private async Task <INavigationResult> NavigateAsync(
NavigationQueue queue,
NavigationTransitionInfo infoOverride)
{
Debug.WriteLine($"{nameof(FrameFacade)}.{nameof(NavigateAsync)}({queue})");
// clear stack, if requested
if (queue.ClearBackStack)
{
_frame.SetNavigationState(new Frame().GetNavigationState());
}
// iterate through queue
while (queue.Count > 0)
{
var pageNavinfo = queue.Dequeue();
var result = await NavigateAsync(
pageNavInfo : pageNavinfo,
infoOverride : infoOverride);
// do not continue on failure
if (!result.Success)
{
return(result);
}
}
// finally
return(NavigationResult.Successful());
}
public async Task <INavigationResult> GoForwardAsync()
{
if (!CanGoForward())
{
return(NavigationResult.Failure($"{nameof(CanGoForward)} is false."));
}
return(await OrchestrateAsync(
parameters : null,
mode : Prism.Navigation.NavigationMode.Forward,
navigate : async() =>
{
_frame.GoForward();
return true;
}));
}
public async Task <INavigationResult> GoBackAsync(INavigationParameters parameters,
NavigationTransitionInfo infoOverride)
{
if (!CanGoBack())
{
return(NavigationResult.Failure($"{nameof(CanGoBack)} is false."));
}
return(await OrchestrateAsync(
parameters : parameters,
mode : Prism.Navigation.NavigationMode.Back,
navigate : async() =>
{
_frame.GoBack(infoOverride);
return true;
}));
}
private async Task <INavigationResult> OrchestrateAsync(
INavigationParameters parameters,
Prism.Navigation.NavigationMode mode,
Func <Task <bool> > navigate)
{
// setup default parameters
parameters = CreateDefaultParameters(parameters, mode);
// pre-events
var old_vm = (_frame.Content as Page)?.DataContext;
if (old_vm == null)
{
Debug.WriteLine($"[From]View-Model is null.");
}
else if (!await CanNavigateAsync(parameters, old_vm))
{
return(NavigationResult.Failure($"[From]{old_vm}.CanNavigateAsync returned false."));
}
else if (!CanNavigate(parameters, old_vm))
{
return(NavigationResult.Failure($"[From]{old_vm}.CanNavigate returned false."));
}
// navigate
var success = await NavigateFrameAsync(navigate);
Debug.WriteLine($"{nameof(FrameFacade)}.{nameof(OrchestrateAsync)}.NavigateFrameAsync() returned {success}.");
if (!success)
{
return(NavigationResult.Failure("NavigateFrameAsync() returned false."));
}
var new_page = _frame.Content as Page;
if (new_page == null)
{
throw new Exception("There is no new page in Frame after Navigate.");
}
// post-events
if (old_vm != null)
{
OnNavigatedFrom(parameters, old_vm);
}
var new_vm = new_page?.DataContext;
if (new_vm == null)
{
if (Central.Registry.TryGetRegistration(_frame.CurrentSourcePageType, out var info) && info.ViewModel != null)
{
new_page.DataContext = new_vm = Central.Container.Resolve(info.ViewModel);
}
}
if (new_vm == null)
{
Debug.WriteLine($"[To]View-Model is null.");
}
else
{
await OnNavigatedToAsync(parameters, new_vm);
OnNavigatingTo(parameters, new_vm);
OnNavigatedTo(parameters, new_vm);
}
// refresh-bindings
BindingUtilities.UpdateBindings(new_page);
// finally
return(NavigationResult.Successful());
}