protected override async Task InnerNavigateBack(NavigationStackEntry entryToRemove, NavigationStackEntry activeEntry)
{
// When this flag is true, the Frame already navigated back (e.g. using the back button),
// so we don't need to ask the Frame to navigate back. The only thing we need to make
// sure is to reset the DataContext of the view.
if (!_isProcessingFrameInitiatedBack)
{
await Dispatcher.RunTaskAsync(CoreDispatcherPriority.High, UIBack);
if (!(entryToRemove.Request.SuppressTransitions ?? false))
{
// There's no way to know when the animation ends. So, we assume it runs for 250ms.
await Task.Delay(millisecondsDelay : 250);
}
}
_ = Dispatcher.RunAsync(CoreDispatcherPriority.Low, () => UIResetDataContext(entryToRemove));
async Task UIBack()
{
try
{
var overrideInfo = entryToRemove.Request.SuppressTransitions ?? false
? (NavigationTransitionInfo) new SuppressNavigationTransitionInfo()
: (NavigationTransitionInfo) new SlideNavigationTransitionInfo()
{
Effect = SlideNavigationTransitionEffect.FromRight
};
var result = await WaitForNavigationResult(() => _frame.GoBack(overrideInfo));
#if NETFX_CORE
// On Windows, Frame re-creates a new Page instance for every navigation (whether through Navigate or GoBack),
// unless NavigationCacheMode is set to Required (in which case a single Page instance is recycled).
if (result.Content != activeEntry.View)
{
// A new Page instance has been created and set as the content of the Frame.
// However, this new instance doesn't reflect the state or DataContext of the actual previous page.
// Therefore, we replace it with the previous page instance we saved earlier.
_frame.Content = activeEntry.View;
}
#endif
}
catch (Exception e)
{
if (_logger.IsEnabled(LogLevel.Error))
{
_logger.LogError($"Failed frame navigate back.", e);
}
}
}
}
protected override Task InnerNavigateBack(NavigationStackEntry entryToRemove, NavigationStackEntry activeEntry)
{
// Don't do anything.
return(Task.CompletedTask);
}