Implementation of Number Pager Adapter with shell LruCache for caching of imgae. #Currently only memory caching is implemented Things to do : #Add file cache

LruCache in a ViewPager

public class NumberPagerAdapter extends PagerAdapter {

    View v;

    private LayoutInflater inflater;

    private Context contxt;

    private LruCache<String, Bitmap> mMemoryCache;

    final static int ALPHAS_TO_LEARN = 26;

   

    public NumberPagerAdapter(Context context) {

        this.contxt = context;
        inflater = LayoutInflater.from(context);

        setCache();
    }

    private void setCache() {
        // TODO Auto-generated method stub
        // Get max available VM memory, exceeding this amount will throw an
        // OutOfMemory exception. Stored in kilobytes as LruCache takes an
        // int in its constructor.
        final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
        // Use 1/8th of the available memory for this memory cache.
        final int cacheSize = maxMemory / 10;

        mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {
            @SuppressLint("NewApi")
            @Override
            protected int sizeOf(String key, Bitmap bitmap) {
                // The cache size will be measured in kilobytes rather than
                // number of items.
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB_MR1) {
                    return bitmap.getRowBytes() * bitmap.getHeight() / 1024;
                } else {
                    return bitmap.getByteCount() / 1024;
                }

            }
        };

    }

    public void addBitmapToMemoryCache(String key, Bitmap bitmap) {
        if (getBitmapFromMemCache(key) == null) {
            mMemoryCache.put(key, bitmap);
        }
    }

    public Bitmap getBitmapFromMemCache(String key) {
        return mMemoryCache.get(key);
    }

    public void loadBitmap(int resId, ImageView mImageView) {
        final String imageKey = String.valueOf(resId);

        final Bitmap bitmap = getBitmapFromMemCache(imageKey);
        if (bitmap != null) {
            mImageView.setImageBitmap(bitmap);
        } else {
            mImageView.setImageResource(R.drawable.ic_launcher);
            BitmapWorkerTask task = new BitmapWorkerTask(mImageView);
            task.execute(resId);
        }
    }

    class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {
        ImageView v;

         // Decode image in background.
        public BitmapWorkerTask(ImageView mImageView) {
            // TODO Auto-generated constructor stub
            v = mImageView;
        }

        @Override
        protected Bitmap doInBackground(Integer... params) {
            //Define your own width and height
          final Bitmap bitmap = decodeSampledBitmapFromResource( contxt.getResources(), params[0], 100, 100);
            //final Bitmap bitmap = decodeSampledBitmapFromResource(contxt.getResources(), params[0], width, height);
            addBitmapToMemoryCache(String.valueOf(params[0]), bitmap);
            return bitmap;
        }

        @Override
        protected void onPostExecute(Bitmap result) {
            // TODO Auto-generated method stub
            v.setImageBitmap(result);
        }

    }

    public Object instantiateItem(View collection, int position) {

        v = inflater.inflate(R.layout.alpha_bet, null);

        initViews(v, position);

        // pos = position;

        ((ViewPager) collection).addView(v, 0);
        return v;
    }

    /**
     * method that initializes and set views
     */
    private void initViews(View v, int position) {
     //your Resource Id and ImageView
     loadBitmap( resId,  mImageView)
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return ALPHAS_TO_LEARN;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        // TODO Auto-generated method stub
        return view.equals((LinearLayout) object);
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object view) {

        ((ViewPager) container).removeView((LinearLayout) view);
        System.gc();

    }

    public Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight) {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(res, resId, options);

        options.inPurgeable = true;
        options.inInputShareable = true;
        // Calculate inSampleSize Reduces Quality Use if You can sacrifice Quality
        // options.inSampleSize=2;
        // Removed quality issues

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeResource(res, resId, options);
    }

}