Android RecyclerView Pagination - Next/Previous Pagination

November 15, 2017 Oclemy Android RecyclerView 11 minutes, 41 seconds

In this class we see how to page/paginate data which is very important especially with RecyclerView which are meant to show large datasets.

The type of pagination we do here is the next/previous pagination. The user can navigate pages via the next/previous buttons.

If we reach the last page the next button gets disabled automatically while if we are at the first page the previous button gets disabled. In between both buttons are enabled.

Page 1

Page 2

Let's go.

1. Create Basic Activity Project

  1. First create a new project in android studio. Go to File --> New Project.

  2. Type the application name and choose the company name. New Project Dialog

  3. Choose minimum SDK. Choose minimum SDK

  4. Choose Basic activity. Choose Empty Activity

  5. Click Finish. Finish

Basic activity will have a toolbar and floating action button already added in the layout

Normally two layouts get generated with this option:

No. Name Type Description
1. activity_main.xml XML Layout Will get inflated into MainActivity Layout.Typically contains appbarlayout with toolbar.Also has a floatingactionbutton.
2. content_main.xml XML Layout Will be included into activity_main.xml.You add your views and widgets here.
3. MainActivity.java Class Main Activity.

In this example I used a basic activity.

The activity will automatically be registered in the android_manifest.xml. Android Activities are components and normally need to be registered as an application component.

If you've created yours manually then register it inside the <application>...<application> as following, replacing the MainActivity with your activity name:


        <activity android:name=".MainActivity">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

You can see that one action and category are specified as intent filters. The category makes our MainActivity as launcher activity. Launcher activities get executed first when th android app is run.

Advantage of Creating Basic Activity project

You can optionally choose empty activity over basic activity for this project.

However basic activity has the following advantages:

No. Advantage
1. Provides us a readymade toolbar which gives us actionbar features yet easily customizable
2. Provides us with appbar layout which implements material design appbar concepts.
3. Provides a FloatinActionButton which we can readily use to initiate quick actions especially in examples like these.
4. Decouples our custom content views and widgets from the templating features like toolbar.

Generated Project Structure

AndroidStudio will generate for you a project with default configurations via a set of files and directories.

Here are the most important of them:

No. File Major Responsibility
1. build/ A directory containing resources that have been compiled from the building of application and the classes generated by android tools. Such a tool is the R.java file. R.java file normally holds the references to application resources.
2. libs/ To hold libraries we use in our project.
3. src/main/ To hold the source code of our application.This is the main folder you work with.
4. src/main/java/ Contains our java classes organized as packages.
5. src/main/res/ Contains our project resources folders as follows.
6. src/main/res/drawable/ Contains our drawable resources.
7. src/main/res/layout/ Contains our layout resources.
8. src/main/res/menu/ Contains our menu resources XML code.
9. src/main/res/values/ Contains our values resources XML code.These define sets of name-value pairs and can be strings, styles and colors.
10. AndroidManifest.xml This file gets autogenerated when we create an android project.It will define basic information needed by the android system like application name,package name,permissions,activities,intents etc.
11. build.gradle Gradle Script used to build the android app.

Project Structures

2. Build.gradle

Let's come to our app level(app folder) build.gradle:


dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:24.2.0'
    compile 'com.android.support:design:24.2.0'
    compile 'com.android.support:cardview-v7:24.2.0'

}

3. Create User Interface

User interfaces are typically created in android using XML layouts as opposed to direct java coding.

This is an example of declarative programming.

Advantages of Using XML over Java
No. Advantage
1. Declarative creation of widgets and views allows us to use a declarative language XML which makes is easier.
2. It's easily maintanable as the user interface is decoupled from your Java logic.
3. It's easier to share or download code and safely test them before runtime.
4. You can use XML generated tools to generate XML

Here are our layouts for this project:

(a). activity_main.xml

  • This layout gets inflated to MainActivity user interface.
  • It includes the content_main.xml.

