private PivotViewerHistory(PivotViewer pivotViewer, Uri initialCollectionUri)
{
_pivotViewer = pivotViewer;
_history = new Dictionary<string, PivotViewerHistoryEntry>();
_currentHistoryEntry = new PivotViewerHistoryEntry(initialCollectionUri, string.Empty);
_pivotViewer.PropertyChanged += OnPropertyChanged;
App.Current.Host.NavigationStateChanged += OnHostNavigationStateChanged;
}
private void PivotViewerNavigation(string oldNavigationState, string newNavigationState)
{
if (!newNavigationState.StartsWith("/viewerStateKey/") && !string.IsNullOrEmpty(newNavigationState))
return;
PivotViewerHistoryEntry newEntry = null;
if (_history.TryGetValue(newNavigationState, out newEntry)
&& (_pivotViewer.CollectionUri != newEntry.CollectionUri
|| _pivotViewer.ViewerState != newEntry.ViewerState))
{
// There is a mapping from the navigation state to a travel log entry, and the state in the travel log entry
// is different from the current PivotViewer state, so apply the travel log entry state to get the appropriate
// forward/back effect
_isNavigating = true;
_hasItemIdBeenUpdatedFromCollectionLoad = false;
// Before updating the ViewerState, update the mapping from navigation state to refer to the current ViewerState
AddCurrentStateToTravelLog(oldNavigationState);
// Load the collection and ViewerState in the travel log entry, and set the targeted focus item which will be focused
// once the new ViewerState has settled
_pivotViewer.LoadCollection(newEntry.CollectionUri.ToString(), newEntry.ViewerState);
_pivotViewer.CurrentItemId = newEntry.CurrentItem;
// Build up a new current entry for the state that will be loaded
_currentHistoryEntry = new PivotViewerHistoryEntry(newEntry.CollectionUri, newEntry.ViewerState);
}
else
{
// There is no mapping, or the state is the same as the existing state (for example, user moved from grid view
// to graph view, and back to grid view, then uses the travel log dropdown to back up two entries in one step,
// this should result in no state change to PivotViewer, except for possibly a current item change)
if (newEntry != null)
{
AddCurrentStateToTravelLog(oldNavigationState, _pivotViewer.CurrentItemId);
_pivotViewer.CurrentItemId = newEntry.CurrentItem;
}
else
AddCurrentStateToTravelLog(oldNavigationState);
// Build up a new current entry for the existing current state
_currentHistoryEntry = new PivotViewerHistoryEntry(_pivotViewer.CollectionUri, _pivotViewer.ViewerState);
}
}
