Question

Here is the paint method of my custom field:

   protected void paint(Graphics graphics) {

            new downloadImage();
            Bitmap img =  downloadImage.connectServerForImage(this.poster);


            graphics.drawBitmap(0, 0, 100, 150, img, LEFT, TOP);
     }

Here is the connectServerForImage method:

public static Bitmap connectServerForImage(String url) {

          HttpConnection httpConnection = null;
          DataOutputStream httpDataOutput = null;
          InputStream httpInput = null;
          int rc;

          Bitmap bitmp = null;
          try {
           httpConnection = (HttpConnection) Connector.open(url);
           rc = httpConnection.getResponseCode();
           if (rc != HttpConnection.HTTP_OK) {
            throw new IOException("HTTP response code: " + rc);
           }
           httpInput = httpConnection.openInputStream();
           InputStream inp = httpInput;
           byte[] b = IOUtilities.streamToBytes(inp);
           EncodedImage hai = EncodedImage.createEncodedImage(b, 0, b.length);
           return hai.getBitmap();

          } catch (Exception ex) {
           System.out.println("URL Bitmap Error........" + ex.getMessage());
          } finally {
           try {
            if (httpInput != null)
             httpInput.close();
            if (httpDataOutput != null)
             httpDataOutput.close();
            if (httpConnection != null)
             httpConnection.close();
           } catch (Exception e) {
            e.printStackTrace();

           }
          }
          return bitmp;
         }

I’m putting multiple instances of my custom field into a verticalfieldmanager, but the images slows the scrolling down. It seems as if every time I scroll it runs the paint method again even though the image has already been downloaded.

I’m thinking I will need to download the images in another thread? Someone lead me in the right direction.

Answer 1

1. You must start any HTTP interaction in a separate thread (no blocking call).
2. To avoid downloading same image multiple times cache already downloaded image. You can use image download URL as image tag to store
   them.
3. Every time there is a event on screen, paint method will be called. So don’t start download an image if it is already downloaded.