Question

I have a handler used to display images in a specified interval loop, on reaching the last image, it goes back to the first image which is the correct. However, i’m having problems with it as it’s causing some devices to crash and makes the CPU usage go up significantly, i’m just wondering what is wrong with the code?

I instantiate it like the following at the top of the fragment:

final public static Handler handler = new Handler();
boolean isRunning = false;

Then in the onPostExecute part of an AsyncTask, I have this code:

 @Override
         protected void onPostExecute(Void v) {

            if(!isRunning) {
             Runnable runnable = new Runnable() {

                @Override
                public void run() {



                    anImageView.setVisibility(View.VISIBLE);
                    isRunning = true;
                    counter++;

                    //imageDownloader.download(data.get(i).getImageURL(), anmageView);
                    if(TabsViewPagerFragmentActivity.theImages !=null && TabsViewPagerFragmentActivity.theImages.size() > 0){
                    Bitmap anImage = TabsViewPagerFragmentActivity.theImages.get(i);
                    anImageView.setImageBitmap(anImage);
                    }

                    i++;
                    if(i>TabsViewPagerFragmentActivity.theImages.size()-1)
                    {
                    i=0;    
                    }



                    handler.postDelayed(this, 1500); 
                }




             };
             handler.postDelayed(runnable, 0);




          }  

         }

The above AsyncTask is called within the onCreate() method.
Secondly, I have a refresh button which re-downloads these images in order to get the latest ones as they change periodically. Therefore I have an onClick() event attached to the refresh button. This also works fine but here is the code which is called:

@Override
     protected void onPostExecute(Void v) {

         for(int i=0;i<data.size()-1;i++) {

            Bitmap anImage = getBitmapFromURL(data.get(i).getImageURL());
            theImagesRefreshed.add(anImage);

         }



         if(!isRunning) {
             Runnable runnable = new Runnable() {

                @Override
                public void run() {



                    anImageView.setVisibility(View.VISIBLE);
                    isRunning = true;
                    counter++;

                    //imageDownloader.download(data.get(i).getImageURL(), anImageView);
                    if(theImagesRefreshed !=null && theImagesRefreshed.size() > 0){
                    Bitmap anImage = theImagesRefreshed.get(i);
                    anImageView.setImageBitmap(anImage);
                    }

                    i++;
                    if(i>theImagesRefreshed.size()-1)
                    {
                    i=0;    
                    }



                    handler.postDelayed(this, 1500); 
                }




             };
             handler.postDelayed(runnable, 0);


         }


     }

I think that the handler is not setup right and is causing the performance issues. Can anyone see anything wrong with this code?

Thanks in advance!

Answer 1

You need to call Looper.prepare() while using handlers in threads .So write Looper.prepare() after you are creating instance of Runnable