private bool Navigate(Screen screen, bool isBackNavigation, object parameter = null)
{
bool overlayed = false;
// Navigation ankündigen und prüfen, ob das ok geht.
NavigationEventArgs args = new NavigationEventArgs()
{
IsBackNavigation = isBackNavigation,
Parameter = parameter,
Screen = screen,
};
// Schritt 1: Vorherigen Screen "abmelden"
if (ActiveScreen != null)
{
overlayed = activeScreen.IsOverlay;
ActiveScreen.InternalNavigateFrom(args);
// Abbruch durch Screen eingeleitet
if (args.Cancel) { return false; }
// Screen deaktivieren
ActiveScreen.Enabled = false;
// Spezialfall (aktueller Screen nicht in History, neuer Screen Overlay)
if (!ActiveScreen.InHistory && screen != null && screen.IsOverlay)
historyStack.Insert(0, ActiveScreen);
// Ausblenden, wenn der neue Screen nicht gerade ein Overlay ist
if (screen == null || !screen.IsOverlay)
{
// Überblenden, falls erforderlich
if (NavigateFromTransition != null)
{
ActiveScreen.Alpha = 1f;
var trans = NavigateFromTransition.Clone(ActiveScreen);
trans.Finished += (s, e) =>
{
ScreenTarget.Controls.Remove(e);
};
activeScreen.StartTransition(trans);
}
else
{
ScreenTarget.Controls.Remove(ActiveScreen);
}
}
// NavigatedFrom-Event aufrufen
args.Cancel = false;
args.Handled = false;
args.IsBackNavigation = isBackNavigation;
args.Screen = screen;
ActiveScreen.InternalNavigatedFrom(args);
// entfernen
args.Screen = ActiveScreen;
ActiveScreen = null;
}
else args.Screen = null;
// Schritt 2: zum neuen Screen navigieren
if (screen != null)
{
// NavigateTo-Event aufrufen
args.Cancel = false;
args.Handled = false;
args.IsBackNavigation = isBackNavigation;
screen.InternalNavigateTo(args);
// Neuen Screen einhängen
if (historyStack.Contains(screen))
historyStack.Remove(screen);
if (screen.InHistory)
historyStack.Insert(0, screen);
if (!overlayed)
{
if (NavigateToTransition != null)
{
screen.Alpha = 0f;
var trans = NavigateToTransition.Clone(screen);
screen.StartTransition(trans);
}
ScreenTarget.Controls.Add(screen);
}
ActiveScreen = screen;
ActiveScreen.Enabled = true;
// Navigate-Events aufrufen
args.Cancel = false;
args.Handled = false;
args.IsBackNavigation = isBackNavigation;
ActiveScreen.InternalNavigatedTo(args);
}
return true;
}
public bool NavigateToScreen(Screen screen, object parameter = null)
{
return Navigate(screen, false, parameter);
}