Xamarin Forms: How to detect the scrollview(or expander) end or top reached?

Question

I need to load more data when scrollview reaches the end or top. I found the same thread over here, but on that, I didn't understand what is MyScrollView.

private void OnScrolled(object sender, ScrolledEventArgs e)
{
    MyScrollView scrollView = sender as MyScrollView;
    double scrollingSpace = scrollView.ContentSize.Height - scrollView.Height;

    if (scrollingSpace <= e.ScrollY)
    {
       //reached end
    }
}

I implemented the same in ListView using the ItemAppearing event. But currently, I am using Expander on the UI to display data. Is there any same kind of event for the expander to reach the end and beginning? The expander is inside of a scrollview, that's why I started researching about the scrollview end event.

Help me to find a way to trigger some kind of event when scrollview reaches end or beginning?

Answer 1

Like I mentioned in the question I have implemented the same feature in ListView using the ItemAppearing event. But in this case, my data is a list of items inside another list. That's why I forced to use the Expander component to display the data on the UI.

At the same time, I need to load more items when the Expander bottom reaches. But Expander doesn't provide the related event because it is not a scrollable control. So that I tried to find out an event for the ScrollView component. But no luck for that also.

Finally, I decided to change the data to a single list from a list inside another list. I have converted that using some for loops and now the data is suitable for ListView. And I have implemented the load more feature using the ItemAppearing event.

Thanks @JarvanZhang

Answer 2

Hello,​

Welcome to our Microsoft Q&A platform!

Is there any same kind of event for the expander to reach the end and beginning?

Expander doesn't provide the related event because it self is not a scrollable control.

I found the same thread over here, but on that, I didn't understand what is MyScrollView.

In you posted link, Bruno may use a custom ScrollView in his project. You could just change the 'MyScrollView' to ScrollView as below:

   private void ScrollView_Scrolled(object sender, ScrolledEventArgs e)  
   {  
       var scrollView = sender as ScrollView;  
       double scrollingSpace = scrollView.ContentSize.Height - scrollView.Height;  
     
       if (scrollingSpace > e.ScrollY)  
           return;  
     
       //do the work  
       //the scrollView has scrolled to the last item  
   }  

Check this link: https://stackoverflow.com/a/57558768/11083277

Best Regards,

Jarvan Zhang

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