una - thread android studio ejemplo

Diálogo de progreso de Android no se muestra en AsyncTask

Question

Alguien por favor revisa mis códigos. Mi diálogo de progreso simplemente aparece y descarta tan rápido antes de que pudiera verlo. Se supone que debe mostrar un diálogo de progreso durante el proceso de descarga. Pero mi diálogo de progreso se cierra antes de que se cargue la imagen.

public class SingleImageViewActivity  extends SherlockActivity {

        // XML node keys
    static final String KEY_TITLE = "title";
    static final String KEY_ARTIST = "artist";  
    static final String KEY_THUMB_URL = "thumb_url";
    static final String KEY_BIG_URL = "big_url";
    private ProgressDialog pDialog;
    String title;
    String artist;
    //String image_url;
    String big_image_url;
    ImageView view;
    Intent intent;
    Context context;
    ShareActionProvider mShareActionProvider;
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.single_view_item);
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            //checkInternetConnection();

            new loadSingleView().execute();
            view = (ImageView) findViewById(R.id.single_image);    

        }

    public class loadSingleView extends AsyncTask<String, String, String> {

            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                pDialog = new ProgressDialog(SingleImageViewActivity.this);
                pDialog.setTitle("Connect to Server");
                pDialog.setMessage("This process can take a few seconds to a few minutes, depending on your Internet Connection Speed.");
                pDialog.setIndeterminate(false);
                pDialog.setCancelable(false);
                pDialog.show();
            }
            @Override
            protected String doInBackground(String... args) {
                // updating UI from Background Thread


                Intent in = getIntent();

                //image_url = in.getStringExtra(KEY_THUMB_URL);
                big_image_url = in.getStringExtra(KEY_BIG_URL);
                title = in.getStringExtra(KEY_TITLE);
                artist = in.getStringExtra(KEY_ARTIST);

                SingleViewImageLoader imgLoader = new SingleViewImageLoader(getApplicationContext());

                imgLoader.DisplayImage(big_image_url, view);
                return null;

                        }
            @Override       
            protected void onPostExecute(String args) {
                // dismiss the dialog after getting all products
                 TextView lblName = (TextView) findViewById(R.id.name_title);
                    TextView lblCost = (TextView) findViewById(R.id.name_artist);



                    lblName.setText(title);
                    lblCost.setText(artist);

                    ActionBar ab = getSupportActionBar();
                    ab.setTitle(title);
                    ab.setSubtitle(artist);




                pDialog.dismiss();


            }


    }

SingleViewImageLoader.class

public class SingleViewImageLoader {

    MemoryCache memoryCache=new MemoryCache();
    FileCache fileCache;
    private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
    ExecutorService executorService; 

    public SingleViewImageLoader(Context context){
        fileCache=new FileCache(context);
        executorService=Executors.newFixedThreadPool(5);
    }

   final int stub_id = R.drawable.no_image;
    public void DisplayImage(String url, ImageView imageView)
    {
        imageViews.put(imageView, url);
        Bitmap bitmap=memoryCache.get(url);
        if(bitmap!=null)
            imageView.setImageBitmap(bitmap);
        else
        {
            queuePhoto(url, imageView);
            imageView.setImageResource(stub_id);

        }
    }

    private void queuePhoto(String url, ImageView imageView)
    {
        PhotoToLoad p=new PhotoToLoad(url, imageView);
        executorService.submit(new PhotosLoader(p));
    }

    private Bitmap getBitmap(String url) 
    {
        File f=fileCache.getFile(url);

        //from SD cache
        Bitmap b = decodeFile(f);
        if(b!=null)
            return b;

        //from web
        try {
            Bitmap bitmap=null;
            URL imageUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setInstanceFollowRedirects(true);
            InputStream is=conn.getInputStream();
            OutputStream os = new FileOutputStream(f);
            Utils.CopyStream(is, os);
            os.close();
            bitmap = decodeFile(f);
            return bitmap;
        } catch (Exception ex){
           ex.printStackTrace();
           return null;
        }
    }

    //decodes image and scales it to reduce memory consumption
    private Bitmap decodeFile(File f){
        try {
            //decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f),null,o);

            //Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE=500;
            int width_tmp=o.outWidth, height_tmp=o.outHeight;
            int scale=1;
            while(true){
                if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                    break;
                width_tmp/=2;
                height_tmp/=2;
                scale*=2;
            }

            //decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize=scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {}
        return null;
    }

    //Task for the queue
    private class PhotoToLoad
    {
        public String url;
        public ImageView imageView;
        public PhotoToLoad(String u, ImageView i){
            url=u; 
            imageView=i;
        }
    }

    class PhotosLoader implements Runnable {
        PhotoToLoad photoToLoad;
        PhotosLoader(PhotoToLoad photoToLoad){
            this.photoToLoad=photoToLoad;
        }

        @Override
        public void run() {
            if(imageViewReused(photoToLoad))
                return;
            Bitmap bmp=getBitmap(photoToLoad.url);
            memoryCache.put(photoToLoad.url, bmp);
            if(imageViewReused(photoToLoad))
                return;
            BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
            Activity a=(Activity)photoToLoad.imageView.getContext();
            a.runOnUiThread(bd);
        }
    }

    boolean imageViewReused(PhotoToLoad photoToLoad){
        String tag=imageViews.get(photoToLoad.imageView);
        if(tag==null || !tag.equals(photoToLoad.url))
            return true;
        return false;
    }

    //Used to display bitmap in the UI thread
    class BitmapDisplayer implements Runnable
    {
        Bitmap bitmap;
        PhotoToLoad photoToLoad;
        public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
        public void run()
        {
            if(imageViewReused(photoToLoad))
                return;

            if(bitmap!=null)
                photoToLoad.imageView.setImageBitmap(bitmap);
          else
              photoToLoad.imageView.setImageResource(stub_id);

        }
    }

    public void clearCache() {
        memoryCache.clear();
        fileCache.clear();
    }



}

Answer 1

Su clase de Load Loader también usa thread para mostrar la imagen, por lo que se ejecuta en segundo plano y se invoca su método onPostExecute () y descarta el diálogo de progreso.