Question

i’ve searched and didn’t come across anything usefull on problem i’m facing.

I fetch images from remote location and store them in local cache as they are needed, when image has been downloaded i use lazy loading to update the ImageView that requested it. It all works fine, but when request comes from Gallery adapter and once the download is complete it does not seem to update only the imageView that requested it, but rather the whole GalleryView. It’s really annoying as if the user scrolls through the gallery it will jump back to last known position when one of the reqeusted images is ready to be shown.

Same happens if i’m just dragging the gallery to one side and as the new image that has just came into view is ready it jumps back to last known position and i have to dragg all over again and so on and on…

So does anybody know any workaround to update just single imageView in the gallery without affecting user scrolling?

Answer 1

I have an example for you (which I wrote myself some time ago and abstracted here):

public class MyAdapter ... {

    // you don't need a weak reference necessarily, in my case it was a more
    // common solution so I had to do that
    private List<WeakReference<ImageView>> mShownImageViews =
        new LinkedList<WeakReference<ImageView>>();

    public View getView(...) {
        if (view == null) {
            // create your view
            mShownImageViews.add(new WeakReference(theImageViewToUpdate));
        }

        // set your data

        // If you set null the image view will never be updated
        // you have to set the image here then
        imageView.setTag(imageAvailable ? null : "someUniqueIdForYourImage");
    }

    public void imageLoaded(String someUniqueIdForYourImage, Bitmap theImage) {
        for (WeakReference<ImageView> r : mShownImageViews) {
            ImageView iv = r.get();

            if (iv != null && iv.getTag() != null
                    && iv.getTag().equals(someUniqueIdForYourImage)) {
                iv.setImageBitmap(theImage);
                iv.setTag(null);
        }
    }
}