android AsyncTask with activity lifecycle

Question

Am using AsyncTask in order to download images within my activity

the flow goes like this:

protected void onPreExecute() {
        \\begin animation
}

protected IUpiResponse doInBackground(String... params) {
         \\ download the image
}

protected void onPostExecute(IUpiResponse upiResponse) {
         \\stop the animation
}

till here everything fine, the problem start if i go to background while the asynctask is working sometimes I get an exception nullpointer in the animation stops, because the views no longer valid (i guess),

I can check before the stop animation if the activity is in foreground but i prefer to avoid this approach, what else i can do ?

Terwilliger

Did you try it surrund with try {} catch{} ? – Meghanmeghann

i agree i can catch this exception, but i prefer to avoid this kind of trick – Terwilliger

are you switching to another activity when you come into the onPostExecute()?? – Photocathode

In that case catch the exception and make print it so you know what is the issue, there you can see what you can make. – Meghanmeghann

To little information to give an answer, but keep in mind that an AsyncTask does not run on UI thread, therefore you cannot access/update Views directly from the doInBackground(). – Intubate

Narendra pal: am not switching any activity AndyRes: am doing update from the pre and post Execute not in doinBackground – Terwilliger

testing if the view is still visible before stopping an animation on it sound perfectly reasonable to me – Etherealize

Answer 1

I prefer to avoid the asyncTask approach and to download the images in a simple thread, which also saves them to persistence layer such as file system, and then sends an Intent ,

Note: if the activity in the background the Intent ( if you register and unregister your receiver in onResume and onPause as advised ) will not be received so to avoid such cases inside onResume you can check if there is update waiting for you

Judicative

This is super cheat / workaround / fake solution.. ;( – Farmhouse