsOnline.isNetworkAvailable(getActivity())) {
            getCategoryTree();
        } else{
            IsOnline.showNoInterNetMessage(getActivity());
        }
        tabRefreshReceiver = new TabRefreshReceiver();
       LocalBroadcastManager.getInstance(getContext()).registerReceiver(tabRefreshReceiver, new IntentFilter("BY_TOPICS"));

        setUpView(view);
        return view;
    }

    private void setUpView(View view) {

        recyclerView=(RecyclerView)view.findViewById(R.id.by_topics_list_recyclerView);
        LinearLayoutManager linearLayoutManager=new LinearLayoutManager(getActivity());
        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(linearLayoutManager);
    }

    @Override
    public void onResume() {
        super.onResume();

        recyclerView.addOnItemTouchListener(new RecyclerItemClickListener(getActivity(), new RecyclerItemClickListener.OnItemClickListener() {
            @Override
            public void onItemClick(View view, final int position) {

                if (mByTopicsArrayList.get(position).getChild().size()>0){
                    Intent intent = new Intent(getActivity(), SByTopicCategory.class);
                    intent.putExtra("selectedCategoryName",mByTopicsArrayList.get(position).getCatname());
                    intent.putExtra("jsonData",mByTopicsArrayList.get(position).getMainTopicJson());
                    startActivity(intent);
                    getActivity().overridePendingTransition(R.anim.activity_in, R.anim.activity_out);
                }else {
                    Intent intent = new Intent(getActivity(), SByCategoryQuestionList.class);
                    intent.putExtra("selectedSubCategoryName",mByTopicsArrayList.get(position).getCatname());
                    intent.putExtra("catID",mByTopicsArrayList.get(position).getId());
                    startActivity(intent);
                    getActivity().overridePendingTransition(R.anim.activity_in, R.anim.activity_out);
                }
            }
        }));

    }

    private class TabRefreshReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            try {
                FragmentTransaction ft = getFragmentManager().beginTransaction();
                ft.detach(SLByTopics.this).attach(SLByTopics.this).commit();
                LocalBroadcastManager.getInstance(getContext()).unregisterReceiver(tabRefreshReceiver);
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }

    private void getCategoryTree() {
        progressDialog.setMessage("Please Wait...");
        progressDialog.setCancelable(false);
        progressDialog.show();

        StringRequest stringRequest = new StringRequest(Request.Method.POST, Const.HOSTNAME + Const.STUDENT_GET_CATEGORY_TREE,
                new Response.Listener<String>() {
                    @SuppressLint("LongLogTag")
                    @Override
                    public void onResponse(String response) {
                        try {
                            JSONObject object = new JSONObject(response);
                            String status = object.getString("status");
                            int i = Integer.parseInt(status);

                            switch (i) {

                                case 0:
                                    progressDialog.dismiss();
//                                    Toast.makeText(getActivity(), "getCategorySuccess", Toast.LENGTH_SHORT).show();
                                    Log.e("getCategoryTree Response", "getCategoryTree Response : " + response);

                                    try {    
                                        byTopicsMainArrayList.clear();
                                        JSONArray info = object.getJSONArray("info");
                                        if (info.length() > 0) {
                                            for (i = 0; i < info.length(); i++) {
                                                JSONObject data = info.getJSONObject(i);
                                                MByTopics mByTopics = new MByTopics();
                                                mByTopics.setId(data.getString("id"));
                                                mByTopics.setCatname(data.getString("catname"));
                                                mByTopics.setMainTopicJson(data.toString());

                                                JSONArray topicChildren = data.getJSONArray("children");
                                                ArrayList<SMByTopicCategory> byChildrenArrayList = new ArrayList<>();

                                                for (int j = 0; j < topicChildren.length(); j++) {
                                                    JSONObject topicChildrenData = topicChildren.getJSONObject(j);
                                                    SMByTopicCategory smByTopicCategory = new SMByTopicCategory();
                                                    smByTopicCategory.setId(topicChildrenData.getString("id"));
                                                    smByTopicCategory.setCatname(topicChildrenData.getString("catname"));
                                                    smByTopicCategory.setChildTopicJson(topicChildrenData.toString());

                                                    JSONArray topicChildrenQuestion = topicChildrenData.getJSONArray("children");
                                                    ArrayList<SMByTopicSubCategory> byChildrenSubArrayList = new ArrayList<>();

