Invoking services asynchronously in android without an explicit try catch

[8年前 に Denis Signoretto によって更新されました。]

Hi,

I'm not an expert of Android programming and I'm writing some code using Mobile SDK for Android (sorry if I'll write something wrong).

In Android when I need to invoke services asynchronously (like documentation suggests at the moment I'm writing)
I had to write my own callback or use an existing one and invoke the service creating first a session and specifing a callback.
When I invoke the service method I must surround it with a try catch block because its signature being the same of sync case and it correcly throws an Exception.

AsyncTaskCallback callback = new JSONArrayAsyncTaskCallback() {

    public void onFailure(Exception exception) {
        // Implement exception handling code
    }

    public void onSuccess(JSONArray result) {
        // Called after request has finished successfully
    }

};

UserService userService = new UserService(session);
session.setCallback(callback);
try {
    service.getGroupEntries(10184, 0, 0, -1, -1);
catch (Exception e) { ... }

In async call the exception is already managed by onFailure() method. Can make sense overload service methods with the possibility to invoke a service passing the callback, returning void and without throwing exception? E.g.

UserService userService = new UserService(session, callback);
service.getGroupEntries(10184, 0, 0, -1, -1);

Is there an already existing way getting shorter code ?
(Am I misleading and there is a good reason to keep an explicit try catch block) ?

Thanks,
Denis.

[8年前 に Javier Gamarra によって更新されました。]

The exception is also thrown if something fails when creating the JSON Object to do the request (like a parameter being null when it shouldn't) but yeah, the main reason there is an exception is because the generated method and we can't assume there is a callback present for the sync case.

We'll try to simplify the code, I don't know if presenting two methods with different signatures would confuse the user... I'll discuss it with Bruno Farache and let you know

[8年前 に Bruno Farache によって更新されました。]

Yes, it's because the same service method can be used by both async and sync calls. For async calls, something wrong can happen even before sending the request (like Javier said, if the JSON is malformed, or if session.invoke(_command) throws something too).

If you still have the callback reference you can just call onFailure directly:

catch (Exception e) {
callback.onFailure(e);
}

[8年前 に Bruno Farache によって更新されました。]

A good solution would be for the generated methods to return a Call object instead, and the user would decide if that call is async or sync, like this:

Call<JSONArray> call = service.getUserSites();

// Sync

try {
JSONArray sites = call.execute();
}
catch (Exception e) {}

// Async

call.async(new JSONArrayCallback() { ... });

This would break all our APIs though. Maybe it's a good idea to do it now since we are about to release 2.0.

[8年前 に Denis Signoretto によって更新されました。]

+1

Great!