/// <summary>
/// Called when the value of the
/// <see cref="P:System.Windows.Controls.ContentControl.Content"/>
/// property changes.
/// </summary>
/// <param name="oldContent">The old <see cref="T:System.Object"/>.</param>
/// <param name="newContent">The new <see cref="T:System.Object"/>.</param>
protected override void OnContentChanged(object oldContent, object newContent)
{
base.OnContentChanged(oldContent, newContent);
UIElement oldElement = oldContent as UIElement;
UIElement newElement = newContent as UIElement;
if (_firstContentPresenter == null || _secondContentPresenter == null || newElement == null)
{
return;
}
if (_useFirstAsNew)
{
_newContentPresenter = _firstContentPresenter;
_oldContentPresenter = _secondContentPresenter;
}
else
{
_newContentPresenter = _secondContentPresenter;
_oldContentPresenter = _firstContentPresenter;
}
_useFirstAsNew = !_useFirstAsNew;
NavigationOutTransition navigationOutTransition = null;
NavigationInTransition navigationInTransition = null;
ITransition oldTransition = null;
ITransition newTransition = null;
if (oldElement != null)
{
navigationOutTransition = TransitionService.GetNavigationOutTransition(oldElement);
TransitionElement oldTransitionElement = null;
if (navigationOutTransition != null)
{
oldTransitionElement = _isForwardNavigation ? navigationOutTransition.Forward : navigationOutTransition.Backward;
}
if (oldTransitionElement != null)
{
oldTransition = oldTransitionElement.GetTransition(oldElement);
_oldContentPresenter.CacheMode = new BitmapCache();
_oldContentPresenter.IsHitTestVisible = false;
}
}
if (newElement != null)
{
navigationInTransition = TransitionService.GetNavigationInTransition(newElement);
TransitionElement newTransitionElement = null;
if (navigationInTransition != null)
{
newTransitionElement = _isForwardNavigation ? navigationInTransition.Forward : navigationInTransition.Backward;
}
if (newTransitionElement != null)
{
newElement.UpdateLayout();
newTransition = newTransitionElement.GetTransition(newElement);
_newContentPresenter.CacheMode = new BitmapCache();
_newContentPresenter.IsHitTestVisible = false;
}
}
_newContentPresenter.Opacity = 0;
_newContentPresenter.Visibility = Visibility.Visible;
_newContentPresenter.Content = newElement;
_oldContentPresenter.Opacity = 1;
_oldContentPresenter.Visibility = Visibility.Visible;
_oldContentPresenter.Content = oldElement;
if (oldTransition != null)
{
if (oldTransition.GetCurrentState() != ClockState.Stopped)
{
oldTransition.Stop();
}
oldTransition.Completed += delegate
{
oldTransition.Stop();
_oldContentPresenter.CacheMode = null;
_oldContentPresenter.IsHitTestVisible = true;
if (navigationOutTransition != null)
{
navigationOutTransition.OnEndTransition();
}
TransitionNewElement(newTransition, navigationInTransition);
};
Dispatcher.BeginInvoke(delegate
{
Dispatcher.BeginInvoke(delegate
{
if (navigationOutTransition != null)
{
navigationOutTransition.OnBeginTransition();
}
oldTransition.Begin();
});
});
}
else
{
TransitionNewElement(newTransition, navigationInTransition);
}
}