                                                    for (int k = 0; k < topicChildrenQuestion.length(); k++) {
                                                        JSONObject topicChildrenSubData = topicChildrenQuestion.getJSONObject(k);
                                                        SMByTopicSubCategory smByTopicSubCategory = new SMByTopicSubCategory();
                                                        smByTopicSubCategory.setId(topicChildrenSubData.getString("id"));
                                                        smByTopicSubCategory.setCatname(topicChildrenSubData.getString("catname"));
                                                        smByTopicSubCategory.setChildSubTopicJson(topicChildrenSubData.toString());

                                                        byChildrenSubArrayList.add(smByTopicSubCategory);
                                                    }

                                                    smByTopicCategory.setQuestions(byChildrenSubArrayList);

                                                    byChildrenArrayList.add(smByTopicCategory);
                                                }
                                                mByTopics.setChild(byChildrenArrayList);
                                                byTopicsMainArrayList.add(mByTopics);
                                            }


                                            mByTopicsArrayList.clear();
                                            mByTopicsArrayList=byTopicsMainArrayList;
                                            sAdpByTopics=new SAdpByTopics(mByTopicsArrayList,getActivity());
                                            recyclerView.setAdapter(sAdpByTopics);
                                            sAdpByTopics.notifyDataSetChanged();

                                        }

                                    }catch (Exception e){
                                        e.printStackTrace();
                                    }
                                    break;

                                default:
                                    progressDialog.dismiss();
//                                    Toast.makeText(getActivity(), "getCategoryError : " + response, Toast.LENGTH_SHORT).show();
                                    Log.e("getCategoryTree Not Response", "getCategoryTree Uploading Not Response : " + response);
                            }

                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        progressDialog.dismiss();
                        Log.e("getCategoryTree Error :","getCategoryTree Error :"+error.getMessage());
//                        Toast.makeText(getActivity(), error.getMessage(), Toast.LENGTH_LONG).show();
                    }
                }){

        };/* {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {

                Map<String, String> map = new HashMap<String, String>();
//                map.put("uid", String.valueOf(ConfigManager.getUserId()));
                return map;
            }
        };*/

        stringRequest.setRetryPolicy(new DefaultRetryPolicy(
                0,
                DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));

        RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
        requestQueue.add(stringRequest);
    }
}

Adapter Class For Recycler Item

import android.app.Activity;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.ArrayList;

public class SAdpByTopics extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
        ArrayList<MByTopics> topicsArrayList=new ArrayList<>();
        Activity activity;

     public SAdpByTopics(ArrayList<MByTopics> topicsArrayList,Activity activity){
        this.topicsArrayList=topicsArrayList;
        this.activity=activity;
     }

     @Override
     public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemeView= LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_by_topic_list,parent,false);
        RecyclerView.ViewHolder holder=new Holder(itemeView);
        holder.setIsRecyclable(false);
        return holder;
     }

     @Override
     public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
         final Holder classHolder = (Holder) holder;
         try{
             classHolder.txt_topic_name.setText(topicsArrayList.get(position).getCatname());
         }catch (Exception e){
             e.printStackTrace();
         }
     }

     @Override
     public int getItemCount() {
        return topicsArrayList.size();
     }


class Holder extends RecyclerView.ViewHolder implements View.OnClickListener {
    TextView txt_topic_name;

    public Holder(View itemView) {
        super(itemView);
        txt_topic_name = (TextView) itemView.findViewById(R.id.txt_topic_name);
    }

    @Override
    public void onClick(View v) {

    }
}
}

Module Class

public class MByTopics {

    String id;
    String topicName;
    String catname;
    String MainTopicJson;
    ArrayList<SMByTopicCategory> child;
    ArrayList<SMByTopicSubCategory> questions;

    public void setId(String id){
        this.id=id;
    }
    public String getId(){
        return  id;
    }

    public void setCatname(String catname) {
        this.catname = catname;
    }

    public String getCatname() {
        return catname;
    }

    public void setTopicName(String topicName) {
        this.topicName = topicName;
    }
    public String getTopicName() {
        return topicName;
    }

    public void setChild(ArrayList<SMByTopicCategory> child) {
        this.child = child;
    }

    public String getMainTopicJson() {
        return MainTopicJson;
    }

    public void setMainTopicJson(String mainTopicJson) {
        MainTopicJson = mainTopicJson;
    }

