Construction of Spark machine learning environment

In recent days, I have been loading and refreshing on the research. However, there are always so many tricks. In xamarin.forms, list comes with an attribute that doesn't pull up and load (didn't they think about what would happen when they encapsulated methods? (complain instead of complaining, the problem always has to be solved.

Since I don't have one, I'll write one myself.

Train of thought

Here's what I'm thinking.

What is pull-up refresh, that is to say, on the current page, when I see the last item, I need to load some new data, so can I write one, as soon as the last item appears, we will refresh the latest data?

1 public class InfiniteListView: ListView 2 {3 public static readonly BindableProperty LoadMoreCommandProperty = BindableProperty.Create (nameof (LoadMoreCommand), typeof (ICommand), typeof (InfiniteListView)); 4 public static readonly BindableProperty CanLoadMoreProperty = BindableProperty.Create (nameof (CanLoadMore), typeof (bool), typeof (InfiniteListView), true); 5 6 public ICommand LoadMoreCommand 7 {8 get {return (ICommand) GetValue (LoadMoreCommandProperty);} 9 set {SetValue (LoadMoreCommandProperty, value) } 10} 11 12 public bool CanLoadMore13 {14 get15 {16 return (bool) GetValue (CanLoadMoreProperty); 17} 18 set19 {20 SetValue (CanLoadMoreProperty, value) 21} 22} 23 24 public InfiniteListView () 25 {26 ItemAppearing + = InfiniteListView_ItemAppearing;27} 28 29 private void InfiniteListView_ItemAppearing (object sender, ItemVisibilityEventArgs e) 30 {31 if (! CanLoadMore) 32 {33 return;34} 35 var items = ItemsSource as IList 36 37 if (items! = null & & e.Item = = items [items.Count-1]) 38 {39 if (LoadMoreCommand! = null & & LoadMoreCommand.CanExecute (null)) 40 LoadMoreCommand.Execute (null); 41} 42} 43}

Let's inherit listview to implement its ItemAppearing method, and then determine again and again whether there is the last item in the method (to be honest, I don't know if this is good for the program, but now I just want to implement it), and execute the binding method as soon as the last item appears.

In page binding, you need to

So . . Is it really very simple?

After a brief test, a problem was found. That is, my list data, there are grouping, there may be multiple list in a list, so isn't the last item always the outermost data? I changed the method simply.