Access web images application

Question

I am beginner in android app development; I have the following question: if I want to make an application where the images used are not within the project, but on the web, what is the best way to make this connection. It would be worth accessing the URL class or using the Webservice?

Answer 1

You can create a AsyncTask to load images asynchronously. See the codes below for how to do:

private class FetchImageTask extends AsyncTask<String, Integer, Bitmap> {
    @Override
    protected Bitmap doInBackground(String... arg0) {
        Bitmap b = null;
        try {
            b = BitmapFactory.decodeStream((InputStream) new URL(arg0[0]).getContent());
        }
        catch (MalformedURLException e) {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        return b;
    }
}

And to implement use this code:

new FetchImageTask() {
        @Override
        protected void onPostExecute(Bitmap result) {
            if (result != null) {
                image.setImageBitmap(result);
            }
        }
    }.execute("IMAGE_URL");

EDIT

Example on Github

Answer 2

You can solve this only in one line using the image lib, it can be both the Picasso, Glide, Universal Image Loader.Example with Picasso:

Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);

Explaining. first you pass the context of your Class, according to the Image Url and last your Imageview. It is very simple.
Link from the lib: http://square.github.io/picasso/

Answer 3

When I need to access some web content with android I use the Volley library, it is very simple to use. Here is a link to an example that requests an image:

https://developer.android.com/training/volley/request.html#request-image

Edit- Example of use:

First you add the . library jar to your project. Then you can make the request very simple: just create an instance of Stringrequest (for text), in the constructor you can explain the method you need (POST or GET), then the URL (in my example the url is in Requestcontract.XMLQuestionarioContract.XML_QUESITIONARIO_URL) and last only need to implement the system, in onResponse the return will be in the method parameter. Last only need to add the request in a queue.

 private void requestQuestionario(){
    String tag_string_req = "req_questionario"; //tag para cancelar o request

    pDialog.setMessage("Carregando Questionário...");
    showDialog();

    StringRequest stringRequest = new StringRequest(Request.Method.GET,
            RequestContract.XMLQuestionarioContract.XML_QUESITIONARIO_URL, new Response.Listener<String>() {

        @Override
        public void onResponse(String s) {
            Log.d(TAG, "Response = " + s);

            //TODO -- Tratar Response
            InputStream xml = new ByteArrayInputStream(s.getBytes());
            try {
                HashMap questionario = XmlParser.parse(xml);
                List<Questao> questoes = (List) questionario.get("questoes");
                List<Alternativa> alternativas = (List) questionario.get("alternativas");
                List<Codigo> codigos = (List) questionario.get("codigos");

                DataBaseHelper db = new DataBaseHelper(getApplicationContext());

                db.insertQuestoes(questoes);
                db.insertAlternativas(alternativas);
                db.insertCodigos(codigos);

            } catch (XmlPullParserException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (SQLException e){
                e.printStackTrace();
            }

            hideDialog();
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError volleyError) {
            //TODO -- Tratar erro
            Log.e(TAG, "Erro no request");
            hideDialog();
        }
    });

    requestQueue = RequestManager.getInstance(this).getRequestQueue();

    stringRequest.setTag(tag_string_req);
    requestQueue.add(stringRequest);
}

In this example I use the contents of onResponse’s String(String s) to make the Parsing of an XML, but it could be any String or even a Json.

For Requestqueue the Google Documentation recommends using a Singleton, but can be instantiated as follows:

RequestQueue queue = Volley.newRequestQueue(this);

To request an image in the google documentation use this example:

ImageView mImageView;
String url = "http://i.imgur.com/7spzG.png";
mImageView = (ImageView) findViewById(R.id.myImage);
...

// Retrieves an image specified by the URL, displays it in the UI.
ImageRequest request = new ImageRequest(url,
   new Response.Listener<Bitmap>() {
       @Override
       public void onResponse(Bitmap bitmap) {
           mImageView.setImageBitmap(bitmap);
       }
   }, 0, 0, null,
   new Response.ErrorListener() {
       public void onErrorResponse(VolleyError error) {
           mImageView.setImageResource(R.drawable.image_load_error);
       }
   });
  // Access the RequestQueue through your singleton class.
  MySingleton.getInstance(this).addToRequestQueue(request);

Stringrequest was replaced by an Imagerequest and onResponse parameter with a Bitmap