Android Volley与AsyncTask的使用关系及App生命周期下HTTP请求处理的技术咨询

Let's break down each of your Volley-related questions one by one—these are all really common pain points when working with network requests on Android, so great to ask upfront!

1. Does Volley keep processing a request if the app is closed mid-request? #

It depends on whether your app's process is still alive:

• If the user just swipes the app to the background (but the system hasn't killed the process yet), Volley will continue processing the request until it receives a response or times out.
• If the app is fully closed (either force-stopped by the user or terminated by the system to free resources), Volley's threads get shut down immediately. The request might have already reached your server (and the server could still process it), but your app will never receive the response callback.

2. Can I check if a previous request was sent after restarting the app? #

Volley doesn't persist request history by default—so out of the box, you can't look up past requests. If you need this capability, you'll have to build your own persistence layer:

• Save critical request details (like request ID, endpoint, payload, timestamp) to a local database or SharedPreferences right before sending the request.
• After restarting the app, you can check this local storage. For extra certainty, you could also add a server endpoint to verify if the request was processed successfully.

3. What happens to the request's response if the app is closed? #

If your app's process is terminated before the response comes back, Volley's callback methods (onResponse() or onErrorResponse()) will never run—there's no active app context to handle the response. If the app is just in the background (process still alive), the callback will fire normally once the response is received.

4. Can I capture the response and update the local database? #

Absolutely—but only if the app is still running (either foreground or background with an active process). In your Volley request's onResponse() callback, you can run your database update logic (just make sure to do database operations on a background thread—don't block the main thread!).

If the app closes before the response arrives, you won't get the callback, so you can't trigger the database update. For cases where you need to guarantee the database gets updated even if the app closes, combine Volley with a persistent background task tool like WorkManager, which can re-schedule the task and handle the update once conditions are right.

5. What's a reasonable design pattern for these types of HTTP requests? #

It all comes down to how critical the request is:

• Non-critical requests (e.g., analytics logs, user activity tracking): Use Volley with default settings. If the request fails because the app closes, it's usually not a big deal—you can add optional retry logic for transient network errors if needed.
• Critical requests (e.g., submitting a payment, saving user data):
  1. Persist the request details to a local database before sending it (databases are better than SharedPreferences for complex payloads).
  2. Mark the request as "pending" in local storage.
  3. Send the request via Volley.
  4. On successful response, mark the request as "completed" in local storage and run any necessary local updates (like database changes).
  5. On failure, either retry immediately (for network errors) or flag it to retry when the app restarts.
• For all requests, make sure to handle network errors gracefully (timeouts, no connectivity) and inform the user if the action affects their experience.

6. Can I use Volley with background tasks to send requests when the app isn't running? #

Yes! The best way to do this is with WorkManager (part of Android Jetpack):

• Create a Worker subclass, and in its doWork() method, initialize a Volley RequestQueue and send your request.
• Schedule the work using WorkManager's constraints (e.g., only run when there's network connectivity, or when the device is charging).
• WorkManager adheres to Android's background execution rules (especially important for Android 8.0+ where background services are restricted), so your request will be sent at an appropriate time even if the app isn't running.

内容的提问来源于stack exchange，提问作者Kraken