使用AsyncTask下载文件的Android应用中的内存泄漏

Question

I am having an issue with an apparent memory leak while using the AsyncTask class. The Android class below is intended to download an image from http and store it into the member variable " Drawable bgImageDrawable ". The function that begins the download process is downloadBackgroundImage() . After this is run, it appears that the Used Memory size increases by 8MB each time. I am downloading a jpeg image file that is 800KB, but I am not sure why the Memory increases significantly. Is there an issue with the code below?

public class Example 
{
    private URL bgImageUrl;
    private Drawable bgImageDrawable;

    public Example(String bg)   {
        try {
            this.setBgImageUrl(new URL(bg));
        } 
        catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }

    public Drawable drawableFromUrl(String url, String srcName) throws java.net.MalformedURLException, java.io.IOException  {
        return Drawable.createFromStream(((java.io.InputStream) new java.net.URL(url).getContent()), srcName);
    }

    public void downloadBackgroundImage()    {
        new DownloadFilesTask().execute(getBgImageUrl().toString());
    }

    public void setBgImageDrawable(Drawable bgImageDrawable) {
        this.bgImageDrawable = bgImageDrawable;
    }

    public URL getBgImageUrl() {
        return bgImageUrl;
    }
    public void setBgImageUrl(URL bgImageUrl) {
        this.bgImageUrl = bgImageUrl;
    }

    /* The purpose of this class is to download a file asynchronously. */
    private class DownloadFilesTask extends AsyncTask<String, Integer, Drawable> 
    {
        protected Drawable doInBackground(String... s)       {
            Drawable bgImage = null;
              try  {
                    bgImage = drawableFromUrl(s[0], "src name");
                    return bgImage;
              } 
              catch (MalformedURLException e)             {
                    e.printStackTrace();
              } 
              catch (IOException e)               {
                    e.printStackTrace();
              }

            return bgImage;
         }

         protected void onProgressUpdate(Integer... progress)        {

         }

         protected void onPostExecute(Drawable result)       {
             setBgImageDrawable(result);
         }
     }
}

Answer 1

You convert 800KB jpeg to a drawable. Your jpeg after downloading decoded to a bitmap. And the bitmap is wraped inside Drawable. So it's ok that decoded bitmap of 800KB jpeg takes 8MB.

You can use profiler to see what exactly taking so much memory. IMHO it's a drawable.

Answer 2

It's cause of longer task

1. Use Activity context only where there is no other choice and NEVER allow a reference to it in something with a scope greater than the scope of the Activity it references.
2. The Android application framework provides many classes designed to make background threading easier for developers. For example, consider using a Service or Synadapter instead of a thread/Asyntask/Loader for performing Long-lived asynchronous background queries in conjunction with the Activity lifecycle.

For this I will suggest you to use the Service or IntentService.