Question

I’ve implemented a ListView for reading an rss feed and I would like to implement an autoscroll for this list view.

I’ve probably to use something like:

listView.post(new Runnable() {
            @Override
            public void run() {
                listView.smoothScrollToPosition(???);
            }
        });

but how to read smoothly all the position and then start from the top again?

Answer 1

Well, you could simply iterate through the elements in the list view by using some sort of counter:

int count = listView.getCount();
for (int i = 0; i < count; i++) {
    listView.post(new Runnable() {
        @Override
        public void run() {
            listView.smoothScrollToPosition(i);
        }
    }); 
}
// Once the method gets to here, i == count and we're at the last position
// So you can use some logic to scroll back to the top e.g. 
// listView.smoothScrollToPosition(0)

Instead of using post(), you may want to think about using a Timer object instead, as I believe there isn’t much control about when runnable’s on the post queue are executed.

EDIT

So I managed to get a rudimentary, but working, example by using a Timer with a fixed-rate scheduled ScrollTimerTask

//This is an inner class, with i an int in the Activity, starting at 0;
public class ScrollTimerTask extends TimerTask {

    @Override
    public void run() {
        if (i < getListView().getCount()) {
            getListView().smoothScrollToPosition(i);
            i++;
        }
        else {
            getListView().smoothScrollToPosition(0);
            i == 0;
        }
}

Then, where you want to start moving down the list call new Timer().scheduleAtFixedRate(new ScrollTimerTask(), 0, 1000);. This will start scrolling after no delay, and will schedule the scrolling task every 1000ms.

Note this is rudimentary and will crash the Activity when you close it, and runs continuously. To prevent the crash, I’d recommend keeping a reference to the Timer object and calling Timer.cancel() in the Activity’s onPause() method. But it is a starting block!