private async void ScrollViewer_ViewChanged(object sender, ScrollViewerViewChangedEventArgs e)
{
var scrollViewer = (ScrollViewer)sender;
if (scrollViewer.VerticalOffset < 0.001)
{
LoadingRing.IsActive = true;
LoadingRing.Visibility = Visibility.Visible;
var skip = viewModel.Messages.Count;
var item = viewModel.Messages.FirstOrDefault();
try
{
var request = new GetMessagesRequest
{
ChannelId = viewModel.SelectedChannel.Id
};
var result = await HttpApi.Channel.GetMessagesAsync(request, skip, 50, HttpApi.AuthToken);
for (var i = result.Count - 1; i >= 0; i--)
{
viewModel.Messages.Insert(0, result[i]);
}
MessageView.ScrollIntoView(item);
}
catch (ApiException ex)
{
await ex.ShowErrorDialog();
}
finally
{
LoadingRing.IsActive = false;
LoadingRing.Visibility = Visibility.Collapsed;
}
}
}
private async void ViewModel_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
if (e.PropertyName == "Messages")
{
await Task.Delay(100);
MessageView.ScrollIntoView(viewModel.Messages.LastOrDefault());
}
}
public ChatPage()
{
InitializeComponent();
viewModel = (ChatViewModel)DataContext;
viewModel.PropertyChanged += ViewModel_PropertyChanged;
viewModel.Recieved = async message =>
{
await Task.Delay(100);
MessageView.ScrollIntoView(viewModel.Messages.LastOrDefault());
};
MessageView.Loaded += (s, a) =>
{
var scrollViewer = GetScrollViewer(MessageView);
scrollViewer.ViewChanged += ScrollViewer_ViewChanged;
};
SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility = AppViewBackButtonVisibility.Visible;
}
