Volley Library Fetching JSON Data from URL

In this tutorial, we will fetch the JSON data from the URL using Volley library. Volley is an HTTP Library which provides the facilities for the network connectivity of our app.

The advantages of using the Volley library are as follows:

More comfortable and faster request management.
It provides efficient network management.

Android Volley Fetching JSON Data from URL Example

In this example, we will load the JSON data from the URL using Volley library. The JSON data contains the String "name", String "imageurl" and String "description" of tutorials. After fetching the data from the URL, they are displayed in ListView. You can refer more about JSON parsing tutorial at https://www.javatpoint.com/android-json-parsing-tutorial.

Let's create a JSON data which contains the following information.

JSON data at URL (provide your URL of information) = http://192.168.1.35:8080/jsondata/

{
"tutorials":[
{
"name":"Java",
"imageurl":"https://www.javatpoint.com/images/logo/javahome.png",
"description":"Java is a high level, robust, object-oriented and secure programming language."
},
{
"name":"Android",
"imageurl":"https://www.javatpoint.com/images/logo/androidhome.png",
"description":"Android is a complete set of software for mobile devices."
},
{
"name":"Python",
"imageurl":"https://www.javatpoint.com/images/logo/pythonhome.png",
"description":"Python is a general purpose, dynamic, high level and interpreted programming language."
},
{
"name":"C++",
"imageurl":"https://www.javatpoint.com/cpp/images/cpp-home.png",
"description":"C++ is an object-oriented programming language."
}
]
}

The JSON data looks like as:

Volley Library Fetching JSON Data from URL Create an activity_main.xml in layout and add the following code.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="example.javatpoint.com.volleyreadimagejson.MainActivity">

<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />

<ProgressBar
android:id="@+id/progressBar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:layout_marginBottom="292dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:visibility="gone"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

Now, create a list_item.xml file in the layout directory which contains the row items for ListView. This contains one ImageView for image display and two TextView for text display.

list_item.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="match_parent"
android:padding="16dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<ImageView
android:id="@+id/imageView"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/placeholder"
android:contentDescription="image view" />
<TextView
android:id="@+id/textViewName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="title"
android:textAppearance="@style/Base.TextAppearance.AppCompat.Large" />
</LinearLayout>


<TextView
android:id="@+id/textViewImageUrl"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="url"
android:autoLink="web"
android:textColor="#08308e" />


</LinearLayout>

Create a data model class with name Tutorial.java and information String "name", String "imageurl" and String "description".

Tutorial.java

package example.javatpoint.com.volleyreadimagejson;

public class Tutorial {
String name, imageUrl, description;

public Tutorial(String name, String imageUrl, String description) {
this.name = name;
this.imageUrl = imageUrl;
this.description = description;
}
public String getName() {
return name;
}
public String getImageUrl() {
return imageUrl;
}
public String getDescription() {
return description;
}
}

Create a custom adapter class named as MyAdapter.java and extend ArrayAdapter to handle the custom ListView. In this class we are calling an anonymous class new ImageDownloaderTask(holder.imageView).execute(imageUrl) to download images from URL.

MyAdapter.java

package example.javatpoint.com.volleyreadimagejson;

import android.app.ProgressDialog;
import android.content.Context;
import android.graphics.Bitmap;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;


public class MyAdapter extends ArrayAdapter<Tutorial> {
//the tutorial list that will be displayed
private List<Tutorial> tutorialList;
private Bitmap bitmap;
private Context mCtx;
//here we are getting the tutoriallist and context
//so while creating the object of this adapter class we need to give tutoriallist and context
public MyAdapter(List<Tutorial> tutorialList, Context mCtx) {
super(mCtx, R.layout.list_item, tutorialList);
this.tutorialList = tutorialList;
this.mCtx = mCtx;
}

//this method will return the list item
@Override
public View getView(int position, View convertView, ViewGroup parent) {
//getting the layoutinflater
ViewHolder holder;
LayoutInflater inflater = LayoutInflater.from(mCtx);
convertView = inflater.inflate(R.layout.list_item, null, true);
holder = new ViewHolder();
//getting text views
holder.textViewName = convertView.findViewById(R.id.textViewName);
holder.textDescription = convertView.findViewById(R.id.textViewImageUrl);
holder.imageView = convertView.findViewById(R.id.imageView);

convertView.setTag(holder);
//Getting the tutorial for the specified position
Tutorial tutorial = tutorialList.get(position);
String imageUrl = tutorial.getImageUrl();
String tutorialDescription = tutorial.getDescription();
String tutorialTitle = tutorial.getName();

holder.textViewName.setText(tutorialTitle);
holder.textDescription.setText(tutorialDescription);

if (holder.imageView != null) {
/*-------------fatching image------------*/;
new ImageDownloaderTask(holder.imageView).execute(imageUrl);
}
holder.imageView.setImageBitmap(bitmap);
return convertView;
}
static class ViewHolder {
TextView textViewName;
TextView textDescription;
ImageView imageView;
}
}

Add the following library files in the build.gradle file.

build.gradle

android {
useLibrary 'org.apache.http.legacy'
}

dependencies {
compile 'com.android.volley:volley:1.0.0'
compile 'org.apache.httpcomponents:httpcore:4.4.1'
compile 'org.apache.httpcomponents:httpclient:4.5'
}

Creating an anonymous class ImageDownloaderTask.java which extends AsyncTask<>. This class downloads (or fetch) the images from URL while executing doInbackground() method and returns the result (bitmap) to onPostExecute(). In onPostExecute() method, the bitmap are set to the ImageView.

