Android volley
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Volley is a Google-developed networking library for Android, introduced in 2013, designed to simplify and speed up the networking process for apps. Key features include automatic request scheduling, multiple concurrent connections, response caching, and easy request customization. It facilitates the management of network operations through a request queue that handles request dispatching and response parsing efficiently.
Android volley
- 2. Introduction to Volley. . ● Volley is a networking library developed by Google and introduced during Google I/O 2013. ● The origin of Volley's name: “a burst or emission of many things or a large amount at once”. ● Volley is an HTTP library that makes networking for Android apps easier and most importantly, faster. ● Volley is available through the open AOSP repository.
- 3. Under the hood Architecture and semantics
- 4. Advantages of using volley. . ● Automatic scheduling of network requests. ● Multiple concurrent network connections. ● Transparent disk and memory response caching with standard HTTP cache coherence. ● Support for request prioritization. ● Cancellation request API. You can cancel a single request, or you can set blocks or scopes of requests to cancel. ● Ease of customization, for example, for retry and backoff. ● Strong ordering that makes it easy to correctly populate your UI with data fetched asynchronously from the network. ● Debugging and tracing tools.
- 5. Problems & Solutions- Volley fixed these problems ● All network requests happen serially ● Rotating the screen will reload everything from the network ● AsyncTasks stomp on recycled views ● Compatibility problems on Froyo
- 6. Add Volley to your project The easiest way to add Volley to your project is to clone the Volley repository and set it as a library project: 1. Git clone the repository by typing the following at the command line: 2. Import the downloaded source into your app project as an Android library module.
- 7. Volley library ● Sending a Simple Request ● Setting Up a RequestQueue ● Making a Standard Request ● Implementing a Custom Request
- 8. Sending a Simple Request ● At a high level, you use Volley by creating a RequestQueue and passing it Request objects. ● The RequestQueue manages worker threads for running the network operations, reading from and writing to the cache, and parsing responses. ● Requests do the parsing of raw responses and Volley takes care of dispatching the parsed response back to the main thread for delivery. ● Here I’ll describe, how to add a request to a RequestQueue and cancel a request.
- 9. Adding new requestqueue . ● Volley provides a convenience method Volley.newRequestQueue that sets up a RequestQueue for you, using default values, and starts the queue. ● Sending request - To send a request, you simply construct one and add it to the RequestQueue with add().
- 10. 1. Setting Up a RequestQueue There are explicit steps of creating a RequestQueue, to allow you to supply your own custom behavior. Two different process 1. Set Up a Network and Cache 2. Use a Singleton Pattern
- 11. a. Set Up a Network and Cache A RequestQueue needs two things to do its job: 1. a network to perform transport of the requests 2. a cache to handle caching.
- 12. 1. a network to perform transport of the requests This snippet shows you the steps involved in setting up a RequestQueue:
- 13. 2. a cache to handle caching.
- 14. b. Use a Singleton Pattern Here are some examples of performing RequestQueue operations using the singleton class:
- 15. Making a Standard Request It describes how to use the common request types that Volley supports: 1. StringRequest. Specify a URL and receive a raw string in response. See Setting Up a Request Queue for an example. 2. ImageRequest. Specify a URL and receive an image in response. 3. JsonObjectRequest and JsonArrayRequest (both subclasses of JsonRequest). Specify a URL and get a JSON object or array (respectively) in response.
- 16. Implementing a Custom Request Write a Custom Request For cases where you do need to implement a custom request, this is all you need to do: ● Extend the Request<T> class, where <T> represents the type of parsed response the request expects. So if your parsed response is a string, for example, create your custom request by extending Request<String>. See the Volley toolbox classes StringRequest and ImageRequest for examples of extending Request<T>. ● Implement the abstract methods parseNetworkResponse() and deliverResponse(), described in more detail below.
- 17. 1. parseNetworkResponse A Response encapsulates a parsed response for delivery, for a given type (such as string, image, or JSON). Here is a sample implementation of parseNetworkResponse():
- 18. 2. deliverResponse Volley calls you back on the main thread with the object you returned in parseNetworkResponse(). Most requests invoke a callback interface here, Example given below
- 19. If Any Question ?