private async void RequestImageForCell(UIEntityTableViewCell <TEntity> cell, NSIndexPath indexPath)
{
UIImage image = this.TryGetImageForCell(cell);
if (image != null)
{
cell.SetImage(image);
}
else
{
string imageUrl = cell.ImageUrl;
RemoteImageRequest imageRequest = this.imageCatalog.StartImageRequest(imageUrl, cell.ImageOptions);
if (!imageRequest.IsRequestCompleted)
{
cell.SetImageDownloadInProgress();
}
ServiceResult result = await imageRequest.Task;
// Check if the requesting cell was new and ensure that it hasn't already been reused.
if (indexPath.Length == 0 && imageUrl == cell.ImageUrl)
{
this.SetImageFromResult(result, cell);
}
else
{
this.SetImageFromResult(result, indexPath);
}
}
}
private void SetImageFromResult(ServiceResult result, NSIndexPath indexPath)
{
if (!this.isDisposed)
{
UIEntityTableViewCell <TEntity> cell = this.TableView.CellAt(indexPath) as UIEntityTableViewCell <TEntity>;
this.SetImageFromResult(result, cell);
}
}
/// <summary>
/// Attempts to get the image that should be displayed with the specified cell if it is available locally.
/// </summary>
/// <param name="cell">The cell to get the image for.</param>
/// <returns>The image for the cell or null if an image is not currently available.</returns>
protected virtual UIImage TryGetImageForCell(UIEntityTableViewCell <TEntity> cell)
{
if (this.imageCatalog == null)
{
throw new InvalidOperationException("A remote image catalog has not been set so remote image downloading is not available.");
}
return
(this.imageCatalog.TryGetImage(
cell.ImageUrl,
cell.ImageOptions,
bytes => UIImageByteConverter.FromBytes(bytes, decompress: true)));
}
/// <summary>
/// Gets the cell for the specified table at the given index.
/// </summary>
/// <param name="tableView">The table view.</param>
/// <param name="indexPath">The index path.</param>
/// <returns>A table view cell.</returns>
public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
{
if (this.IsLoadingIndicator(indexPath))
{
return(this.createLoadingMorePagesCell());
}
TEntity entity = this.items.ElementAt(indexPath.Row);
UIEntityTableViewCell <TEntity> cell = this.createTableCell(entity);
cell.Initialize(entity);
if (cell.IsRemoteImageSupported)
{
this.requestImageForCell(cell, indexPath);
}
return(cell);
}
private void SetImageFromResult(ServiceResult result, UIEntityTableViewCell <TEntity> cell)
{
if (cell != null)
{
if (result.ResultCode == ServiceResultCode.Success)
{
UIImage image = this.TryGetImageForCell(cell);
if (image == null)
{
// is it possible the image was automatically removed from the cache in such a short period of time?
throw new InvalidOperationException("An image was not found in the cache.");
}
cell.SetImage(image);
}
else
{
UIImage errorImage =
result.ResultCode == ServiceResultCode.NetworkUnavailable
? this.GetDisconnectedImage()
: this.GetImageDownloadFailedImage(result);
UIViewContentMode contentMode = UIViewContentMode.Center;
UIImageView imageView = cell.GetImageView();
if (errorImage != null &&
(errorImage.Size.Width > imageView.Bounds.Width ||
errorImage.Size.Height > imageView.Bounds.Height))
{
contentMode = UIViewContentMode.ScaleAspectFit;
}
cell.SetImage(errorImage, contentMode);
}
cell.MarkImageDownloadComplete(result.ResultCode == ServiceResultCode.Success);
}
}
/// <summary>
/// Occurs when a row has been deselected.
/// </summary>
/// <param name="cell">The cell that was deselected.</param>
protected virtual void OnRowDeselected(UIEntityTableViewCell <TEntity> cell)
{
}