I spent several hours tweaking my own loading of images into an Android ListView. The problem was that the images would not load until I scrolled the screen and even then the lag was unacceptable.
My program performed the following:
Download a non indexed list of geotag data that includes the image URL into ArrayList rowdatalist
Loop through the rows in rowdatalist and Async create the bitmap from the image URL in each row
The customRowAdapter for the ListView will have a ViewHolder that sets the holder.imageView from the bitmap decoded from the URL.
Essentially, this produces statements like the following:
holder.imageView = (ImageView) convertView.findViewById(R.id.row_image);
holder.imageView.setImageBitmap(rowdata.getBitmap());
This is from inside the object rowdata
public Bitmap getBitmap() {
if (bitmapurl != null && !bitmapurl.equals("")) {
new ImageLoadAsync(context).execute(bitmapurl);
} else {
// default image if nothing from url
bitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.war4a);
}
return bitmap;
}
This is the background thread portion of the
Async call:
@Override
protected Bitmap doInBackground(String... urls) {
String surl = urls[0];
Bitmap bm = null;
try {
URL imageUrl = new URL(surl);
bm = BitmapFactory.decodeStream(imageUrl.openStream());
} catch (IOException e) {
e.printStackTrace();
bm = BitmapFactory.decodeResource(context.getResources(), R.drawable.war4a);
}
return bm;
}
This is just a portion of the cumbersome code. As an experienced programmer, I should have known not to reinvent the wheel, but I just could not help myself
At the end of the day, this line of code replaced all that nonsense
Picasso.with(context).load(rowdata.getBitmapUrl()).into(holder.imageView);