    public ArrayList<SMByTopicCategory> getChild() {
        return child;
    }

    public void setQuestions(ArrayList<SMByTopicSubCategory> questions) {
        this.questions = questions;
    }

    public ArrayList<SMByTopicSubCategory> getQuestions() {
        return questions;
    }

    public ArrayList<MByTopics> getByTopicList() {
        ArrayList<MByTopics> mByTopicsArrayList = new ArrayList<>();

        for (int i=0;i<11;i++){
            MByTopics mQuestionBankCategory=new MByTopics();

            if (i==1 || i== 5|| i==9){
                mQuestionBankCategory.setTopicName("Microeconomics");
            }else  if (i==2 || i== 10|| i==6) {
                mQuestionBankCategory.setTopicName("Macroeconomics");
            }else {
                mQuestionBankCategory.setTopicName("Current Isssues");
            }

            mByTopicsArrayList.add(mQuestionBankCategory);
        }

        return mByTopicsArrayList;
    }

}

Upvotes: 3

Suragch

Reputation: 511846

The following is a minimal example that will look like the following image.

Start with an empty activity. You will perform the following tasks to add the RecyclerView. All you need to do is copy and paste the code in each section. Later you can customize it to fit your needs.

Add dependencies to gradle
Add the xml layout files for the activity and for the RecyclerView row
Make the RecyclerView adapter
Initialize the RecyclerView in your activity

Update Gradle dependencies

Make sure the following dependencies are in your app gradle.build file:

implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support:recyclerview-v7:28.0.0'

You can update the version numbers to whatever is the most current. Use compile rather than implementation if you are still using Android Studio 2.x.

Create activity layout

Add the RecyclerView to your xml layout.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/rvAnimals"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</RelativeLayout>

Create row layout

Each row in our RecyclerView is only going to have a single TextView. Create a new layout resource file.

recyclerview_row.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:padding="10dp">

    <TextView
        android:id="@+id/tvAnimalName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20sp"/>

</LinearLayout>

Create the adapter

The RecyclerView needs an adapter to populate the views in each row with your data. Create a new java file.

MyRecyclerViewAdapter.java

public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder> {

    private List<String> mData;
    private LayoutInflater mInflater;
    private ItemClickListener mClickListener;

    // data is passed into the constructor
    MyRecyclerViewAdapter(Context context, List<String> data) {
        this.mInflater = LayoutInflater.from(context);
        this.mData = data;
    }

    // inflates the row layout from xml when needed
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(R.layout.recyclerview_row, parent, false);
        return new ViewHolder(view);
    }

    // binds the data to the TextView in each row
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        String animal = mData.get(position);
        holder.myTextView.setText(animal);
    }

    // total number of rows
    @Override
    public int getItemCount() {
        return mData.size();
    }


    // stores and recycles views as they are scrolled off screen
    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView myTextView;

        ViewHolder(View itemView) {
            super(itemView);
            myTextView = itemView.findViewById(R.id.tvAnimalName);
            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
        }
    }

    // convenience method for getting data at click position
    String getItem(int id) {
        return mData.get(id);
    }

    // allows clicks events to be caught
    void setClickListener(ItemClickListener itemClickListener) {
        this.mClickListener = itemClickListener;
    }

    // parent activity will implement this method to respond to click events
    public interface ItemClickListener {
        void onItemClick(View view, int position);
    }
}

Notes

Although not strictly necessary, I included the functionality for listening for click events on the rows. This was available in the old ListViews and is a common need. You can remove this code if you don't need it.

Initialize RecyclerView in Activity

Add the following code to your main activity.

MainActivity.java

public class MainActivity extends AppCompatActivity implements MyRecyclerViewAdapter.ItemClickListener {

    MyRecyclerViewAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // data to populate the RecyclerView with
        ArrayList<String> animalNames = new ArrayList<>();
        animalNames.add("Horse");
        animalNames.add("Cow");
        animalNames.add("Camel");
        animalNames.add("Sheep");
        animalNames.add("Goat");

        // set up the RecyclerView
        RecyclerView recyclerView = findViewById(R.id.rvAnimals);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        adapter = new MyRecyclerViewAdapter(this, animalNames);
        adapter.setClickListener(this);
        recyclerView.setAdapter(adapter);
    }

    @Override
    public void onItemClick(View view, int position) {
        Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
    }
}

Notes

Notice that the activity implements the ItemClickListener that we defined in our adapter. This allows us to handle row click events in onItemClick.

