Android Volley - Java

Android Volley is an HTTP library that is used for network operations. It is an open-source library that was introduced by Google to help Android developers handle network requests faster and with less code.

The library offers the following features:

• Easy to use API
• Automatic management of multiple network connections
• Support for custom request types
• Caching of response data
• Support for request prioritization

Developers can use Android Volley to make HTTP requests in their applications, such as fetching data from an API.

Getting started with Android Volley

Integration

To use Android Volley in your project, you need to add the following dependency to your app-level build.gradle file:

dependencies {
    implementation 'com.android.volley:volley:1.2.1'
}

Request types

There are five types of requests that Android Volley supports:

1. StringRequest - Used for plain text HTTP responses.
2. JsonRequest - Used for JSON HTTP responses.
3. ImageRequest - Used for loading images from the network.
4. XmlRequest - Used for XML HTTP responses.
5. FileRequest - Used for downloading files from the network.

Here is an example of how to make a simple GET request using the StringRequest class:

// Instantiate the RequestQueue.
RequestQueue queue = Volley.newRequestQueue(this);
String url = "https://www.example.com";

// Request a string response from the provided URL.
StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
        new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                // Display the response string.
                Log.d(TAG, "Response is: "+ response);
            }
        }, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
        // Display error message.
        Log.e(TAG, "That didn't work! "+ error.getMessage());
    }
});

// Add the request to the RequestQueue.
queue.add(stringRequest);

Request queues

The RequestQueue is responsible for managing a queue of network requests. It handles network request scheduling, caching responses, and delivering responses back to the caller asynchronously.

To create a RequestQueue, use the following code:

RequestQueue queue = Volley.newRequestQueue(this);

Image loading

Android Volley also provides support for loading images from the network. The ImageRequest class is used to fetch and display images in an ImageView.

Here is an example of how to load an image using the ImageRequest class:

// Instantiate the RequestQueue.
RequestQueue queue = Volley.newRequestQueue(this);
String url = "https://www.example.com/image.jpg";

// Request a bitmap response from the provided URL.
ImageRequest imageRequest = new ImageRequest(url,
        new Response.Listener<Bitmap>() {
            @Override
            public void onResponse(Bitmap bitmap) {
                // Display the loaded image in an ImageView.
                imageView.setImageBitmap(bitmap);
            }
        }, 0, 0, ImageView.ScaleType.CENTER_CROP, null,
        new Response.ErrorListener() {
            public void onErrorResponse(VolleyError error) {
                // Display error message.
                Log.e(TAG, "That didn't work! "+ error.getMessage());
            }
        });

// Add the request to the RequestQueue.
queue.add(imageRequest);

Conclusion

Android Volley is a powerful HTTP library that can help developers handle network requests in their Android applications. With its easy-to-use API and support for various request types, developers can easily fetch data from APIs and display it in their app.