Here are some of the widgets, views and viewgroups that get employed"

No. View/ViewGroup Package Role
1. CordinatorLayout android.support.design.widget Super-powered framelayout that provides our application's top level decoration and is also specifies interactions and behavioros of all it's children.
2. AppBarLayout android.support.design.widget A LinearLayout child that arranges its children vertically and provides material design app bar concepts like scrolling gestures.
3. ToolBar <android.support.v7.widget A ViewGroup that can provide actionbar features yet still be used within application layouts.
4. FloatingActionButton android.support.design.widget An circular imageview floating above the UI that we can use as buttons.
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"
    android:fitsSystemWindows="true"
    tools:context="com.tutorials.hp.recyclerpagination.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        android:src="@android:drawable/ic_dialog_email" />

</android.support.design.widget.CoordinatorLayout>

(b). content_main.xml

This layout gets included in your activity_main.xml. We define our UI widgets here.

In this case we add a RecyclerView and two buttons(next/previous):

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.tutorials.hp.recyclerpagination.MainActivity"
    tools:showIn="@layout/activity_main">

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

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

        <LinearLayout
            android:orientation="horizontal"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content">
            <Button
                android:text="Previous"
                android:id="@+id/prevBtn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
            <Button
                android:text="Next"
                android:id="@+id/nextBtn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
        </LinearLayout>

    </LinearLayout>
</RelativeLayout>

(c). model.xml

This is the layout that defines the model of a single CardView in our RecyclerView:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_margin="5dp"
    card_view:cardCornerRadius="5dp"
    card_view:cardElevation="2dp"
    android:layout_height="130dp">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="Name"
            android:id="@+id/nameTxt"
            android:padding="10dp"
            android:layout_alignParentLeft="true"
             />
    </RelativeLayout>
</android.support.v7.widget.CardView>

Lets now come to classes:

4. MyViewHolder.java

This is our RecyclerView.ViewHolder class:

This class in our RecyclerView.ViewHolder class.

It derives from android.support.v7.widget.RecyclerView.View thus forcing us to create a constructor public MyHolder(View itemView) that takes a View object as a parameter and pass it over the base clas by a call to super(itemView).

Here are the roles of this class

No. Role
1. Hold a View object already inflated from XML layout for recycling. This avoids re-inflation of the same layout which is an expensive process. Thus this improves the performance of list items rendering for recyclerview. The inflated View is received via the constructor
2. Searches for individual widgets by their id from the inflated View and defines instance fields them. This ensures that those widgets can easily be retrieved as instance fields and their values set especially inside our RecyclerView.Adapter sub-class.
3. Can also be used implement onClick event listener which can be handled by other classes especially the adapter class.
package com.tutorials.hp.recyclerpagination.mRecycler;

import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.TextView;

import com.tutorials.hp.recyclerpagination.R;

public class MyViewHolder extends RecyclerView.ViewHolder {

        TextView nametxt;

        public MyViewHolder(View itemView) {
            super(itemView);
            nametxt= (TextView) itemView.findViewById(R.id.nameTxt);
        }
}

4. MyAdapter.java

This is our RecyclerView.Adapter class.

This is our RecyclerView.Adapter class.

It derives from android.support.v7.widget.RecyclerView.Adapter<RecyclerView.ViewHolder myHolder> class.

Deriving from Recylcerview.Adapter will force us to either make our adapter class abstract or go ahead and override a couple of methods. We choose the latter, overriding onCreateViewHolder(ViewGroup parent, int viewType) and onBindViewHolder(MyHolder holder, final int position).

This class will adapt our data set to our RecyclerView which we use an adapterview adapterview.

Here are the main responsibilities of this class:

No. Responsibility
1. This class will be responsible for inflating our custom model layout to a View object to be used as our RecyclerView itemView.
2. A RecyclerView.ViewHolder instance will then be created with the View object passed to it. All these we do inside the onCreateVewHolder() method.
3. We'll then bind data to our view widgets inside the onBindViewHolder().
4. Handling of click events for our inflated View item.
5. Returning the total item Count to be used when rendering our view items.
package com.tutorials.hp.recyclerpagination.mRecycler;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.tutorials.hp.recyclerpagination.R;

import java.util.ArrayList;

public class MyAdapter extends RecyclerView.Adapter<MyViewHolder>  {
    Context c;
    ArrayList<String> spacecrafts;
    public MyAdapter(Context c, ArrayList<String> spacecrafts) {
        this.c = c;
        this.spacecrafts = spacecrafts;
    }

