Hi,

I am new to Android programming. I would like to know if it is better to
have seperate AsyncTasks for every screen on your application or is it
better to have one AsynTask class that handles all processing from
different screens on my application ?

I have looked at stackoverflow but its still not clear to me. I'm thinking
one class might be a lot of overhead and making seperate AsyncTasks for
every screen of my application will be good for performance.

Thanks for any advice.
Albertus

On Tue, Nov 13, 2012 at 3:44 AM, Albertus Kruger
<albertus.kru...@gmail.com>wrote:

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TreKing <http://sites.google.com/site/rezmobileapps/treking> - Chicago
transit tracking app for Android-powered devices

Hi All,

Have a separate Async task class which serves the HTTP Request to all of
your Activities and let your Activities implments a listener which helps
the AsycnTask class to get the data from "onpostexecutes" method.

here is an example which i have written in a blog.

http://www.androidsnippets.com/asyntask-in-android

Mukesh

Create a separate AsyncTask subclass for each different task that needs to
be done.

It is bad Java design to create one large AsyncTask subclass that handles
everything in your app. That would mean you'd have to create a large
'doInBackground' method (being able to handle all cases), possibly create a
large 'onPostExecute' as well, etc, and riddle your code with 'if'
statements or large 'switch' statements.

In the end, all your AsyncTask instances/objects, regardless which subclass
they actually are, are run on one 'global' system queue and 'global' pool
of threads. They all share it.

For executing a particular AsyncTask instance/object: You can execute an
AsyncTask instance/object only once (i.e. call 'execute' on the object only
once).

--- Anton.

I see several people have already replied, and correctly explained that
having just one AsyncTask is a bad idea. But none seem to have commented:
the very question, posed as a choice between one AsyncTask vs. one for each
screen, seems to imply a fundamental misunderstanding of the purpose of
AyncTask.

The purpose of AyncTask is not to handle something for every screen. It is
to handle long tasks that do not belong in the UI thread in the first
place, the prototypical example being the upload or download of a single
file via HTTP, with occasional, light communication back to the UI thread,
e.g. progress updates on that up/download.

AsyncTask is not a general purpose multi-tasking tool. As has already been
pointed out, you can call the executor only once, and then not again. So it
is not good for a background task that sits and waits for messages,
processing each in turn. Looper/Handler is more suitable for that.
AsyncTask is more useful for "one shot" tasks, and specifically for those
that take too long to allow in the UI thread.

Even for these tasks, complications emerge when you use AsyncTask and the
phone is rotated.
See https://groups.google.com/forum/?fromgroups=#!topic/android-developer...
for several different ways of dealing with this complication, choose the
one best for your own application.