public override View GetView(int position, View convertView, ViewGroup parent)
{
if (convertView == null)
{
convertView = new ImageView(ContextProp);
convertView.LayoutParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MatchParent, ViewGroup.LayoutParams.MatchParent);
// set size initially to fill whole screen. otherwise because of no height PdfPageGenerationTask will attempt to load all pages
IWindowManager windowManager = Context.GetSystemService(Context.WindowService).JavaCast <IWindowManager>();
Display disp = windowManager?.DefaultDisplay;
if (disp != null)
{
Android.Graphics.Point screenSize = new Android.Graphics.Point();
disp.GetSize(screenSize);
Android.Graphics.Bitmap pdfPageStartBitmap = Android.Graphics.Bitmap.CreateBitmap((int)(screenSize.X - HorizontalMarginsForView), (int)(screenSize.Y - VerticalMarginsForView), Android.Graphics.Bitmap.Config.Argb4444);
((ImageView)convertView).SetImageDrawable(new BitmapDrawable(ContextProp.Resources, pdfPageStartBitmap));
}
}
// on zoom do not cancel previous tasks so zooming is visible and performed on all visible views
// on scrolling lets just focus on newest task
bool isZooming = false;
int tasksHistoryRelevant = 1;
if (parent is PdfListView)
{
isZooming = ((PdfListView)parent).ScalingStatus != PdfListView.ScalingStatusValues.Idle;
tasksHistoryRelevant = ((PdfListView)parent).VisibleItemCount;
}
// on scrolling hide reused views untill shown again so they do not show old content
if (!isZooming)
{
((ImageView)convertView).Visibility = ViewStates.Invisible;
}
PdfPageGenerationTask newPdfViewTask = new PdfPageGenerationTask((ImageView)convertView, this);
newPdfViewTask.TaskIndex = position;
SetPageGenerationTaskMngr(newPdfViewTask, tasksHistoryRelevant);
newPdfViewTask.Execute(_url, position.ToString(), _zoom.ToString());
return(convertView);
}
void SetPageGenerationTaskMngr(PdfPageGenerationTask pdfGenerationTask, int tasksHistoryRelevant)
{
if (_pdfPageGenerationTasks.Count > 1)
{
int historyRelevantCounter = 0;
for (int i = _pdfPageGenerationTasks.Count - 1; i >= 0; i--)
{
historyRelevantCounter++;
if (historyRelevantCounter > tasksHistoryRelevant)
{
_pdfPageGenerationTasks[i].Value.Cancel(false);
_pdfPageGenerationTasks.RemoveAt(i);
}
}
}
_pdfPageGenerationTasks.Add(new KeyValuePair <int, PdfPageGenerationTask>(pdfGenerationTask.TaskIndex, pdfGenerationTask));
}
