Question

I would like my app to clear image cache on exit. I cant figure out how do i call my clearcache() from my image loader activity. I’m getting an error “No enclosing instance of the type MainGridViewImageLoader is accessible in scope“. Could somebody please guide me how it is done? Below are my codes, i’ve marked those areas with comments.

MainPageActivity.class

@Override
        public void onBackPressed() {
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setMessage("Do you want to exit?")
                   .setCancelable(false)
                   .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                       public void onClick(DialogInterface dialog, int id) {

                           Intent intent = new Intent(Intent.ACTION_MAIN);
                           intent.addCategory(Intent.CATEGORY_HOME);
                           intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                           startActivity(intent);

                           MainGridViewImageLoader.this.clearCache(); //<<"No enclosing instance of the type MainGridViewImageLoader is accessible in scope"
                               System.exit(0);
                       }
                   })
                   .setNegativeButton("No", new DialogInterface.OnClickListener() {
                       public void onClick(DialogInterface dialog, int id) {
                            dialog.cancel();
                       }
                   });
            AlertDialog alert = builder.create();
            alert.show();

    }

MainGridViewImageLoader.class

public class MainGridViewImageLoader {

    MemoryCache memoryCache=new MemoryCache();
    FileCache fileCache;
    private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
    ExecutorService executorService; 

    public MainGridViewImageLoader(Context context){
        fileCache=new FileCache(context);
        executorService=Executors.newFixedThreadPool(5);
    }

   final int stub_id = R.drawable.no_image;
    public void DisplayImage(String url, ImageView imageView)
    {
        imageViews.put(imageView, url);
        Bitmap bitmap=memoryCache.get(url);
        if(bitmap!=null)
            imageView.setImageBitmap(bitmap);
        else
        {
            queuePhoto(url, imageView);
            imageView.setImageResource(stub_id);

        }
    }

    private void queuePhoto(String url, ImageView imageView)
    {
        PhotoToLoad p=new PhotoToLoad(url, imageView);
        executorService.submit(new PhotosLoader(p));
    }

    private Bitmap getBitmap(String url) 
    {
        File f=fileCache.getFile(url);

        //from SD cache
        Bitmap b = decodeFile(f);
        if(b!=null)
            return b;

        //from web
        try {
            Bitmap bitmap=null;
            URL imageUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setInstanceFollowRedirects(true);
            InputStream is=conn.getInputStream();
            OutputStream os = new FileOutputStream(f);
            Utils.CopyStream(is, os);
            os.close();
            bitmap = decodeFile(f);
            return bitmap;
        } catch (Exception ex){
           ex.printStackTrace();
           return null;
        }
    }

    //decodes image and scales it to reduce memory consumption
    private Bitmap decodeFile(File f){
        try {
            //decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f),null,o);

            //Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE=70;
            int width_tmp=o.outWidth, height_tmp=o.outHeight;
            int scale=1;
            while(true){
                if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                    break;
                width_tmp/=2;
                height_tmp/=2;
                scale*=2;
            }

            //decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize=scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {}
        return null;
    }

    //Task for the queue
    private class PhotoToLoad
    {
        public String url;
        public ImageView imageView;
        public PhotoToLoad(String u, ImageView i){
            url=u; 
            imageView=i;
        }
    }

    class PhotosLoader implements Runnable {
        PhotoToLoad photoToLoad;
        PhotosLoader(PhotoToLoad photoToLoad){
            this.photoToLoad=photoToLoad;
        }

        @Override
        public void run() {
            if(imageViewReused(photoToLoad))
                return;
            Bitmap bmp=getBitmap(photoToLoad.url);
            memoryCache.put(photoToLoad.url, bmp);
            if(imageViewReused(photoToLoad))
                return;
            BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
            Activity a=(Activity)photoToLoad.imageView.getContext();
            a.runOnUiThread(bd);
        }
    }

    boolean imageViewReused(PhotoToLoad photoToLoad){
        String tag=imageViews.get(photoToLoad.imageView);
        if(tag==null || !tag.equals(photoToLoad.url))
            return true;
        return false;
    }

    //Used to display bitmap in the UI thread
    class BitmapDisplayer implements Runnable
    {
        Bitmap bitmap;
        PhotoToLoad photoToLoad;
        public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
        public void run()
        {
            if(imageViewReused(photoToLoad))
                return;

            if(bitmap!=null)
                photoToLoad.imageView.setImageBitmap(bitmap);
          else
              photoToLoad.imageView.setImageResource(stub_id);

        }
    }

    public void clearCache() {
        memoryCache.clear();
        fileCache.clear();
    }



}

Answer 1

Will the below codes clear my image memory cache?

public void clearApplicationData() 
         {
             File cache = getCacheDir();
             File appDir = new File(cache.getParent());
             if (appDir.exists()) {
                 String[] children = appDir.list();
                 for (String s : children) {
                     if (!s.equals("lib")) {
                         deleteDir(new File(appDir, s));Log.i("TAG", "**************** File /data/data/APP_PACKAGE/" + s + " DELETED *******************");
                     }
                 }
             }
         }

         public static boolean deleteDir(File dir) 
         {
             if (dir != null && dir.isDirectory()) {
                 String[] children = dir.list();
                 for (int i = 0; i < children.length; i++) {
                     boolean success = deleteDir(new File(dir, children[i]));
                     if (!success) {
                         return false;
                     }
                 }
             }
             return dir.delete();
         }