Appel de procédure distante sous Android

public class MyScreen extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //Mise en place des vues ici
    }

    @Override
    protected void onStart() {
        super.onStart() ;
        //Ordonne l'appel asynchrone avec des arguments de type X
        new MyRPC(this).execute(arg1, arg2, arg3, ...) ;
    }

    public void populate(Z data) {
        //Mise à jour des vues avec data de type Z
    }
        
}

public class MyRPC extends AsyncTask<X, Y, Z> {
    
    private volatile MyScreen screen;  //référence à l'écran
    private HttpClient client;         //référence au client HTTP

    public MyRPC(MyScreen s) {
        this.screen = s ;
        this.client = new DefaultHttpClient();
    }
    
    @Override
    protected void onPreExecute() {
        //prétraitement de l'appel
    }

    @Override
    protected Z doInBackground(X… params) {
        //Appel de procédure distante via HTTP (traitement long)
        Z obj = this.client.execute(url_with_params);
        return obj; //Objet de type Z automatiquement réinjecté en entrée de onPostExecute()
    }

    @Override
    protected void onPostExecute(Z result) {
        //post-traitement de l'appel
        this.screen.populate(result); //callback
    }
    
}

public class ImageScreen extends Activity {

    private ImageView viewer;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.image_activity);
        this.viewer = (ImageView) findViewById(R.id.imageView1);
    }

    @Override
    protected void onStart() {
        super.onStart();
        new DownloadImage(this).execute("qr","200x200","Coucou");
    }

    public void populate(Bitmap data) {
        this.viewer.setImageBitmap(data);
    }
    
}

public class DownloadImage extends AsyncTask<String, Void, Bitmap> {

    private static final String BASE_URL = "http://chart.apis.google.com/chart";
    
    private volatile ImageScreen screen;
    private HttpClient client;
    private ProgressDialog progress;
    
    public DownloadImage(ImageScreen s) {
        this.screen = s;    
        this.client = new DefaultHttpClient();
        this.progress = new ProgressDialog(this.screen);
    }
    
    @Override
    protected void onPreExecute() {                           
        this.progress.setTitle("Veuillez patienter");
        this.progress.setMessage("Récupération de l'image en cours...");
        this.progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);      
        this.progress.show();
    }
    
    @Override
    protected Bitmap doInBackground(String... params) {
    
        Bitmap dummyImage = null;
        
        try {
            
            String url = String.format("%s?cht=%s&chs=%s&chl=%s", BASE_URL, params[0], params[1], params[2]);        
            HttpGet request = new HttpGet(url);
            HttpResponse response = this.client.execute(request);    
            HttpEntity entity = response.getEntity();
            byte[] bytes = EntityUtils.toByteArray(entity);
            dummyImage = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                        
        } catch (Exception e) { Log.e("RPC","Exception levée", e); }
        
        return dummyImage;
    }

    @Override
    protected void onPostExecute(Bitmap result) {
                
        if(this.progress.isShowing()) this.progress.dismiss();        
        this.screen.populate(result);
    }
    
}

public class LoremScreen extends ListActivity {

    private ArrayAdapter<String> adapter;
    
    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.lorem_activity);  
        this.adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);     
        this.setListAdapter(adapter);
    }
    
    @Override
    protected void onStart() {
        super.onStart();
        new DownloadLorem(this).execute();
    }

    public void populate(ArrayList<String> data) {
        this.adapter.clear();
        this.adapter.addAll(data);
        this.adapter.notifyDataSetChanged();
    }
    
}

public class DownloadLorem extends AsyncTask<Void, Void, ArrayList<String>> {

    private static final String BASE_URL = "http://loripsum.net/api/plaintext/short/20/";
    private LoremScreen screen;
    private HttpClient client;
    private ProgressDialog progress;
    
    public DownloadLorem(LoremScreen s) {
        this.screen = s;    
        this.client = new DefaultHttpClient();
        this.progress = new ProgressDialog(this.screen);
    }
    
    @Override
    protected void onPreExecute() {                           
        progress.setTitle("Veuillez patienter");
        progress.setMessage("Récupération des données en cours...");
        progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);      
        progress.show();
    }
    
    @Override
    protected ArrayList<String> doInBackground(Void... params) {
    
        InputStream content = null;
        ArrayList<String> dummyTexts = new ArrayList<String>();
        
        try {
            HttpResponse response = this.client.execute(new HttpGet(BASE_URL));
            content = response.getEntity().getContent();            
            Scanner scanner = new Scanner(new InputStreamReader(content));
            scanner.useDelimiter("\\s*\n");
            while (scanner.hasNext()) { dummyTexts.add(scanner.next().substring(0,30).concat("...")) ; }
            
        } catch (Exception e) { Log.e("RPC","Exception levée", e); }
        
        return dummyTexts;
    }

    @Override
    protected void onPostExecute(ArrayList<String> result) {
            
        if(progress.isShowing()) progress.dismiss();    
        this.screen.populate(result);
    }
    
}

public class LogScreen extends Activity {

    private TelephonyManager tm;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.log_activity);

        tm = (TelephonyManager) this.getSystemService(Context.TELEPHONY_SERVICE);
        new NotifyLogger().execute(tm.getDeviceId(), "CONNECT");
    }
    
    @Override
    protected void onDestroy() {
        super.onDestroy();
        new NotifyLogger().execute(tm.getDeviceId(), "DISCONNECT");
    }
    
}

public class NotifyLogger extends AsyncTask<String, Void, Void> {

    private static final Object BASE_URL = "http://my.company.com/remote/logUserConnexion.php";
    
    private HttpClient client;
    
    public NotifyLogger() {
        this.client = new DefaultHttpClient();
    }
    
    @Override
    protected Void doInBackground(String... params) {

        try {
            String url = String.format("%s?id=%s&event=%s", BASE_URL, params[0], params[1]);        
            HttpGet request = new HttpGet(url);
            this.client.execute(request);
        } catch (Exception e) { Log.e("RPC","Exception levée", e); }
        
        return null;
    }

}

public class VolleyImageScreen extends Activity implements Response.Listener<Bitmap> {

    private ImageView viewer;
    private ProgressDialog progress;
    
    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.image_activity);
        this.viewer = (ImageView) findViewById(R.id.imageView1);    
    }

    @Override
    protected void onStart() {
        super.onStart();
        
        this.progress = new ProgressDialog(this);
        this.progress.setTitle("Veuillez patientez");
        this.progress.setMessage("Récupération de l'image en cours...");
        this.progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);      
        this.progress.show();
        
        // Instancie la file de message (cet objet doit être un singleton)
        RequestQueue queue = Volley.newRequestQueue(this);
        String url ="http://chart.apis.google.com/chart?cht=qr&chs=200x200&chl=Coucou";

        // Requête d'une image à l'URL demandée
        ImageRequest picRequest = new ImageRequest(url, this, 0, 0, null, null);
        // Insère la requête dans la file
        queue.add(picRequest);
    }


    @Override
    public void onResponse(Bitmap response) { //callback en cas de succès
        
        if(this.progress.isShowing()) this.progress.dismiss();        
        this.viewer.setImageBitmap(response);        
    }
    
}