I have recently found a thread here, as I have to do a similar thing for a listview with images, but the principle is simple, as you can read in the first sample class shown there (by jleedev).
You get the Input stream of the image (from web)
private InputStream fetch(String urlString) throws MalformedURLException, IOException {
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpGet request = new HttpGet(urlString);
HttpResponse response = httpClient.execute(request);
return response.getEntity().getContent();
}
Then you store the image as Drawable and you can pass it to the ImageView (via setImageDrawable). Again from the upper code snippet take a look at the entire thread.
InputStream is = fetch(urlString);
Drawable drawable = Drawable.createFromStream(is, "src");