/// <summary>
/// Construct a TravelLog connected to a PivotViewer
/// </summary>
private TravelLog(PivotViewer pivotViewer, Uri initialCollectionUri)
{
m_pivotViewer = pivotViewer;
m_travelLog = new Dictionary<string, TravelLogEntry>();
m_currentTravelLogEntry = new TravelLogEntry(initialCollectionUri, string.Empty);
// Hook the events that are needed to implement travel log
m_pivotViewer.PropertyChanged += new PropertyChangedEventHandler(PivotViewer_PropertyChanged);
App.Current.Host.NavigationStateChanged += OnHostNavigationStateChanged;
}
/// <summary>
/// Handle navigation by using an existing travel log mapping, or creating a new one
/// </summary>
private void TravelLogNavigation(string oldNavigationState, string newNavigationState)
{
if (newNavigationState.StartsWith("/viewerStateKey/") || string.IsNullOrEmpty(newNavigationState))
{
TravelLogEntry newTravelLogEntry = null;
if (m_travelLog.TryGetValue(newNavigationState, out newTravelLogEntry)
&& (m_pivotViewer.CollectionUri != newTravelLogEntry.CollectionUri
|| m_pivotViewer.ViewerState != newTravelLogEntry.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
m_isNavigating = true;
m_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
m_pivotViewer.LoadCollection(newTravelLogEntry.CollectionUri.ToString(), newTravelLogEntry.ViewerState);
m_pivotViewer.CurrentItemId = newTravelLogEntry.CurrentItem;
// Build up a new current entry for the state that will be loaded
m_currentTravelLogEntry = new TravelLogEntry(newTravelLogEntry.CollectionUri, newTravelLogEntry.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 (newTravelLogEntry != null)
{
AddCurrentStateToTravelLog(oldNavigationState, m_pivotViewer.CurrentItemId);
m_pivotViewer.CurrentItemId = newTravelLogEntry.CurrentItem;
}
else
{
AddCurrentStateToTravelLog(oldNavigationState);
}
// Build up a new current entry for the existing current state
m_currentTravelLogEntry = new TravelLogEntry(m_pivotViewer.CollectionUri, m_pivotViewer.ViewerState);
}
}
}