public void OnNavigated(PageIndex pageIndex, bool isFailedBackNav)
{
var stackIdentifier = pageIndex.GetAssociatedStack();
var stackCount = _stacks[stackIdentifier].Count;
var message = new NavigationStackUpdateMessage
{
NavigationStack = stackIdentifier,
CanGoBack = stackCount > 0,
NavigatedBackToEmpty = stackCount <= 0 && isFailedBackNav
};
Messenger.Default.Send(message);
}
private void OnNavigationStackUpdateMessage(NavigationStackUpdateMessage message)
{
if (message.NavigationStack == NavigationStack.OffStack)
{
if (message.NavigatedBackToEmpty)
{
OffFrame.Visibility = Visibility.Collapsed;
_offFrameWidthWhenLastHidden = OffFrameGridColumn.Width.Value;
OffFrameGridColumn.Width = new GridLength(0);
App.NavigationManager.Reset(PageIndex.OffStackIdentifier);
}
else
{
if (OffFrame.Visibility == Visibility.Collapsed)
{
OffFrame.Visibility = Visibility.Visible;
if (!_hasOffFrameBeenShown)
{
OffFrameGridColumn.Width = new GridLength(600);
_hasOffFrameBeenShown = true;
}
else
{
OffFrameGridColumn.Width = new GridLength(_offFrameWidthWhenLastHidden);
}
}
if (message.CanGoBack)
{
OffBackNavButton.Visibility = Visibility.Visible;
}
else
{
OffBackNavButton.Visibility = Visibility.Collapsed;
}
}
}
else
{
NavigationView.IsBackEnabled = message.CanGoBack;
}
}