Finished

That's it. You should be able to run your project now and get something similar to the image at the top.

Going on

Adding a divider between rows

You can add a simple divider like this

DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),
    layoutManager.getOrientation());
recyclerView.addItemDecoration(dividerItemDecoration);

If you want something a little more complex, see the following answers:

Changing row color on click

See this answer for how to change the background color and add the Ripple Effect when a row is clicked.

Insert single item

Updating rows

See this answer for how to add, remove, and update rows.

Insert single item

This will be the simplest version of the implementation of RecyclerView.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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">

    <androidx.recyclerview.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/recycler_view"/>

</FrameLayout>

list_item_view.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="46dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/textview"
        android:text="TextView"
        android:textSize="16dp" />

</LinearLayout>

CustomAdapter.java

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
  private List<String> data;
  public CustomAdapter (List<String> data){
    this.data = data;
  }

  @Override
  public CustomAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View rowItem = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_view, parent, false);
    return new ViewHolder(rowItem);
  }

  @Override
  public void onBindViewHolder(CustomAdapter.ViewHolder holder, int position) {
    holder.textView.setText(this.data.get(position));
  }

  @Override
  public int getItemCount() {
    return this.data.size();
  }

  public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    private TextView textView;

    public ViewHolder(View view) {
      super(view);
      view.setOnClickListener(this);
      this.textView = view.findViewById(R.id.textview);
    }

    @Override
    public void onClick(View view) {
      Toast.makeText(view.getContext(), "position : " + getLayoutPosition() + " text : " + this.textView.getText(), Toast.LENGTH_SHORT).show();
    }
  }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    RecyclerView recyclerView = findViewById(R.id.recycler_view);
    
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    recyclerView.setAdapter(new CustomAdapter(generateData()));
    recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));
  }

  private List<String> generateData() {
    List<String> data = new ArrayList<>();
    for (int i = 0; i < 100; i++) {
      data.add(String.valueOf(i) + "th Element");
    }
    return data;
  }

}

Upvotes: 19

Greggo

Reputation: 51

implementation androidx.recyclerview:recyclerview:.... It is advised to update to the androidx libraries which are here:

https://developer.android.com/jetpack/androidx/releases/recyclerview

The layout file Widget XML tag then must be updated to: androidx.recyclerview.widget.RecyclerView

Upvotes: 1

Igor Arny

Reputation: 31

You can use abstract adapter with diff utils and filter

SimpleAbstractAdapter.kt

abstract class SimpleAbstractAdapter<T>(private var items: ArrayList<T> = arrayListOf()) : RecyclerView.Adapter<SimpleAbstractAdapter.VH>() {
   protected var listener: OnViewHolderListener<T>? = null
   private val filter = ArrayFilter()
   private val lock = Any()
   protected abstract fun getLayout(): Int
   protected abstract fun bindView(item: T, viewHolder: VH)
   protected abstract fun getDiffCallback(): DiffCallback<T>?
   private var onFilterObjectCallback: OnFilterObjectCallback? = null
   private var constraint: CharSequence? = ""

override fun onBindViewHolder(vh: VH, position: Int) {
    getItem(position)?.let { bindView(it, vh) }
}

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH {
    return VH(parent, getLayout())
}

override fun getItemCount(): Int = items.size

protected abstract class DiffCallback<T> : DiffUtil.Callback() {
    private val mOldItems = ArrayList<T>()
    private val mNewItems = ArrayList<T>()

    fun setItems(oldItems: List<T>, newItems: List<T>) {
        mOldItems.clear()
        mOldItems.addAll(oldItems)
        mNewItems.clear()
        mNewItems.addAll(newItems)
    }

    override fun getOldListSize(): Int {
        return mOldItems.size
    }

    override fun getNewListSize(): Int {
        return mNewItems.size
    }

    override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        return areItemsTheSame(
                mOldItems[oldItemPosition],
                mNewItems[newItemPosition]
        )
    }

    abstract fun areItemsTheSame(oldItem: T, newItem: T): Boolean

    override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        return areContentsTheSame(
                mOldItems[oldItemPosition],
                mNewItems[newItemPosition]
        )
    }

