Xamarin.forms 下载数据后刷新轮播视图

Question

I am learning xamarin,

I am trying to refresh my carouselView every time I download data.

The data are downloaded correctly, but the problem is when I download new data and I want to swap on my carrouselView to see my new data after a previous data download.

The carousel 'move' and positionning me at my previous position (index) even if I want to be position on position (index) 0 at every data download

How can I refresh correctly my carouselview?

Here is my code cs:

try
        {

        // trying to refresh by renitializing my carouselView
        Device.BeginInvokeOnMainThread(() =>
        {
            NewsList.Position = 0;
            NewsList.ItemsSource = null;
          
           
        });

            
        // Perform the Web request and get the response
        HttpWebResponse response = (HttpWebResponse)request.GetResponseAsync().Result;

        // Data Downloaded
        string json = new StreamReader(response.GetResponseStream()).ReadToEnd();
        JObject joResponse = JObject.Parse(json);
        JArray MyJsonResult = (JArray)joResponse["value"];



          List<NewsModel> newsObj = new List<NewsModel>();
             
                foreach (var j in MyJsonResult)
            {

                    joResponse2 = JObject.Parse(j.ToString());

                    if (joResponse2["image"]!= null)
                    {
                        

                        var news = new NewsModel();
                        news.NewsName = GetFewWordsSentence(joResponse2["name"].ToString()) ;
                        news.NewsDate = joResponse2["datePublished"].ToString();
                        news.NewsImageUrl = joResponse2["image"]["contentUrl"].ToString(); 
                        newsObj.Add(news);

                     // feed my carouselView in the loop for performance
                       // I have already try, to put this line out of the loop but it is not refresh correctly also
                    Device.BeginInvokeOnMainThread(() =>
                    {
                        NewsList.ItemsSource = newsObj;

                   });


                }
               
                }

                    
    }


    catch (Exception e)
    {
        Console.Error.WriteLine(@"ERROR {0}", e.Message);

    }

Thanks in advance

Answer 1

The carousel 'move' and positionning me at my previous position (index) even if I want to be position on position (index) 0 at every data download

According to your description, you download data and display CarouselView, then you swap item for CarouselView in any position. You want to display new data and go to position 0 when download data again, am I right?

If yes, I suggest you can use observablecollection to replace List firstly, it implement INotifyPropertychanged interface to notify when data update.

  public ObservableCollection<NewsModel> newsObj { get; set; }

then clear data when you download data again,

 newsObj.Clear();

Using ScrollTo scrolls the item at the specified index into view.

 Device.BeginInvokeOnMainThread(()=>
        {
            newsList.ScrollTo(0);
        }
        ) ;