    //INITIALIZE VH
    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v= LayoutInflater.from(parent.getContext()).inflate(R.layout.model,parent,false);
        return new MyViewHolder(v);
    }
    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        //BIND DATA
        holder.nametxt.setText(spacecrafts.get(position));
    }
    //TOTAL NUM
    @Override
    public int getItemCount() {
        return spacecrafts.size();
    }
}

6. Paginator.java

This is the class that will page/paginate our RecyclerView data.

package com.tutorials.hp.recyclerpagination.mPager;

import java.util.ArrayList;

public class Paginator {
    public static final int TOTAL_NUM_ITEMS=52;
    public static final int ITEMS_PER_PAGE=7;
    public static final int ITEMS_REMAINING=TOTAL_NUM_ITEMS % ITEMS_PER_PAGE;
    public static final int LAST_PAGE=TOTAL_NUM_ITEMS/ITEMS_PER_PAGE;

    public ArrayList<String> generatePage(int currentPage)
    {
        int startItem=currentPage*ITEMS_PER_PAGE+1;
        int numOfData=ITEMS_PER_PAGE;
        ArrayList<String> pageData=new ArrayList<>();

        if (currentPage==LAST_PAGE && ITEMS_REMAINING>0)
        {
            for (int i=startItem;i<startItem+ITEMS_REMAINING;i++)
            {
                pageData.add("Number "+i);
            }
        }else
        {
            for (int i=startItem;i<startItem+numOfData;i++)
            {
                pageData.add("Number "+i);
            }
        }
        return pageData;
    }
}

7. MainActivity.java

So this is our main activity. It derives from AppCompatActivity.

Here are it's major responsibilities:

No. Responsibility
1. Allow itself to become an android activity component by deriving from android.app.activity.
2. Listen to activity creation callbacks by overrding the onCreate() method.
3. Invoke the onCreate() method of the parent Activity class and tell it of a Bundle we've received.
4. Inflate the activity_main.xml into a View object and set it as the content view of this activity.
package com.tutorials.hp.recyclerpagination;

import android.os.Bundle;
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 android.widget.Button;

import com.tutorials.hp.recyclerpagination.mPager.Paginator;
import com.tutorials.hp.recyclerpagination.mRecycler.MyAdapter;

public class MainActivity extends AppCompatActivity {

    RecyclerView rv;
    Button nextBtn, prevBtn;
    Paginator p = new Paginator();
    private int totalPages = Paginator.TOTAL_NUM_ITEMS / Paginator.ITEMS_PER_PAGE;
    private int currentPage = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        //RFERENCE VIEWS
        rv = (RecyclerView) findViewById(R.id.rv);
        nextBtn = (Button) findViewById(R.id.nextBtn);
        prevBtn = (Button) findViewById(R.id.prevBtn);
        prevBtn.setEnabled(false);

        //RECYCLER PROPERTIES
        rv.setLayoutManager(new LinearLayoutManager(this));

        //ADAPTER
        rv.setAdapter(new MyAdapter(MainActivity.this, p.generatePage(currentPage)));

        //NAVIGATE
        nextBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                currentPage += 1;
                // enableDisableButtons();
                rv.setAdapter(new MyAdapter(MainActivity.this, p.generatePage(currentPage)));
                toggleButtons();

            }
        });
        prevBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                currentPage -= 1;

                rv.setAdapter(new MyAdapter(MainActivity.this, p.generatePage(currentPage)));

                toggleButtons();
            }
        });
    }

    private void toggleButtons() {
        if (currentPage == totalPages) {
            nextBtn.setEnabled(false);
            prevBtn.setEnabled(true);
        } else if (currentPage == 0) {
            prevBtn.setEnabled(false);
            nextBtn.setEnabled(true);
        } else if (currentPage >= 1 && currentPage <= totalPages) {
            nextBtn.setEnabled(true);
            prevBtn.setEnabled(true);
        }
    }
}

More Resources

Resource Link
GitHub Browse Browse
GitHub Download Link Download

Best Regards, Oclemy.

Comments