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Table of contents
1.
Introduction
2.
Working of Volley Library
2.1.
Pre-requisites
3.
Creating a Volley request
3.1.
Request Prioritisation
3.2.
Cancel Requests
4.
Top Features of Volley Library in Android
5.
Top Advantages of Using Volley
6.
Frequently Asked Questions
6.1.
Is volley a REST API?
6.2.
Which is preferable, retrofit or volley?
6.3.
Is volley open source?
6.4.
How is the volley library used?
7.
Conclusion
Last Updated: Mar 27, 2024
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Volley library in Android

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Introduction

Volley is a reliable HTTP (HyperText Transfer Protocol) library that helps in making networking swift and efficient. It was produced by Google; it came into existence during Google I/O 2013 and was announced by Ficus Kirkpatrick.

There was a dire need for a networking class that could work abstractly, without producing any interference in the user experience, in the Android SDK. Earlier, Volley was an integral component of the Android Open Source Project (AOSP). The first instance at which was the Volley Library was by the Play Store team in Play Store Application. Later, in January 2017, Google declared Volley an independent library.
The volley library comes with some superior features like automated and scheduled network requests and numerous concurrent connections; we can prioritize requests in case of conflicts, inhibit or revert specific requests, it allows offer a higher degree of customization, and mainly allows us to manage user interface with higher ease using the asynchronously fetched data from the network.

There is no need to write boilerplate codes using AsyncTask to fetch responses from Web API and display the relevant data in the user interface. Developers can easily skip the tedious process of writing network-based codes using AsyncTask. This reduces the overall size of the source code and makes the repository easy to maintain and debug. This is the main reason that developers prefer Volley over AsyncTask.

Working of Async class

Working of Async class
Image Source: Smashing Magazine

For instance, if we employ Asynctask to fetch an image and its corresponding description from a native JSON array created in server API. The data is fetched and displayed in the user interface, but now if the user rotates the screen and toggles to landscape mode. The previous activity is cleared from the stack, and the data needs to be fetched again. Since multiple network requests are being created for the same data set, it leads to unnecessary congestion at the server and provides a bad user experience due to the latency.

Volley library utilizes the device's cache memory to improve the App performance by reducing the remote server's memory requirement, congestion, and bandwidth. Whenever a recurring data request is made by the user, rather than fetching the data from the server, Volley directly brings it from the cache-saving resource and improves the overall user experience. However, the Volley library is not compatible with large-sized downloads or high quality-streaming operations as it saves all responses in memory while parsing data.

Working of Volley Library

Working of Volley Library
Image Source: Abhi Android

Volley has two default methods that allow us to synchronize pre and post-execute activities, namely the onPreExecute() and onPostExecute() methods. The prerequisites of a network request can be written in the onPreExecute() method, such as fetching the parameters required to make the network request and the post-actions, such as the setting of dialogs, alerts, progress bars, etc. These methods produce distinct and uniform networking codes and eliminate the need for writing BaseTask classes for implementing and managing post operations.

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Working of Volley Library

Pre-requisites

Step 1:

Open build.Gradle(Module: app) and add the following dependency and rebuild the project after syncing of the Gradle:

dependencies{
//…
implementation ‘com.android.volley:volley:1.0.0’
}

Step 2:
In AndroidManifest.xml add the internet permission:

Volley requests can be made by creating two classes in our Android Project:

  • RequestQueue: The network requests are stored in a queue in sequential order. A queue works on the FIFO strategy(First in, first out). So the requests made first are attended to first unless no priority is specified.
  • A Request: Based on our requirements, we must pass the suitable parameters and call the specific API from the web server; we must create valid network requests.

 

A network request can be of various types:

  • StringRequest: To retrieve the response body from the API as a String.
  • JsonArrayRequest: To fetch a JSON Array as a response from the server after the API call.
  • JsonObjectRequest: To send and receive JSON Objects from the server via network requests.
  • ImageRequest: To receive an image from the server as a response.

 

Parameters that should be passed into the constructor to create a network request:

  • First parameter, The Request Method: The method of the created request should be specified, such as GET, POST, PUT, and DELETE.
  • Second parameter URL: String of the URL of the required object.
  • Third parameter ResponseListener: Response Listener, whose callback method contains the response received from the API.
  • Fourth parameter ErrorListener: A Response.ErrorListener, whose callback method will deal with any error generated while executing the network request.

