/// <summary>
/// Standard listbox method to recycle items
/// </summary>
/// <param name="element">The LazyListBoxItem being recycled</param>
/// <param name="item">The old item that's about to get thrown out</param>
protected override void ClearContainerForItemOverride(DependencyObject element, object item)
{
LazyListBoxItem listBoxItem = (element as LazyListBoxItem);
#if false
// Enable this if you are having issues with recycling
Debug.WriteLine("Clearing container " + listBoxItem.Id + " for item " + item.ToString());
#endif
// If it's a special ILazyDataItem, tell it to unload
ILazyDataItem lazyItem = item as ILazyDataItem;
if (lazyItem != null)
{
lazyItem.GoToState(LazyDataLoadState.Unloaded);
}
base.ClearContainerForItemOverride(element, item);
}
/// <summary>
/// Standard method for recycling containers
/// </summary>
/// <param name="element">The LazyListBoxItem being prepared for a new object</param>
/// <param name="item">The item that's about to be put into the container</param>
protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
{
LazyListBoxItem listBoxItem = (element as LazyListBoxItem);
#if false
// Enable this if you are having issues with container recycling
Debug.WriteLine("Preparing container " + listBoxItem.Id + " for item " + item.ToString());
#endif
base.PrepareContainerForItemOverride(element, item);
// If it's a special ILazyDataItem, tell it to go to the minimum loaded state
ILazyDataItem lazyItem = item as ILazyDataItem;
if (lazyItem != null && lazyItem.CurrentState == LazyDataLoadState.Unloaded)
{
lazyItem.GoToState(LazyDataLoadState.Minimum);
}
// Reset to the basic item template
listBoxItem.ContentTemplate = ItemTemplate;
}
/// <summary>
/// Forces the item to be visible or invisible
/// </summary>
/// <param name="isVisible">True if the item is visible, false otherwise</param>
/// <param name="currentSnapshotVersion">Version information used for cache purposes</param>
internal void SetIsVisible(bool isVisible, int currentSnapshotVersion)
{
// We have special behaviour if the item is an ILazyDataItem
ILazyDataItem lazyItem = DataContext as ILazyDataItem;
cachedIsVisible = isVisible;
visibleSnapshotVersion = currentSnapshotVersion;
if (isVisible)
{
// If it's a special item, tell it to change states based on its current state
if (lazyItem != null)
{
LazyDataLoadState currentState = lazyItem.CurrentState;
// It was cached, so tell it to re-load
if (currentState == LazyDataLoadState.Cached)
{
lazyItem.GoToState(LazyDataLoadState.Reloading);
}
// It was loading and we asked it to pause; unpause it
else if (currentState == LazyDataLoadState.Loading || currentState == LazyDataLoadState.Reloading)
{
if (lazyItem.IsPaused)
{
lazyItem.Unpause();
}
}
// Otherwise, tell it to load unless it is already loading
else if (currentState != LazyDataLoadState.Loaded)
{
lazyItem.GoToState(LazyDataLoadState.Loading);
}
}
// Set the loaded item template, if it exists
if (Owner.LoadedItemTemplate != null)
{
ContentTemplate = Owner.LoadedItemTemplate;
}
}
else
{
bool alreadyResetTemplate = false;
// If it's a special item, tell it to change state
if (lazyItem != null)
{
// if the slow items are already loaded, switch to the cached template (vs the default template)
if (lazyItem.CurrentState == LazyDataLoadState.Loaded)
{
lazyItem.GoToState(LazyDataLoadState.Cached);
if (Owner.CachedItemTemplate != null)
{
ContentTemplate = Owner.CachedItemTemplate;
alreadyResetTemplate = true;
}
}
}
// If we didn't set it to the CachedItemTemplate, then reset to the ItemTemplate
if (alreadyResetTemplate != true && Owner.Template != null)
{
ContentTemplate = Owner.ItemTemplate;
}
}
}
