Question

I am using the code of http://android-developers.blogspot.gr/2010/07/multithreading-for-performance.html in combination with http://developer.android.com/training/displaying-bitmaps/index.html code. when i try to download the images from urls asynchronously without change the sample size everything it is ok. But when i try to calculate the sample size nothing appears on the screen(gridview). I read the logcat and i see that all the images are downloaded correctly. the code that i am using for the image download is the next one:

Bitmap downloadBitmap(String url) {

    final HttpClient client = AndroidHttpClient.newInstance("Android");
    final HttpGet getRequest = new HttpGet(url);

    try {
        HttpResponse response = client.execute(getRequest);
        final int statusCode = response.getStatusLine().getStatusCode();
        if (statusCode != HttpStatus.SC_OK) {
            Log.w("ImageDownloader", "Error " + statusCode
                    + " while retrieving bitmap from " + url);
            return null;
        }

        final HttpEntity entity = response.getEntity();
        if (entity != null) {
            InputStream inputStream = null;
            try {
                inputStream = entity.getContent();

                // get Device Screen Dimensions
                DeviceProperties dimensions = new DeviceProperties(activity);

                return 
                decodeBitmapFromResource(url, inputStream,
                        dimensions.getDeviceWidth(),
                        dimensions.getDeviceHeight());
            } finally {
                if (inputStream != null) {
                    inputStream.close();
                }
                entity.consumeContent();
            }
        }
    } catch (IOException e) {
        getRequest.abort();
        Log.w(TAG, "I/O error while retrieving bitmap from " + url, e);
    } catch (IllegalStateException e) {
        getRequest.abort();
        Log.w(TAG, "Incorrect URL: " + url);
    } catch (Exception e) {
        getRequest.abort();
        Log.w(TAG, "Error while retrieving bitmap from " + url, e);
    } finally {
        if ((client instanceof AndroidHttpClient)) {
            ((AndroidHttpClient) client).close();
        }
    }
    return null;
}

and the code i am using for decoding is this:

public static Bitmap decodeBitmapFromResource(String url, InputStream is,
        int reqWidth, int reqHeight) {
    // First decode with inJustDecodeBounds=true to check dimensions
    final BitmapFactory.Options options = new BitmapFactory.Options();

    options.inJustDecodeBounds = true;
    BitmapFactory.decodeStream(new FlushedInputStream(is), null,
            options);
    // Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options , reqWidth,
            reqHeight);

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeStream(new FlushedInputStream(is), null,
            options);
}

the problem appears when i use the both the first and the second BitmapFactory.decodeStream. If i use only the second one everything it is ok but actually i don’t make any sample. Any suggestion? I have lost a lot of time looking for it.

Answer 1

A InputStream can only be read ONCE, then it is gone.

If you want to make a dual pass (one for just the bounds and the second to have the options, you must first copy the input stream to a temporary file (using a FileOutputStream) and then do the dual pass on that file by opening two FileInputStream.