Pagination Of ListView On Scrolling In Xamarin.Android - xamarin.android

Question

Can Any one help Me on How to Implement on Handling Pagination on Scrolling of listview in xamarin.android .any link or any sample wil be helpful

Answer 1

Well, Android pagination is quite easy in comparison to iOS and can be done as follows:
public class EndlessScrollListener : Java.Lang.Object, Android.Widget.AbsListView.IOnScrollListener
{
private int visibleThreshold = 5;
private int currentPage = 0;
private int previousTotal = 0;
private bool loading = true;
public EndlessScrollListener()
{
}
public EndlessScrollListener(int visibleThreshold)
{
this.visibleThreshold = visibleThreshold;
}
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;
}
}
public void OnScrollStateChanged(AbsListView view, [GeneratedEnum] ScrollState scrollState)
{
// throw new NotImplementedException();
}
}
Then set it to the listview as follows:
List.SetOnScrollListener(new EndlessScrollListener());
Working of code:
visibleThreshold – The minimum amount of items to have below your current scroll position, before loading more.
currentPage – The current page of data you have loaded.
previousTotal – The total number of items in the dataset after the last load.
loading – True if we are still waiting for the last set of data to load.
Next, we have a couple of constructors that allow us to set the visibleThreshold inline if we want.
The first overridden method we have is called every time the list is scrolled. This happens many times a second during a scroll, so be wary of the code you place here. We are given a few useful parameters to help us work out if we need to load some more data, but first, we check if we are waiting for the previous load to finish.
If it’s still loading, we check to see if the dataset count has changed, if so we conclude it has finished loading and update the current page number and total item count.
If it isn’t currently loading, we check to see if we have breached the visibleThreshold and need to reload more data. If we do need to reload some more data, we execute a background task and set the loading flag to true. Thus solving the problem forever!
The last method in the class we do not need, however, if you’re interested, it is primarily used for tracking changes in the scroll action itself via the scrollState parameter.
Finally, the code to call the class creates a new instance of EndlessScrollListener and bind’s it to a ListView of mine. Of course, put your own ListView in place of List.