CODEWITHSUNDEEP
androidandroid-asynctask
Genadinik
Genadinik

Reputation: 18649

AsyncTask - where is it better to process the code that I get back?

I have a remote call that I make and I am wondering where it is better to put this processing code:

        if ( result == null )
        {       
            Toast.makeText(getApplicationContext(), "Some error message", Toast.LENGTH_LONG).show();                                

        }
        else
        if ( result.equals( "all_problems_db_error" ))
        {
        Log.d( "AllBusinessesActivity" , "result: " + result )                                      
        }
        else
        {
            // Unwrap the stuff from the JSON string                
            String problem_title = null;
            String problem_id = null;

            try
            {
                JSONArray obj = new JSONArray(result);

                if ( obj != null )
                {
                    problems.clear();

                    for ( int i = 0; i < obj.length(); i++ )
                    {
                        JSONObject o = obj.getJSONObject(i);

                        problem_title = o.getString("problem_title");
                        problem_id = o.getString("problem_id");

                        Problem p = new Problem ( );
                        p.setProblemId(problem_id);                         
                        p.setProblemName(problem_title);

                        problems.add( p );
                    }

                    adapter.notifyDataSetChanged();             

                }                                   
            }
            catch ( Exception e )
            {
           // Do something :)
            }               
        }

Is it better to have it in the onPostExecute() or at the end or doInBackground() ?

I now do it in onPostExecute() but every once in a while I experience some slowness, and I have been reading that it might be better to do this in the doInBackground.

Could someone please explain to me the difference? And if I do this in the doInBackground() then what is the purpose of having the onPostExecute method?

Upvotes: 0

Views: 79

Answers (2)

Arun George
Arun George

Reputation: 18592

Is it better to have it in the onPostExecute()

Since in your case there is no manipulation of any UI component, you can have the code in doInBackground(). But since you are showing a toast when the result is null you can check the result in doInBackground() and if the result is not null you can do the remaining processing on that result in the same function or else you can pass on to onPostExecute() where you can show the toast.

at the end or doInBackground() Yes. You can have this code at the end of doInBackground() since this method runs on a non-UI thread and this will definitely reduce the slowness you experience.

The difference between both these method doInBackground() and onPostExecute() is simply that the former runs on a non-UI thread and the later on the UI-Thread.

And if I do this in the doInBackground() then what is the purpose of having the onPostExecute method

Usually the doInBackground() is used to perform time consuming operations. These operations may include activities like calling a webservice or fetching images from servers. In such cases (like fetching images from servers) you want that images to be displayed on your screen (which is your UI). After you fetch these resource you pass on the data to the onPostExecute() where you can update your UI since it runs on your UI thread.

Hope this explanation clears your doubt.

Upvotes: 0

nhaarman
nhaarman

Reputation: 100438

The onPostExecute method is useful when you need to do stuff on the UI Thread. In fact, you cannot do any manipulation of the UI in the doInBackground method.

So try to do all calculations / downloading of data etc. in the doInBackground method, and only the manipulation of your UI in the onPostExecute method.

Upvotes: 2

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