How to load images from a URL txt doc, in Async Task?

Question

I have images loading from a website txt doc. the text document holds the URL for the images.

I dont want this to block the main UI as it does wating for the images to load from the text doxument.

Would i would like to do is load the URL in a AsyncTask in the background or something. and then the image URLs are stored in variables and sent over to my Lazy Downloader i will create.

Can some one please give me an example of how to actually put the part where i want to load the image URL from a website text doc (http://www.example.com/sites/images.txt) i know how to load the text from the file, just dont know how to do it in a AsyncTask.

An example would be greatly appreciated!

  public void getImages() throws IOException{

    DefaultHttpClient httpclient = new DefaultHttpClient();

    HttpGet httppost = new HttpGet("https://sites.google.com/site/theitrangers/images/webImages.txt");
    HttpResponse response;

        response = httpclient.execute(httppost);


            HttpEntity ht = response.getEntity();

            BufferedHttpEntity buf = new BufferedHttpEntity(ht);

            InputStream is = buf.getContent();


            BufferedReader r = new BufferedReader(new InputStreamReader(is));

            StringBuilder total = new StringBuilder();
            String line;
            while ((line = r.readLine()) != null) {
                total.append(line + "\n");

              imageUrl = total.toString();
            }

            }
            public void getImage2() throws IOException{

                DefaultHttpClient httpclient = new DefaultHttpClient();

                HttpGet httppost = new HttpGet("https://sites.google.com/site/theitrangers/images/webImage2.txt");
                HttpResponse response;

                    response = httpclient.execute(httppost);


                        HttpEntity ht = response.getEntity();

                        BufferedHttpEntity buf = new BufferedHttpEntity(ht);

                        InputStream is = buf.getContent();


                        BufferedReader r = new BufferedReader(new InputStreamReader(is));

                        StringBuilder total = new StringBuilder();
                        String line;
                        while ((line = r.readLine()) != null) {
                            total.append(line + "\n");

                          imageUrl2 = total.toString();

                        }

}
            public class ImageAdapter extends BaseAdapter {
                /** The parent context */
                private Context myContext;public ImageAdapter() {
                    // TODO Auto-generated constructor stub
                }
                /** URL-Strings to some remote images. */

                private String[] myRemoteImages = {imageUrl,imageUrl2};






                /** Simple Constructor saving the 'parent' context. */
                public ImageAdapter(Context c) { this.myContext = c; }

                /** Returns the amount of images we have defined. */
                public int getCount() { return this.myRemoteImages.length; }

                /* Use the array-Positions as unique IDs */
                public Object getItem(int position) { return position; }
                public long getItemId(int position) { return position; }

                /** Returns a new ImageView to
                * be displayed, depending on
                * the position passed. */
                public View getView(int position, View convertView, ViewGroup parent) {
                ImageView i = new ImageView(this.myContext);

                try {
                                /* Open a new URL and get the InputStream to load data from it. */
                                URL aURL = new URL(myRemoteImages[position]);
                                URLConnection conn = aURL.openConnection();
                                conn.connect();
                                InputStream is = conn.getInputStream();  
                                /* Buffered is always good for a performance plus. */
                                BufferedInputStream bis = new BufferedInputStream(is);
                                /* Decode url-data to a bitmap. */
                                Bitmap bm = BitmapFactory.decodeStream(bis);
                                bis.close();
                                is.close();

                                /* Apply the Bitmap to the ImageView that will be returned. */
                                i.setImageBitmap(bm);
                        } catch (IOException e) {

                                Log.e("DEBUGTAG", "Remtoe Image Exception", e);
                        }

                /* Image should be scaled as width/height are set. */
                i.setScaleType(ImageView.ScaleType.FIT_CENTER);
                /* Set the Width/Height of the ImageView. */
                i.setLayoutParams(new Gallery.LayoutParams(150, 150));
                return i;
                }

                /** Returns the size (0.0f to 1.0f) of the views
                * depending on the 'offset' to the center. */
                public float getScale(boolean focused, int offset) {
                /* Formula: 1 / (2 ^ offset) */
                return Math.max(0, 1.0f / (float)Math.pow(2, Math.abs(offset)));
                }
                }
            public class ImageAdapter2 extends BaseAdapter {
                /** The parent context */
                private Context myContext;public ImageAdapter2() {
                    // TODO Auto-generated constructor stub
                }
                /** URL-Strings to some remote images. */

                private String[] myRemoteImages = {imageUrl2};






                /** Simple Constructor saving the 'parent' context. */
                public ImageAdapter2(Context c) { this.myContext = c; }

                /** Returns the amount of images we have defined. */
                public int getCount() { return this.myRemoteImages.length; }

                /* Use the array-Positions as unique IDs */
                public Object getItem(int position) { return position; }
                public long getItemId(int position) { return position; }

                /** Returns a new ImageView to
                * be displayed, depending on
                * the position passed. */
                public View getView(int position, View convertView, ViewGroup parent) {
                ImageView i = new ImageView(this.myContext);

                try {
                                /* Open a new URL and get the InputStream to load data from it. */
                                URL aURL = new URL(myRemoteImages[position]);
                                URLConnection conn = aURL.openConnection();
                                conn.connect();
                                InputStream is = conn.getInputStream();  
                                /* Buffered is always good for a performance plus. */
                                BufferedInputStream bis = new BufferedInputStream(is);
                                /* Decode url-data to a bitmap. */
                                Bitmap bm = BitmapFactory.decodeStream(bis);
                                bis.close();
                                is.close();

                                /* Apply the Bitmap to the ImageView that will be returned. */
                                i.setImageBitmap(bm);
                        } catch (IOException e) {

                                Log.e("DEBUGTAG", "Remtoe Image Exception", e);
                        }

                /* Image should be scaled as width/height are set. */
                i.setScaleType(ImageView.ScaleType.FIT_CENTER);
                /* Set the Width/Height of the ImageView. */
                i.setLayoutParams(new Gallery.LayoutParams(150, 150));
                return i;
                }

                /** Returns the size (0.0f to 1.0f) of the views
                * depending on the 'offset' to the center. */
                public float getScale(boolean focused, int offset) {
                /* Formula: 1 / (2 ^ offset) */
                return Math.max(0, 1.0f / (float)Math.pow(2, Math.abs(offset)));




                }
}

}

Answer 1

Do the fetching of the txt file in onPreExecute() method in your AsyncTask. But before you do this, create progress dialog and set it .setCancelable(false). In doInBackground(), do the fetching the images...and in onPostExecute() do some UI stuff, like displaying of the images.

Edit:

protected class Somename extends AsyncTask<String, String, String>
    {
        public Somename()
        {           

        }
        @Override
        protected String doInBackground(String... arg0) {

                    // here you put the pure processings that DO NOT affect user-interface
                getImages();  
                        getImage2();

            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            ImageAdapter imgAdp = ImageAdapter(); //your constructor of the class that triggers updates on the UI
            super.onPostExecute(result);
        }       
    }

Beware sending right context, where is required in your methods you call INSIDE the AsyncTask class. And create constructor for your ImageAdapter class to inherit data you've fetched from the sites.