private async Task <bool> NavigationOrchestratorAsync(Type page, object parameter, NavigationMode mode, Func <bool> navigate)
{
using (var locker = await LockAsync.Create(navigationLock))
{
DebugWrite($"Page: {page}, Parameter: {parameter}, NavigationMode: {mode}");
if (page == null)
{
throw new ArgumentNullException(nameof(page));
}
if (navigate == null)
{
throw new ArgumentNullException(nameof(navigate));
}
// this cannot be used for duplicate navigation, except for refresh
if (!Equals(mode, NavigationMode.Refresh))
{
if (Equals(page, CurrentPageType))
{
if (Equals(parameter, CurrentPageParam))
{
return(false);
}
}
}
// fetch current (which will become old)
var oldPage = FrameFacadeInternal.Content as Page;
var oldParameter = CurrentPageParam;
var oldViewModel = oldPage?.DataContext;
var oldPageState = await FrameFacadeInternal.GetPageStateAsync(oldPage?.GetType());
var fromInfo = new NavigationInfo(oldPage?.GetType(), oldParameter, oldPageState);
var toPageState = await FrameFacadeInternal.GetPageStateAsync(page?.GetType());
var toInfo = new NavigationInfo(page, parameter, toPageState);
// call oldViewModel.OnNavigatingFromAsync()
var viewmodelCancels = await Settings.ViewModelActionStrategy.NavigatingFromAsync((oldViewModel, false), fromInfo, toInfo, this);
if (viewmodelCancels)
{
return(false);
}
// raise Navigating event
RaiseNavigatingCancels(parameter, false, mode, toInfo, out var cancel);
if (cancel)
{
return(false);
}
// invoke navigate (however custom)
if (navigate.Invoke())
{
CurrentPageParam = parameter;
CurrentPageType = page;
}
else
{
return(false);
}
// fetch (current which is now new)
var newPage = FrameFacadeInternal.Content as Page;
var newViewModel = newPage?.DataContext;
// note: this has no value now, but it will
await Settings.ViewModelActionStrategy.NavigatingToAsync((newViewModel, mode, false), fromInfo, toInfo, this);
// raise Navigated event
RaiseNavigated(new NavigatedEventArgs()
{
Parameter = parameter,
NavigationMode = mode,
PageType = newPage?.GetType(),
});
// call oldViewModel.OnNavigatedFrom()
await Settings.ViewModelActionStrategy.NavigatedFromAsync((oldViewModel, false), fromInfo, toInfo, this);
// call newViewModel.ResolveForPage()
if (newViewModel == null)
{
newViewModel = ResolveViewModelForPage.Invoke(newPage);
newPage.DataContext = newViewModel;
}
// call newTemplate10ViewModel.Properties
if (newViewModel is ITemplate10ViewModel vm)
{
vm.NavigationService = this;
}
// call newViewModel.OnNavigatedToAsync()
await Settings.ViewModelActionStrategy.NavigatedToAsync((newViewModel, mode, false), fromInfo, toInfo, this);
// finally
return(true);
}
}
private async Task <bool> NavigationOrchestratorAsync(Type page, object parameter, NavigationMode mode, Func <bool> navigate)
{
if (!await navigationOrchestratorAsyncSemaphore.WaitAsync(TimeSpan.FromSeconds(10)))
{
throw new TimeoutException("Semaphore wait ellapsed");
}
// using (var locker = await LockAsync.Create(navigationLock))
try
{
DebugWrite($"Page: {page}, Parameter: {parameter}, NavigationMode: {mode}");
if (page == null)
{
throw new ArgumentNullException(nameof(page));
}
if (navigate == null)
{
throw new ArgumentNullException(nameof(navigate));
}
// this cannot be used for duplicate navigation, except for refresh
if (!Equals(mode, NavigationMode.Refresh))
{
if (Equals(page, CurrentPageType))
{
if (Equals(parameter, CurrentPageParam))
{
return(false);
}
}
}
// fetch current (which will become old)
var oldPage = FrameFacadeInternal.Content as Page;
var oldParameter = CurrentPageParam;
var oldViewModel = oldPage?.DataContext;
var oldPageState = await FrameFacadeInternal.GetPageStateAsync(oldPage?.GetType());
var from = new NavigationInfo(oldPage?.GetType(), oldParameter, oldPageState);
var newPageState = await FrameFacadeInternal.GetPageStateAsync(page?.GetType());
var to = new NavigationInfo(page, parameter, newPageState);
// call oldViewModel.OnNavigatingFromAsync()
var cancelled = await Settings.ViewModelActionStrategy.NavigatingFromAsync((oldViewModel, mode, false), from, to, this);
if (cancelled)
{
return(false);
}
// raise Navigating event
RaiseNavigatingCancels(parameter, false, mode, to, out var cancel);
if (cancel)
{
return(false);
}
// try to resolve the view-model before navigation
var newViewModel = default(object);
switch (mode)
{
case NavigationMode.New:
case NavigationMode.Refresh:
var strategy = Settings.ViewModelResolutionStrategy;
newViewModel = await strategy.ResolveViewModel(page);
if (newViewModel != null)
{
await Settings.ViewModelActionStrategy.NavigatingToAsync((newViewModel, mode, false), from, to, this);
}
break;
}
// navigate
var newPage = default(Page);
if (navigate.Invoke())
{
if ((newPage = FrameFacadeInternal.Content as Page) == null)
{
return(false);
}
CurrentPageParam = parameter;
CurrentPageType = page;
}
else
{
return(false);
}
// fetch current (which is now new)
if (newViewModel != null)
{
newPage.DataContext = newViewModel;
}
else if ((newViewModel = newPage?.DataContext) != null)
{
await Settings.ViewModelActionStrategy.NavigatingToAsync((newViewModel, mode, false), from, to, this);
}
// raise Navigated event
RaiseNavigated(new NavigatedEventArgs()
{
Parameter = parameter,
NavigationMode = mode,
PageType = newPage?.GetType(),
});
// call oldViewModel.OnNavigatedFrom()
await Settings.ViewModelActionStrategy.NavigatedFromAsync((oldViewModel, mode, false), from, to, this);
// call newTemplate10ViewModel.Properties
if (newViewModel is ITemplate10ViewModel vm)
{
vm.NavigationService = this;
}
// call newViewModel.OnNavigatedToAsync()
await Settings.ViewModelActionStrategy.NavigatedToAsync((newViewModel, mode, false), from, to, this);
// finally, all-good
return(true);
}
catch (Exception ex)
{
throw;
}
finally
{
navigationOrchestratorAsyncSemaphore.Release();
}
}