Theory
Networking made manageable
Calling an API from Android by hand is surprisingly fiddly: network calls must run off the main thread (or the app freezes), and their results must come back to the main thread to update the UI. Managing that threading yourself is error-prone.
Volley, Google's HTTP library for Android, handles all of it. You describe a request, what URL, what to do on success or failure, and Volley runs it in the background and calls you back. This lesson introduces Volley and its RequestQueue, so making an API call becomes a few clean lines instead of manual thread juggling.
Theory
The RequestQueue and request types
Volley centres on a RequestQueue: a queue that runs your network requests on background threads and delivers each result back on the main thread. You create the queue once, then add requests to it.
Volley offers request types for different responses: StringRequest for raw text, and JsonObjectRequest / JsonArrayRequest for JSON (which arrive already parsed into a JSONObject or JSONArray). You build a request with its method (GET, POST), URL, a success listener (Response.Listener), and an error listener (Response.ErrorListener), then add it to the queue. Volley does the rest: schedule, run off the UI thread, call you back.
Practical
A Volley request for JSON
val queue = Volley.newRequestQueue(context) // create the RequestQueue once
val request = JsonObjectRequest(
Request.Method.GET, "https://api.example.com/events", null,
{ response -> // success: response is a JSONObject
val events = response.getJSONArray("events")
// parse and show them
},
{ error -> // failure
// show an error message
}
)
queue.add(request) // Volley runs it off the UI thread and calls backFormula
Volley handles the threading for you
The big win is that Volley keeps network work off the main (UI) thread automatically. On Android, doing network calls on the main thread would freeze the interface (and Android forbids it), so the work must run in the background, and Volley manages that, plus scheduling, prioritising, and retries.
Your success and error listeners, though, run on the main thread, so you can safely update the UI in them. So you get correct, non-blocking networking without writing any thread-handling code yourself. Describe the request and the callbacks; Volley runs it properly. That is why libraries like Volley are preferred over hand-rolled networking.
Quiz
What does Volley's RequestQueue do for you?
- It stores the app's data permanently on the device
- It runs network requests on background threads (off the UI thread) and delivers results back via callbacks, handling the threading for you
- It designs the app's layouts
- It replaces the need for an internet connection
Show the answer
It runs network requests on background threads (off the UI thread) and delivers results back via callbacks, handling the threading for you
Volley's RequestQueue runs your network requests on background threads, so they do not block the UI, and delivers the results back through your success/error callbacks (on the main thread), handling the threading and scheduling for you. Option A is wrong: Volley does networking, not permanent local storage (that is a database's job). Option C is wrong: layouts are built in Android's UI tools, not Volley. Option D is wrong: Volley still needs the internet to reach the API; it manages the requests, it does not remove the need for a connection. The benefit is correct, non-blocking networking with minimal code.
Think first
Why not just write the network code by hand instead of using Volley?
You could open a connection and read the response yourself. Why use a library like Volley? Then tap.
Show the answer
Because correct Android networking involves a lot of subtle, repetitive, error-prone work, threading, scheduling, error handling, retries, response parsing, that a library like Volley has already solved well, so writing it by hand wastes effort and invites bugs. Consider what raw networking requires: you must run the request on a BACKGROUND thread (never the UI thread, or the app freezes and Android may kill it), then marshal the result BACK to the main thread to update the UI safely, handle timeouts and connection errors gracefully, possibly retry failed requests, manage multiple concurrent requests without overwhelming the device, and parse the response. Getting all of that right by hand, for every request, is tedious and easy to botch, a misplaced UI update from a background thread, a leaked thread, an unhandled error, and each mistake is a crash or a freeze. Volley packages the correct solution: you simply describe the request (method, URL, listeners) and add it to the queue, and Volley handles the threading, scheduling, prioritisation, and retries, calling your listeners back on the main thread so UI updates are safe. This means less code, fewer bugs, and consistent behaviour, and it lets you focus on WHAT you are fetching, not the plumbing of HOW. This is the general value of good libraries: they encapsulate hard, common problems so you do not re-solve them. For Android networking, Volley (and alternatives like Retrofit) are the professional default for exactly this reason. Reuse a solved solution rather than re-implementing tricky plumbing.
Summary
Key takeaways
- Volley is Google's HTTP library for Android that simplifies network calls.
- It centres on a RequestQueue that runs requests on background threads and delivers results back on the main thread.
- Request types: StringRequest (raw text), JsonObjectRequest and JsonArrayRequest (already-parsed JSON).
- You build a request with a method, URL, a success listener (Response.Listener), and an error listener, then add it to the queue.
- Volley keeps network work off the UI thread automatically (so the app does not freeze) and runs your callbacks on the main thread for safe UI updates.
- Using a library avoids the error-prone manual work of threading, scheduling, retries, and error handling.
- Memory hook: create a RequestQueue, add a request with success/error listeners, Volley runs it off the UI thread and calls you back.