A basic example to demonstrate how RecyclerViews can be used

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright 2016 Farbod Salamat-Zadeh
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
      http://www.apache.org/licenses/LICENSE-2.0
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  -->

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            style="@style/AppStyle.Toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </android.support.design.widget.AppBarLayout>

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

ExampleAdapter.java

/*
 * Copyright 2016 Farbod Salamat-Zadeh
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.yourcompany.yourapp;

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 ExampleAdapter extends RecyclerView.Adapter<ExampleAdapter.ExampleViewHolder> {

    public class ExampleViewHolder extends RecyclerView.ViewHolder {
        
        TextView text1, text2;

        ExampleViewHolder(View itemView) {
            super(itemView);
            text1 = (TextView) itemView.findViewById(R.id.text1);
            text2 = (TextView) itemView.findViewById(R.id.text2);
        }
    }

    private ArrayList<CustomClass> mCustomObjects;

    public ExampleAdapter(ArrayList<CustomClass> arrayList) {
        mCustomObjects = arrayList;
    }

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

    @Override
    public ExampleViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_2, parent, false);
        return new ExampleViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ExampleViewHolder holder, int position) {
        CustomClass object = mCustomObjects.get(position);

        // My example assumes CustomClass objects have getFirstText() and getSecondText() methods
        String firstText = object.getFirstText()
        String secondText = object.getSecondText()

        holder.text1.setText(firstText);
        holder.text2.setText(secondText);
    }

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);
    }

}

ExampleClickAdapter.java

/*
 * Copyright 2016 Farbod Salamat-Zadeh
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.yourcompany.yourapp;

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 ExampleClickAdapter extends RecyclerView.Adapter<ExampleClickAdapter.ExampleClickViewHolder> {

    public class ExampleClickViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        
        TextView text1, text2;

        ExampleClickViewHolder(View itemView) {
            super(itemView);
            itemView.setOnClickListener(this);
            title = (TextView) itemView.findViewById(android.R.id.text1);
            subtitle = (TextView) itemView.findViewById(android.R.id.text2);
        }

        @Override
        public void onClick(View v) {
            // The user may not set a click listener for list items, in which case our listener
            // will be null, so we need to check for this
            if (mOnEntryClickListener != null) {
                mOnEntryClickListener.onEntryClick(v, getLayoutPosition());
            }
        }
    }

    private ArrayList<CustomClass> mCustomObjects;

    public ExampleClickAdapter(ArrayList<CustomClass> arrayList) {
        mCustomObjects = arrayList;
    }

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

    @Override
    public ExampleClickViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_2, parent, false);
        return new ExampleClickViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ExampleClickViewHolder holder, int position) {
        CustomClass object = mCustomObjects.get(position);

        // My example assumes CustomClass objects have getFirstText() and getSecondText() methods
        String firstText = object.getFirstText()
        String secondText = object.getSecondText()

        holder.text1.setText(firstText);
        holder.text2.setText(secondText);
    }

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);
    }


    private OnEntryClickListener mOnEntryClickListener;

    public interface OnEntryClickListener {
        void onEntryClick(View view, int position);
    }

    public void setOnEntryClickListener(OnEntryClickListener onEntryClickListener) {
        mOnEntryClickListener = onEntryClickListener;
    }

}

RecyclerViewActivity.java

/*
 * Copyright 2016 Farbod Salamat-Zadeh
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
package com.yourcompany.yourapp;

import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.View;

import java.util.ArrayList;

public class RecyclerViewActivity extends AppCompatActivity {

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

        // Setting up the Toolbar
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        assert getSupportActionBar() != null;
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        

        // Setting up the RecyclerView
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        assert recyclerView != null;
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        
        // Getting your ArrayList - this will be up to you
        ArrayList<CustomClass> yourObjects = getMyObjects();
        
        
        // Standard RecyclerView implementation

        ExampleAdapter adapter = new ExampleAdapter(yourObjects);
        recyclerView.setAdapter(adapter);
        
        
        // OR RecyclerView with a click listener
        
        ExampleClickAdapter clickAdapter = new ExampleClickAdapter(yourObjects);
        clickAdapter.setOnEntryClickListener(new ExampleClickAdapter.OnEntryClickListener() {
            @Override
            public void onEntryClick(View view, int position) {
                // stuff that will happen when a list item is clicked
            }
        });
        recyclerView.setAdapter(clickAdapter);
    }

    private ArrayList<CustomClass> getMyObjects() {
        // This will return the ArrayList of your CustomClass objects
    }

}

It is good.

I implemented everything but i got an error on loading the screen.

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.example.alaincheng.loginapp.ExampleClickAdapter.onBindViewHolder(ExampleClickAdapter.java:77)
at com.example.alaincheng.loginapp.ExampleClickAdapter.onBindViewHolder(ExampleClickAdapter.java:29)
at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6673)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6714)
at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5647)
at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5913)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5752)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:

I just followed all the source code, any suggestions?

Kind regards

Hey,

The form of this code that won't throw the NullPointerException that @alaincheng is talking about requires a change to line 36 and 37;

Instead of
title = (TextView) itemView.findViewById(R.id.text1);
subtitle = (TextView) itemView.findViewById(R.id.text2);

you need to write

title = (TextView) itemView.findViewById(android.R.id.text1);
subtitle = (TextView) itemView.findViewById(android.R.id.text2);

Hope this helps

@andrewm898

Hey,

The form of this code that won't throw the NullPointerException that @alaincheng is talking about requires a change to line 36 and 37;

Instead of
title = (TextView) itemView.findViewById(R.id.text1);
subtitle = (TextView) itemView.findViewById(R.id.text2);

you need to write

title = (TextView) itemView.findViewById(android.R.id.text1);
subtitle = (TextView) itemView.findViewById(android.R.id.text2);

Hope this helps

Good point. I've updated the file now so it should be ok.

By changing this its not working