在列表中加载静态图像会减慢滚动速度

Question

My static list consists of images and data.I am loading images in background asynchronously.Still loading of images slows down scrolling performance.If i comment out the image loading code list scrolls very fast.How can i imporove scrolling performance while loading images in list?Below is the code i am using for loading images-

     public View getView(final int i, View v, ViewGroup viewGroup) {
  thumbnailImageView = (ImageView) view.findViewById(R.id.video_thumbnail);
        final String id = video.getId();
        String thumbnailPath = FileUtils.getCachedFileName(0,video.getId());

        BitmapWorkerTask task = new BitmapWorkerTask(thumbnailImageView);

            task2.execute(thumbnailPath);
    .
    .

    }



     class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap>
        {

          private final ImageView imageViewReference;

            public BitmapWorkerTask(ImageView imageView)
            {
              imageViewReference = imageView;
            }





            @Override
            protected Bitmap doInBackground(String... urls) {

                return BitmapFactory.decodeFile(urls[0]);


            }


            @Override
            protected void onPostExecute(Bitmap bitmap)
            {
                imageViewReference.setImageBitmap(bitmap);

            }
        }

Answer 1

You could use Universal Image Library for loading the images in the background. It has a feature to stop loading the image onScroll or Fling.

Answer 2

Try Picasso as it has support for local files as well:

Picasso.with(context).load(R.drawable.landing_screen).into(imageView1);
Picasso.with(context).load("file:///android_asset/DvpvklR.png").into(imageView2);
Picasso.with(context).load(new File(...)).into(imageView3);

Answer 3

Check the below code..It may help to you...You are not providing full code..So I assumed that you are extending your adapter from BaseAdapter and your list item is having one ImageView

final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);

final int cacheSize = maxMemory / 8;

LruCache<Integer, Bitmap> mMemoryCache = new LruCache<Integer, Bitmap>(
        cacheSize) {
    @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR1)
    @Override
    protected int sizeOf(Integer key, Bitmap bitmap) {
        return bitmap.getByteCount() / 1024;
    }
};

/**
 * This will return a bitmap from the cache
 * 
 * @param key
 * @return
 */
public Bitmap getBitmapFromMemCache(Integer key) {
    return mMemoryCache.get(key);
}

/**
 * This method will add the bitmap to the memory cache
 * 
 * @param key
 * @param bitmap
 */
public void addBitmapToMemoryCache(Integer key, Bitmap bitmap) {
    if (getBitmapFromMemCache(key) == null) {
        mMemoryCache.put(key, bitmap);
    }
}

private View video;

@Override
public View getView(int position, View view, ViewGroup parent) {

    ViewHolder holder = null;

    if (view == null) {
        view = LayoutInflater.from(context).inflate(R.layout.list_item,
                null);
        holder = new ViewHolder();
        holder.thumbnailImageView = (ImageView) view
                .findViewById(R.id.video_thumbnail);

        view.setTag(holder);
    }

    else {
        holder = (ViewHolder) view.getTag();
    }


    if (holder.bitmapWorkerTask!= null && holder.bitmapWorkerTask.getStatus() == Status.RUNNING) {
        holder.bitmapWorkerTask.cancel(true);
    }

    Bitmap bitmapFromMemCache = getBitmapFromMemCache(position);
    if (bitmapFromMemCache == null) {
        holder.thumbnailImageView.setImageResource(R.drawable.default_image);
        holder.bitmapWorkerTask = new BitmapWorkerTask(holder.thumbnailImageView,position);
        String thumbnailPath = FileUtils.getCachedFileName(0, video.getId());
        holder.bitmapWorkerTask.execute(thumbnailPath);
    } else {
        holder.thumbnailImageView.setImageBitmap(bitmapFromMemCache);
    }


    ........
}

private class ViewHolder {
    private ImageView thumbnailImageView;
    private BitmapWorkerTask bitmapWorkerTask;
}

class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
    private final ImageView imageViewReference;
    private int position;

    public BitmapWorkerTask(ImageView imageView,int position) {
        imageViewReference = imageView;
        this.position=position;
    }

    @Override
    protected Bitmap doInBackground(String... urls) {
        Bitmap bitmap= BitmapFactory.decodeFile(urls[0]);
        addBitmapToMemoryCache(position, bitmap);
        return bitmap
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        imageViewReference.setImageBitmap(bitmap);
    }
}