    abstract fun areContentsTheSame(oldItem: T, newItem: T): Boolean
}

class VH(parent: ViewGroup, @LayoutRes layout: Int) : RecyclerView.ViewHolder(LayoutInflater.from(parent.context).inflate(layout, parent, false))

interface OnViewHolderListener<T> {
    fun onItemClick(position: Int, item: T)
}

fun getItem(position: Int): T? {
    return items.getOrNull(position)
}

fun getItems(): ArrayList<T> {
    return items
}

fun setViewHolderListener(listener: OnViewHolderListener<T>) {
    this.listener = listener
}

fun addAll(list: List<T>) {
    val diffCallback = getDiffCallback()
    when {
        diffCallback != null && !items.isEmpty() -> {
            diffCallback.setItems(items, list)
            val diffResult = DiffUtil.calculateDiff(diffCallback)
            items.clear()
            items.addAll(list)
            diffResult.dispatchUpdatesTo(this)
        }
        diffCallback == null && !items.isEmpty() -> {
            items.clear()
            items.addAll(list)
            notifyDataSetChanged()
        }
        else -> {
            items.addAll(list)
            notifyDataSetChanged()
        }
    }
}

fun add(item: T) {
    items.add(item)
    notifyDataSetChanged()
}

fun add(position:Int, item: T) {
    items.add(position,item)
    notifyItemInserted(position)
}

fun remove(position: Int) {
    items.removeAt(position)
    notifyItemRemoved(position)
}

fun remove(item: T) {
    items.remove(item)
    notifyDataSetChanged()
}

fun clear(notify: Boolean=false) {
    items.clear()
    if (notify) {
        notifyDataSetChanged()
    }
}

fun setFilter(filter: SimpleAdapterFilter<T>): ArrayFilter {
    return this.filter.setFilter(filter)
}

interface SimpleAdapterFilter<T> {
    fun onFilterItem(contains: CharSequence, item: T): Boolean
}

fun convertResultToString(resultValue: Any): CharSequence {
    return filter.convertResultToString(resultValue)
}

fun filter(constraint: CharSequence) {
    this.constraint = constraint
    filter.filter(constraint)
}

fun filter(constraint: CharSequence, listener: Filter.FilterListener) {
    this.constraint = constraint
    filter.filter(constraint, listener)
}

fun getFilter(): Filter {
    return filter
}

interface OnFilterObjectCallback {
    fun handle(countFilterObject: Int)
}

fun setOnFilterObjectCallback(objectCallback: OnFilterObjectCallback) {
    onFilterObjectCallback = objectCallback
}

inner class ArrayFilter : Filter() {
    private var original: ArrayList<T> = arrayListOf()
    private var filter: SimpleAdapterFilter<T> = DefaultFilter()
    private var list: ArrayList<T> = arrayListOf()
    private var values: ArrayList<T> = arrayListOf()


    fun setFilter(filter: SimpleAdapterFilter<T>): ArrayFilter {
        original = items
        this.filter = filter
        return this
    }

    override fun performFiltering(constraint: CharSequence?): Filter.FilterResults {
        val results = Filter.FilterResults()
        if (constraint == null || constraint.isBlank()) {
            synchronized(lock) {
                list = original
            }
            results.values = list
            results.count = list.size
        } else {
            synchronized(lock) {
                values = original
            }
            val result = ArrayList<T>()
            for (value in values) {
                if (constraint!=null && constraint.trim().isNotEmpty() && value != null) {
                    if (filter.onFilterItem(constraint, value)) {
                        result.add(value)
                    }
                } else {
                    value?.let { result.add(it) }
                }
            }
            results.values = result
            results.count = result.size
        }
        return results
    }

    override fun publishResults(constraint: CharSequence, results: Filter.FilterResults) {
        items = results.values as? ArrayList<T> ?: arrayListOf()
        notifyDataSetChanged()
        onFilterObjectCallback?.handle(results.count)
    }

}

class DefaultFilter<T> : SimpleAdapterFilter<T> {
    override fun onFilterItem(contains: CharSequence, item: T): Boolean {
        val valueText = item.toString().toLowerCase()
        if (valueText.startsWith(contains.toString())) {
            return true
        } else {
            val words = valueText.split(" ".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
            for (word in words) {
                if (word.contains(contains)) {
                    return true
                }
            }
        }
        return false
    }
  }
}

