/// <summary>
/// Launch the loading of a data page.
/// If a task is currently running, it gets discarded (callbacks won't be called).
/// If the first page loading is asked whereas one or several pages have already been loaded, a "refresh" is detected.
/// </summary>
/// <param name="pageNumber">The page number to load (pageNumber = 1 for the first page).</param>
/// <param name="calledFromScroll">True if LoadPage has been called from OnScroll method of the IInfiniteListLoader.</param>
public Task <PageResult <TResult> > LoadPage(int pageNumber, bool calledFromScroll = false)
{
Contract.Requires(() => pageNumber > 0);
Contract.Requires(
() => calledFromScroll || (pageNumber == 1 || pageNumber == (PageLoadedCount + 1)),
"The paginator can only load sequential pages");
InternalLogger.Info($"Requesting page n°{pageNumber} load, {PageLoadedCount} pages loaded so far");
lock (_syncRoot)
{
if (calledFromScroll)
{
if (pageNumber <= PageLoadedCount)
{
InternalLogger.Info($"Aborting IInfiniteListLoader call: only a direct call to LoadPage can lead to a refresh");
return(Task.FromResult(PageResult <TResult> .Empty));
}
}
if (pageNumber > PageLoadedCount && IsFull)
{
InternalLogger.Info($"Cannot load page {pageNumber} total item count has already been reached ({TotalCount})");
return(Task.FromResult(PageResult <TResult> .Empty));
}
if (pageNumber == 1 && PageLoadedCount > 0)
{
InternalLogger.Info("Refresh detected");
_refreshRequested = true;
}
else
{
_refreshRequested = false;
}
if (LoadingTask != null && LoadingTask.IsNotCompleted)
{
// Cancels callbacks of previous task if not completed
LoadingTask.CancelCallbacks();
}
LoadingTask = new TaskMonitor <PageResult <TResult> > .Builder(
() => _pageSourceLoader(pageNumber, PageSize, _refreshRequested))
.WithWhenSuccessfullyCompleted(OnPageRetrieved)
.WithWhenCompleted(OnTaskCompleted)
.Build();
InternalLogger.Info($"Page n°{pageNumber} loading started");
LoadingTask.Start();
return(LoadingTask.Task);
}
}
