Android ListView task: apparently 3 items, scrolled the rest?

Question

Android

Kind time of day to you people...
Actually the task is described in a question. I understand the essence of the solution - I need a custom adapter in which this is implemented. It is possible to get visible elements (first, last, total number of elements, etc. in onScroll), like a simple check (>/= 3) and do setVisibility(View.HIDE/VISIBLE), but for the life of me I can’t to do this, not to find an example in google ...
I've only spent the second month with Android / Java and maybe my problem and not a problem at all. But maybe someone knows how to show an example of how to do this.

Answer 1

You just need a scroll listener.
1. Make a thread method that will load\take from the database with the pagination parameter.
2. By default, it loads the first page, let's say 3 elements, parses what is needed there, feeds it to a regular adapter, etc.
3. Attach a listener to it

public class EndlessScrollListener implements OnScrollListener {

        private int visibleThreshold = 5;
        private int currentPage = 0;
        private int previousTotal = 0;
        private boolean loading = true;

        public EndlessScrollListener() {
        }
        public EndlessScrollListener(int visibleThreshold) {
            this.visibleThreshold = visibleThreshold;
        }

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem,
                int visibleItemCount, int totalItemCount) {
            if (loading) {
                if (totalItemCount > previousTotal) {
                    loading = false;
                    previousTotal = totalItemCount;
                    currentPage++;
                }
            }
            if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
                // I load the next page of gigs using a background task,
                // but you can call any function here.
                new LoadGigsTask().execute(currentPage + 1);
                loading = true;
            }
        }

        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
        }
    }

benjii.me/2010/08/endless-scrolling-listview-in-android
4. When scrolling, it will increment currentPage, and, where in the example new LoadGigsTask().execute(currentPage + 1), call your method, which will load not 3, but 6, 9, 12 and load this case into the adapter.
There, depending on whether this data is from the database, from the provider or from the Internet - the logic may change slightly, but the essence is always the same - a scroll listener that remembers the current page.
UPD: you don’t need to load 100, show 3, and hide 97 - if the user needs 3 to start, then exactly 3 should be loaded.

Answer 2

And why not measure the size of one field (list item) and set the size in the ListView to be field_size*3. Then only three will be visible, the rest will scroll. Or is this not suitable?