Xamarin Forms: how not reload ListView when pop back

Question

In Xamarin Forms i have a ListView and the following method in Code Behind:

    protected async override void OnAppearing()
    {
        base.OnAppearing();

        events.ItemsSource = await App.ServiceManager.GetStream();
    }

where

events

is my ListView and fetch data from rest webservice.

When i select an item in the ListView i push a detail page. The problem is that when i pop back to the ListView, the method OnAppearing() is called and make the remote call again.

Instead i'd like that the scroll start from the previous position (before that i push a new page): how can do that?

Move the logic to ViewModel and create a single instance of it - for example. — EvZ
– EvZ, Commented Mar 8, 2017 at 19:15

Alessandro Caliaro · Accepted Answer · 2017-03-08 17:17:51Z

1

I think you can simply use a

bool isFirstAppearing = true;

protected async override void OnAppearing()
{
    base.OnAppearing();

    if(isFirstAppearing) {
         isFirstAppearing = false;
         events.ItemsSource = await App.ServiceManager.GetStream();
    }
}

answered Mar 8, 2017 at 17:17

Alessandro Caliaro

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1 Comment

KalleP Over a year ago

This does not work if you have a command to go back to that page. @Alessandro Caliaro

Kyle · Accepted Answer · 2017-03-09 21:15:36Z

0

You can either do a check if its already been loaded, as alessandro Caliaros answer suggests, or an alternative if you want to get fresh data but still be scrolled in the same position, you can add code in onappearing to set the scroll position to be the same as it was before:

var currentYPosition = _scrollView.ScrollY;
await _scrollView.ScrollToAsync(_scrollView.ScrollX, currentYPosition, true);

answered Mar 9, 2017 at 21:15

Kyle

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