 

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Creating a Volley request

The below shows a Volley string request for fetching a user's name, date of birth, and phone number by sending the username to the server.

private void getdata() {
final List senderList = new ArrayList<>();
StringRequest stringRequest=new StringRequest(com.android.volley.Request.Method.POST, sent, new Response.Listener() {
@Override
public void onResponse(String response) {
try {
JSONArray array = new JSONArray(response);
                //traversing through all the object
                for (int i = 0; i < array.length(); i++)
                {
                    //getting person object from json array
                    JSONObject obj = array.getJSONObject(i);
                    //fetching the details one by one ,through column name
                    String name = obj.getString("Name");
                    String date = obj.getString("Date");
                     String  phone = obj.getString("Phone");
                    senderList.add(new Sender(name,date,phone));
}
//Set the adapter to display the data
startAdapter(senderList);
}
catch (JSONException e)
{
e.printStackTrace();
}
        } 
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
//in case of any error in the path, the error will get displayed as a toast.
Toast.makeText(getActivity(),”Couldn’t fetch data”,Toast.LENGTH_LONG).show();
error.printStackTrace();
}
}
)
{
//a key value data structure is created for sending the parameters
protected Map getParams() throws AuthFailureError {
Mapparams=new HashMap<>();
params.put(“username”,uname);
return params;
}};
//the request is added to the RequestQueue class(MySingleton)
MySingleton.getInstance(getActivity()).addToRequestQueue(stringRequest);
}

Request Prioritisation

We all know that networking is a real-time operation; therefore, at any point in time, the user can make an urgent network request; at this moment, all the network requests in the queue need to be withheld. Volley provides us with extensible methods to set and get the network request priority so that it can be answered without any latency-setPriority() and getpriority ().

Cancel Requests

Volley allows us to cancel the partially executed or non-executed network request using the onStop() method if any already queued network request is not required further. The most efficient way to cancel requests is to add a tag to the request and when the queued requests need to be canceled, call the cancelAll() method. This will cancel all the network requests that possess the corresponding tag.

request.setTag(“TAG”);
requestQueue.cancelAll(“TAG”);

As soon as the cancelAll() method is invoked from the main thread, the residual responses will be dropped instantly.

Top Features of Volley Library in Android

  • Volley allows us to create request queues and assign priorities.
  • We can block and revert unwanted requests.
  • Volley utilizes cache memory to reduce latency while making network requests.
  • It is an abstract class for basic HTTP operations in Android Studio.
  • It reduces space complexity and does auto memory management.
  • It allows a high degree of customization by providing Custom RequestQueue.
  • It allows us to create a RequestQueue for scheduling API calls.
  • It offers a high degree of extensibility to the developers.

Top Advantages of Using Volley

  • Volley libraries possess efficient customization abilities to allow the creation of application-specific requests.
  • The disk and memory caching paradigm followed by Volley is transparent developers understand the data flow.
  • Volley has a bundle of debugging and error-tracing tools that allow easy source code testing and maintenance.
  • Volley covers nearly all the aspects of networking related to Android, including image requests.
  • We can schedule network requests using Volley, such that automated network request is run through the app and the data is updated sequentially at regular interval of time. This feature is used in weather forecasting or stock market management applications to update data daily.
  • Even image requests can be scheduled using the volley library.
  • Volley provides higher security as it can cancel, block or revert a specific request or a block of requests according to the developer commands.

Frequently Asked Questions

Is volley a REST API?

The currently most frequently used libraries to access REST Web APIs are Android Volley and Retrofit.

Which is preferable, retrofit or volley?

Since each library has unique utilities, there is no comparison. Volley is a networking library, and Retrofit allows the creation of simple user interfaces by being a REST client for Android.

Is volley open source?

Yes. It was initially utilized by the team of Play Store before being made available as an open-source library.

How is the volley library used?

A straightforward and quick networking solution for Android apps is the HTTP library called Volley.

Conclusion

This blog discusses an HTTP (HyperText Transfer Protocol) library named volley. If you think this blog has helped you enhance your knowledge of the above question or want to learn more, check out our articles. Visit our website to read more such blogs. 

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