Show image in listview from url with Android Studio

Instead of putting together a church arch to download the image asynchronously, you could use an external library that already does everything for you, reducing the work to literally a single line. I recommend Picasso .

You must import the library in your gradle:

compile 'com.squareup.picasso:picasso:(insert latest version)'

Applying it to your code, the getview of the adapter should look something like this:

@Override 
public View getView(int i, View view, ViewGroup viewGroup) {
  ViewGroup viewGroup1 (ViewGroup)layoutInflater.inflate(R.layout.lista,null);
  img=(ImageView)viewGroup1.findViewById(R.id.img);
  tposicion=(TextView)viewGroup1.findViewById(R.id.txt1);
  thora=(TextView)viewGroup1.findViewById(R.id.txt2);

  String urlfinal="http://192.168.2.19/android/control/img/" + imagen.get(i).toString();
  Rect rect = new Rect(img.getLeft(),img.getTop(),img.getRight(),img.getBottom());

  Picasso.with(ctx).load(urlfinal).into(img); //con una línea te descarga asíncronamente la imagen y te la inserta en tu imageview. Awesome =)

  tposicion.setText(posicion.get(i).toString());
  thora.setText(hora.get(i).toString());
  return viewGroup1;
}

Regarding the loading of the images from a url you can use several options, I add 3:

• GLIDE

is usually done is to load the images from resources or from a url, the dependency is added within the file build.gradle :

repositories {
  mavenCentral()
  google()
}

dependencies {
  implementation 'com.github.bumptech.glide:glide:4.6.1'
  annotationProcessor 'com.github.bumptech.glide:compiler:4.6.1'
}

this is an example:

//Obtienes la referencia del ImageView en donde se cagaría la imagen.
ImageView imageView = (ImageView) findViewById(R.id.imageView);

//Indicas a Glide que imagen cargar y en que vista.
Glide.with(context)
    .load("http://www.midominio.com/myimagen.jpg")
    .into(imageView);

The interesting thing about Glide is that it manages the cache and memory required to process the image in an optimal way, in addition to that it is much easier to implement with respect to Universal Image Loader .

• PICASSO

very similar to Glide, it also includes cache management. Add the dependency within the build.gradle file

compile 'com.squareup.picasso:picasso:2.71828'

and this is an example:

Picasso.
  with(context).
  load("http://www.midominio.com/myimagen.jpg").
  into(imageView);

• AsynctTask

How to download image in an ImageView using AsynctTask.

You create an Asynctask where the download process is done within the doInBackground() method:

class LoadImage extends AsyncTask<String, Void, Bitmap> {

    private final WeakReference<ImageView> imageViewReference;

    public LoadImage(ImageView imageView) {
        imageViewReference = new WeakReference<ImageView>(imageView);
    }

    @Override
    protected Bitmap doInBackground(String... params) {
        try {
            return downloadBitmap(params[0]);
        } catch (Exception e) {
            Log.e("LoadImage class", "doInBackground() " + e.getMessage());
        }
        return null;
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        if (isCancelled()) {
            bitmap = null;
        }

        if (imageViewReference != null) {
            ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                if (bitmap != null) {
                    imageView.setImageBitmap(bitmap);
                }
            }
        }
    }

    private Bitmap downloadBitmap(String url) {
        HttpURLConnection urlConnection = null;
        try {
            URL uri = new URL(url);
            urlConnection = (HttpURLConnection) uri.openConnection();
            int statusCode = urlConnection.getResponseCode();
            if (statusCode != HttpURLConnection.HTTP_OK) {
                return null;
            }

            InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                return bitmap;
            }
        } catch (Exception e) {
            urlConnection.disconnect();
            Log.e("LoadImage class", "Descargando imagen desde url: " + url);
        } finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
        }
        return null;
    }
}

and you would call in this way the AsyncTask to load the downloaded image, defining the container ImageView and the url of the image to download:

   private ImageView imageView;
   private String imageHttpAddress = "http://jonsegador.com/wp-content/apezz.png";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = (ImageView) findViewById(R.id.image_view);
        //downloadFile(imageHttpAddress);
        //AsyncTask recibe la referencia del ImageView y la url a descargar.
        new LoadImage(imageView).execute(imageHttpAddress);
    }

to get: