private class DownloadTask extends AsyncTask<URL,Void,Bitmap>{
        // Before the tasks execution
        protected void onPreExecute(){
            // Display the progress dialog on async task start
            mProgressDialog.show();
        }

        // Do the task in background/non UI thread
        protected Bitmap doInBackground(URL...urls){
            URL url = urls[0];
            HttpURLConnection connection = null;

            try{
                // Initialize a new http url connection
                connection = (HttpURLConnection) url.openConnection();

                // Connect the http url connection
                connection.connect();

                // Get the input stream from http url connection
                InputStream inputStream = connection.getInputStream();

                /*
                    BufferedInputStream
                        A BufferedInputStream adds functionality to another input stream-namely,
                        the ability to buffer the input and to support the mark and reset methods.
                */
                /*
                    BufferedInputStream(InputStream in)
                        Creates a BufferedInputStream and saves its argument,
                        the input stream in, for later use.
                */
                // Initialize a new BufferedInputStream from InputStream
                BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);

                /*
                    decodeStream
                        Bitmap decodeStream (InputStream is)
                            Decode an input stream into a bitmap. If the input stream is null, or
                            cannot be used to decode a bitmap, the function returns null. The stream's
                            position will be where ever it was after the encoded data was read.

                        Parameters
                            is InputStream : The input stream that holds the raw data
                                              to be decoded into a bitmap.
                        Returns
                            Bitmap : The decoded bitmap, or null if the image data could not be decoded.
                */
                // Convert BufferedInputStream to Bitmap object
                Bitmap bmp = BitmapFactory.decodeStream(bufferedInputStream);

                // Return the downloaded bitmap
                return bmp;

            }catch(IOException e){
                e.printStackTrace();
            }finally{
                // Disconnect the http url connection
                connection.disconnect();
            }
            return null;
        }

        // When all async task done
        protected void onPostExecute(Bitmap result){
            // Hide the progress dialog
            mProgressDialog.dismiss();

            if(result!=null){
                // Display the downloaded image into ImageView
                mImageView.setImageBitmap(result);

                // Save bitmap to internal storage
                Uri imageInternalUri = saveImageToInternalStorage(result);
                // Set the ImageView image from internal storage
                mImageViewInternal.setImageURI(imageInternalUri);
            }else {
                // Notify user that an error occurred while downloading image
                Snackbar.make(mCLayout,"Error",Snackbar.LENGTH_LONG).show();
            }
        }
    }

    // Custom method to convert string to url
    protected URL stringToURL(String urlString){
        try{
            URL url = new URL(urlString);
            return url;
        }catch(MalformedURLException e){
            e.printStackTrace();
        }
        return null;
    }

    // Custom method to save a bitmap into internal storage
    protected Uri saveImageToInternalStorage(Bitmap bitmap){
        // Initialize ContextWrapper
        ContextWrapper wrapper = new ContextWrapper(getApplicationContext());

        // Initializing a new file
        // The bellow line return a directory in internal storage
        File file = wrapper.getDir("Images",MODE_PRIVATE);

        // Create a file to save the image
        file = new File(file, "UniqueFileName"+".jpg");

        try{
            // Initialize a new OutputStream
            OutputStream stream = null;

            // If the output file exists, it can be replaced or appended to it
            stream = new FileOutputStream(file);

            // Compress the bitmap
            bitmap.compress(Bitmap.CompressFormat.JPEG,100,stream);

            // Flushes the stream
            stream.flush();

            // Closes the stream
            stream.close();

        }catch (IOException e) // Catch the exception
        {
            e.printStackTrace();
        }

        // Parse the gallery image url to uri
        Uri savedImageURI = Uri.parse(file.getAbsolutePath());

        // Return the saved image Uri
        return savedImageURI;
    }