And extend abstract adapter with implements methods

TasksAdapter.kt

import android.annotation.SuppressLint
  import kotlinx.android.synthetic.main.task_item_layout.view.*

class TasksAdapter(private val listener:TasksListener? = null) : SimpleAbstractAdapter<Task>() {
override fun getLayout(): Int {
    return R.layout.task_item_layout
}

override fun getDiffCallback(): DiffCallback<Task>? {
    return object : DiffCallback<Task>() {
        override fun areItemsTheSame(oldItem: Task, newItem: Task): Boolean {
            return oldItem.id == newItem.id
        }

        override fun areContentsTheSame(oldItem: Task, newItem: Task): Boolean {
            return oldItem.items == newItem.items
        }
    }
}

@SuppressLint("SetTextI18n")
override fun bindView(item: Task, viewHolder: VH) {
    viewHolder.itemView.apply {
        val position = viewHolder.adapterPosition
        val customer = item.customer
        val customerName = if (customer != null) customer.name else ""
        tvTaskCommentTitle.text = customerName + ", #" + item.id
        tvCommentContent.text = item.taskAddress
        ivCall.setOnClickListener {
            listener?.onCallClick(position, item)
        }
        setOnClickListener {
            listener?.onItemClick(position, item)
        }
    }
}

 interface TasksListener : SimpleAbstractAdapter.OnViewHolderListener<Task> {
    fun onCallClick(position: Int, item: Task)
 }
}

Init adapter

mAdapter = TasksAdapter(object : TasksAdapter.TasksListener {
            override fun onCallClick(position: Int, item:Task) {
            }

            override fun onItemClick(position: Int, item:Task) {

            }
        })
rvTasks.adapter = mAdapter

and fill

mAdapter?.addAll(tasks)

add custom filter

mAdapter?.setFilter(object : SimpleAbstractAdapter.SimpleAdapterFilter<MoveTask> {
            override fun onFilterItem(contains: CharSequence, item:Task): Boolean {
                return contains.toString().toLowerCase().contains(item.id?.toLowerCase().toString())
            }
    })

filter data

mAdapter?.filter("test")

Upvotes: 2

Khemraj Sharma

Reputation: 58964

Now you need 1 adapter for all `RecyclerView`

One adapter can be used in for all RecyclerView. So NO onBindViewHolder, No onCreateViewHolder handling.
No code for setting adapter from Java/Kotlin class. Check sample class.
You can set events and custom data for every list by using Binding Adapters.

I show here setting two different RecyclerView by 1 adapter -

activity_home.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <variable
            name="listOne"
            type="java.util.List"/>

        <variable
            name="listTwo"
            type="java.util.List"/>

        <variable
            name="onItemClickListenerOne"
            type="com.ks.nestedrecyclerbindingexample.callbacks.OnItemClickListener"/>

        <variable
            name="onItemClickListenerTwo"
            type="com.ks.nestedrecyclerbindingexample.callbacks.OnItemClickListener"/>

    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.v7.widget.RecyclerView
            rvItemLayout="@{@layout/row_one}"
            rvList="@{listOne}"
            rvOnItemClick="@{onItemClickListenerOne}"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layoutManager="android.support.v7.widget.LinearLayoutManager"
            />

        <android.support.v7.widget.RecyclerView
            rvItemLayout="@{@layout/row_two}"
            rvList="@{listTwo}"
            rvOnItemClick="@{onItemClickListenerTwo}"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layoutManager="android.support.v7.widget.LinearLayoutManager"
            />

    </LinearLayout>

</layout>

You can see I pass list, item layout id and click listener from layout.

rvItemLayout="@{@layout/row_one}"
rvList="@{listOne}"
rvOnItemClick="@{onItemClickListenerOne}"

This custom attributes are created by BindingAdapter.

public class BindingAdapters {
    @BindingAdapter(value = {"rvItemLayout", "rvList", "rvOnItemClick"}, requireAll = false)
    public static void setRvAdapter(RecyclerView recyclerView, int rvItemLayout, List rvList, @Nullable OnItemClickListener onItemClickListener) {
        if (rvItemLayout != 0 && rvList != null && rvList.size() > 0)
            recyclerView.setAdapter(new GeneralAdapter(rvItemLayout, rvList, onItemClickListener));
    }
}

Now from Activity, you pass list, click listener like

HomeActivity.java

public class HomeActivity extends AppCompatActivity {
    ActivityHomeBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = DataBindingUtil.setContentView(this, R.layout.activity_home);
        binding.setListOne(new ArrayList()); // pass your list or set list from response of API
        binding.setListTwo(new ArrayList());
        binding.setOnItemClickListenerOne(new OnItemClickListener() {
            @Override
            public void onItemClick(View view, Object object) {
                if (object instanceof ModelParent) {
                    // TODO: your action here
                }
            }
        });
        binding.setOnItemClickListenerTwo(new OnItemClickListener() {
            @Override
            public void onItemClick(View view, Object object) {
                if (object instanceof ModelChild) {
                    // TODO: your action here  
                }
            }
        });
    }
}

You don't want read too much, directly clone/download full example on from my github repo. And try it yourself.

You can see GeneralAdapter.java in above repo.

If you have problems while setting up data binding, please see this answer.

Upvotes: 3

Hem Shrestha

Reputation: 479

Based on different sources I have created Simple Implementation of RecyclerView using a Simple Library.

Add this line in build.gradle

implementation 'com.hereshem.lib:awesomelib:2.0.1'

AddCreate a RecyclerView by adding MyRecyclerView in activity_main.xml with

<com.hereshem.lib.recycler.MyRecyclerView
        android:id="@+id/recycler"
        app:layoutManager="LinearLayoutManager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

Now in the MainActivity, Create a ViewHolder by passing the name of Class that needs to bind

public static class EVHolder extends MyViewHolder<Events> {
    TextView date, title, summary;
    public EVHolder(View v) {
        super(v);
        date = v.findViewById(R.id.date);
        title = v.findViewById(R.id.title);
        summary = v.findViewById(R.id.summary);
    }
    @Override
    public void bindView(Events c) {
        date.setText(c.date);
        title.setText(c.title);
        summary.setText(c.summary);
    }
}

Create Items list variable and adapters with very few lines by passing items, class and layout in the adapter

List<Events> items = new ArrayList<>();
MyRecyclerView recycler = findViewById(R.id.recycler);
RecyclerViewAdapter adapter = new RecyclerViewAdapter(this, items, EVHolder.class, R.layout.row_event);
recycler.setAdapter(adapter);

ClickListener can be added with following lines

recycler.setOnItemClickListener(new MyRecyclerView.OnItemClickListener() {
    @Override
    public void onItemClick(int position) {
        Toast.makeText(MainActivity.this, "Recycler Item Clicked " + position, Toast.LENGTH_SHORT).show();
    }
});

Its all done.

More example and implementation can be found here . Hope this helps !!!

Upvotes: 4

noone

Reputation: 6558

Since I cant comment yet im gonna post as an answer the link.. I have found a simple, well organized tutorial on recyclerview http://www.androiddeft.com/2017/10/01/recyclerview-android/

Apart from that when you are going to add a recycler view into you activity what you want to do is as below and how you should do this has been described on the link

add RecyclerView component into your layout file
make a class which you are going to display as list rows
make a layout file which is the layout of a row of you list
now we need a custom adapter so create a custom adapter by extending from the parent class RecyclerView.Adapter
add recyclerview into your mainActivity oncreate
adding separators
adding Touch listeners

Upvotes: 2

Simple Android RecyclerView example

Answers (13)

Minimal Recycler view ready to use Kotlin template for:

Update Gradle dependencies

Create activity layout

Create row layout

Create the adapter

Initialize RecyclerView in Activity

Finished

Going on

Further reading

This will be the simplest version of the implementation of RecyclerView.

activity_main.xml

list_item_view.xml

CustomAdapter.java

MainActivity.java

Now you need 1 adapter for all `RecyclerView`

You don't want read too much, directly clone/download full example on from my github repo. And try it yourself.

Related Questions

Simple Android RecyclerView example

Answers (13)

Minimal Recycler view ready to use Kotlin template for:

Update Gradle dependencies

Create activity layout

Create row layout

Create the adapter

Initialize RecyclerView in Activity

Finished

Going on

Further reading

This will be the simplest version of the implementation of RecyclerView.

activity_main.xml

list_item_view.xml

CustomAdapter.java

MainActivity.java

Now you need 1 adapter for all RecyclerView

You don't want read too much, directly clone/download full example on from my github repo. And try it yourself.

Related Questions

Now you need 1 adapter for all `RecyclerView`