protected virtual void OnNavigating(NavigatingCancelEventArgsBase args)
{
if (args.Context.Contains(IgnoreNavigatingConstant))
{
return;
}
var context = CreateContextNavigateFrom(args);
if (context == null)
{
return;
}
args.Cancel = true;
var navigateTask = !args.IsCancelable
? Empty.TrueTask
: NavigationDispatcher.OnNavigatingAsync(context);
navigateTask.TryExecuteSynchronously(task =>
{
if (!task.IsCanceled && task.IsFaulted)
{
TryCompleteNavigationTask(args.Context, false);
NavigationDispatcher.OnNavigationFailed(context, task.Exception);
return;
}
if (task.IsCanceled || !task.Result)
{
TryCompleteNavigationTask(args.Context, false);
if (!context.NavigationMode.IsClose())
{
NavigationDispatcher.OnNavigationCanceled(context);
}
return;
}
ThreadManager.Invoke(ExecutionMode.AsynchronousOnUiThread, this, context, args, (@this, ctx, e) =>
{
e.Context.AddOrUpdate(IgnoreNavigatingConstant, null);
@this.Renavigate(ctx, e);
});
});
}
private Task <bool> TryCloseRootAsync(IViewModel viewModel, IDataContext context)
{
if (viewModel == null || !viewModel.Settings.State.Contains(IsRootConstant) || viewModel.Settings.Metadata.Contains(IsClosed))
{
return(null);
}
var currentView = viewModel.GetCurrentView <object>();
var backButtonAction = XamarinFormsToolkitExtensions.SendBackButtonPressed?.Invoke(currentView);
if (backButtonAction == null)
{
return(null);
}
var navigationContext = new NavigationContext(NavigationType.Page, NavigationMode.Back, viewModel, null, this, context);
var task = NavigationDispatcher.OnNavigatingAsync(navigationContext);
if (task.IsCompleted)
{
if (task.Result)
{
viewModel.Settings.Metadata.AddOrUpdate(IsClosed, null);
_hasRootPage = false;
NavigationDispatcher.OnNavigated(navigationContext);
}
return(task);
}
return(task.TryExecuteSynchronously(t =>
{
if (!t.Result)
{
return false;
}
_hasRootPage = false;
viewModel.Settings.Metadata.AddOrUpdate(IsClosed, null);
backButtonAction();
NavigationDispatcher.OnNavigated(navigationContext);
return true;
}));
}
private Task <bool> CloseViewModel(INavigationDispatcher navigationDispatcher, IViewModel viewModel, IDataContext ctx)
{
if (!(viewModel is TViewModel))
{
return(Empty.FalseTask);
}
var removeCtx = new NavigationContext(NavigationType.Tab, NavigationMode.Remove, viewModel, null, this, ctx);
return(NavigationDispatcher
.OnNavigatingAsync(removeCtx)
.TryExecuteSynchronously(task =>
{
if (task.Result)
{
_lastRemoveContext = removeCtx;
return ItemsSource.Remove((TViewModel)viewModel);
}
return false;
}));
}