ImageDownloaderTask.java

package example.javatpoint.com.volleyreadimagejson;

import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.net.HttpURLConnection;
import java.net.URL;
import org.apache.http.HttpStatus;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ImageView;

public class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {

private final WeakReference<ImageView> imageViewReference;
public ImageDownloaderTask(ImageView imageView) {
imageViewReference = new WeakReference<ImageView>(imageView);
}
@Override
protected Bitmap doInBackground(String... params) {
return downloadBitmap(params[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
if (isCancelled()) {
bitmap = null;
}
if (imageViewReference != null) {
ImageView imageView = imageViewReference.get();
if (imageView != null) {
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
} else {
Drawable placeholder = imageView.getContext().getResources().getDrawable(R.drawable.placeholder);
imageView.setImageDrawable(placeholder);
}
}
}
}

private Bitmap downloadBitmap(String imageUrl) {
HttpURLConnection urlConnection = null;
try {
URL uri = new URL(imageUrl);
urlConnection = (HttpURLConnection) uri.openConnection();

int statusCode = urlConnection.getResponseCode();
if (statusCode != HttpStatus.SC_OK) {
return null;
}
InputStream inputStream = urlConnection.getInputStream();
if (inputStream != null) {
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
return bitmap;
}
}
catch (Exception e) {
urlConnection.disconnect();
Log.w("ImageDownloader", "Error downloading image from " + imageUrl);
}
finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
return null;
}
}

In MainActivity.java class, we are fetching and parsing the JSON data from the URL using Volley.

MainActivity.java

package example.javatpoint.com.volleyreadimagejson;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.Toast;
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;
import java.util.List;

public class MainActivity extends AppCompatActivity {

ListView listView;
private static final String JSON_URL = "http://192.168.1.35:8080/jsondata/";
//the tutorial list where we will store all the tutorial objects after parsing json
List<Tutorial> tutorialList;

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

listView = (ListView) findViewById(R.id.listView);
tutorialList = new ArrayList<>();
//this method will fetch and parse the data
loadTutorialList();
}

private void loadTutorialList() {
//getting the progressbar
final ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressBar);
progressBar.setVisibility(View.VISIBLE);

//creating a string request to send request to the url
StringRequest stringRequest = new StringRequest(Request.Method.GET, JSON_URL,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
//hiding the progressbar after completion
progressBar.setVisibility(View.INVISIBLE);


try {
//getting the whole json object from the response
JSONObject obj = new JSONObject(response);

//we have the array named tutorial inside the object
//so here we are getting that json array
JSONArray tutorialsArray = obj.getJSONArray("tutorials");

//now looping through all the elements of the json array
for (int i = 0; i < tutorialsArray.length(); i++) {
//getting the json object of the particular index inside the array
JSONObject tutorialsObject = tutorialsArray.getJSONObject(i);

//creating a tutorial object and giving them the values from json object
Tutorial tutorial = new Tutorial(tutorialsObject.getString("name"), tutorialsObject.getString("imageurl"),tutorialsObject.getString("description"));

//adding the tutorial to tutoriallist
tutorialList.add(tutorial);
}

//creating custom adapter object
MyAdapter adapter = new MyAdapter(tutorialList, getApplicationContext());

//adding the adapter to listview
listView.setAdapter(adapter);

} catch (JSONException e) {
e.printStackTrace();
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
//displaying the error in toast if occur
Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_SHORT).show();
}
});

//creating a request queue
RequestQueue requestQueue = Volley.newRequestQueue(this);

//adding the string request to request queue
requestQueue.add(stringRequest);
}
}

Add the Internet permission in AndroidManifest.xml

AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />

Output:

Volley Library Fetching JSON Data from URL

Android Tutorial

Android Widgets

Activity and Intents

Android Fragments

Android Menu

Android Service

Android AlarmManager

Android Storage

Android SQLite

XML and JSON

Android Multimedia

Android Speech

Android Telephony

Android Device

Camera Tutorial

Sensor Tutorial

Android Graphics

Android Animation

Android Web Service

Google Map

Adding Ads

Android Examples

Android Social

Android Versions

Android Misc

Android MCQ

Android Interview

Android Quiz