public void prioritizeViewRange(int firstVisibleItem, int lastVisibleItem, int prefetchBuffer) {
if ((lastVisibleItem < firstVisibleItem) || (sectionKeys.size() == 0)) {
return;
}
// We want to prioritize requests for items which are visible but do not have pictures
// loaded yet. We also want to pre-fetch pictures for items which are not yet visible
// but are within a buffer on either side of the visible items, on the assumption that
// they will be visible soon. For these latter items, we'll store the images in memory
// in the hopes we can immediately populate their image view when needed.
// Prioritize the requests in reverse order since each call to prioritizeRequest will just
// move it to the front of the queue. And we want the earliest ones in the range to be at
// the front of the queue, so all else being equal, the list will appear to populate from
// the top down.
for (int i = lastVisibleItem; i >= 0; i--) {
SectionAndItem<T> sectionAndItem = getSectionAndItem(i);
if (sectionAndItem.graphObject != null) {
String id = getIdOfGraphObject(sectionAndItem.graphObject);
ImageRequest request = pendingRequests.get(id);
if (request != null) {
ImageDownloader.prioritizeRequest(request);
}
}
}
// For items which are not visible, but within the buffer on either side, we want to
// fetch those items and store them in a small in-memory cache of bitmaps.
int start = Math.max(0, firstVisibleItem - prefetchBuffer);
int end = Math.min(lastVisibleItem + prefetchBuffer, getCount() - 1);
ArrayList<T> graphObjectsToPrefetchPicturesFor = new ArrayList<T>();
// Add the IDs before and after the visible range.
for (int i = start; i < firstVisibleItem; ++i) {
SectionAndItem<T> sectionAndItem = getSectionAndItem(i);
if (sectionAndItem.graphObject != null) {
graphObjectsToPrefetchPicturesFor.add(sectionAndItem.graphObject);
}
}
for (int i = lastVisibleItem + 1; i <= end; ++i) {
SectionAndItem<T> sectionAndItem = getSectionAndItem(i);
if (sectionAndItem.graphObject != null) {
graphObjectsToPrefetchPicturesFor.add(sectionAndItem.graphObject);
}
}
for (T graphObject : graphObjectsToPrefetchPicturesFor) {
URI uri = getPictureUriOfGraphObject(graphObject);
final String id = getIdOfGraphObject(graphObject);
// This URL already have been requested for pre-fetching, but we want to act in an LRU manner,
// so move
// it to the end of the list regardless.
boolean alreadyPrefetching = prefetchedProfilePictureIds.remove(id);
prefetchedProfilePictureIds.add(id);
// If we've already requested it for pre-fetching, no need to do so again.
if (!alreadyPrefetching) {
downloadProfilePicture(id, uri, null);
}
}
}
protected void populateGraphObjectView(View view, T graphObject) {
String id = getIdOfGraphObject(graphObject);
view.setTag(id);
CharSequence title = getTitleOfGraphObject(graphObject);
TextView titleView = (TextView) view.findViewById(R.id.com_facebook_picker_title);
if (titleView != null) {
titleView.setText(title, TextView.BufferType.SPANNABLE);
}
CharSequence subtitle = getSubTitleOfGraphObject(graphObject);
TextView subtitleView = (TextView) view.findViewById(R.id.picker_subtitle);
if (subtitleView != null) {
if (subtitle != null) {
subtitleView.setText(subtitle, TextView.BufferType.SPANNABLE);
subtitleView.setVisibility(View.VISIBLE);
} else {
subtitleView.setVisibility(View.GONE);
}
}
if (getShowCheckbox()) {
CheckBox checkBox = (CheckBox) view.findViewById(R.id.com_facebook_picker_checkbox);
updateCheckboxState(checkBox, isGraphObjectSelected(id));
}
if (getShowPicture()) {
URI pictureURI = getPictureUriOfGraphObject(graphObject);
if (pictureURI != null) {
ImageView profilePic = (ImageView) view.findViewById(R.id.com_facebook_picker_image);
// See if we have already pre-fetched this; if not, download it.
if (prefetchedPictureCache.containsKey(id)) {
ImageResponse response = prefetchedPictureCache.get(id);
profilePic.setImageBitmap(response.getBitmap());
profilePic.setTag(response.getRequest().getImageUri());
} else {
downloadProfilePicture(id, pictureURI, profilePic);
}
}
}
}