how to get json data from api in listview paging

[waqas rauf]

i want to get data from web api in listview with paging. What i have done so far i dont see any problem in my code but i am getting null values in  Handle_OnDemandLoading

here is my code

 private FeaturedItemList products = new FeaturedItemList();  

        protected async void FeaturedList()
        {

   var httpClient = new HttpClient();
                      

                        var json = await httpClient.GetStringAsync("http://orangepotato.rjcpacking.com/index.php?route=api/login/getFeaturedProducts");


                        products = JsonConvert.DeserializeObject<FeaturedItemList>(json);
               
                        dataPager.Source = products.products;



        }  

void  Handle_OnDemandLoading(object sender, Syncfusion.SfDataGrid.XForms.DataPager.OnDemandLoadingEventArgs e)
        {
            var source= products.products.Skip(e.StartIndex).Take(e.PageSize);
            FeaturedlistView.ItemsSource = source.AsEnumerable();// here is i am getting null values but i am getting values in datapager.source
        }  

kindly need to resolove this issue asap

[Deivaselvan Y]

Hi Waqas, 

Thank you for contacting Syncfusion support.

 

We have checked the reported query from our side. You can deserialize and load the data into ItemsSource collection like below. We have attached the tested sample using SfDataPager and SfListView which fetches the data from respected API service using OnDemandLoading, please find the sample from below and code snippet for your reference.  

  

Sample Link : http://www.syncfusion.com/downloads/support/forum/143617/ze/ListViewSample1273666316  

  

  

In ViewModel  

public async System.Threading.Tasks.Task<ObservableCollection<Data>> RefreshDataAsync()  

{  

      Collection = new ObservableCollection<Data>();  

      RestUrl = "Api service link";  

      var uri = new Uri(RestUrl);  

      try  

      {  

          var response = await client.GetAsync(uri);  

  

          if (response.IsSuccessStatusCode)  

          {  

            var content = await response.Content.ReadAsStringAsync();  

            Items = JsonConvert.DeserializeObject<FullData>(content);  

  

            for (int i = 0; i < 5; i++)  

            {  

               var data = new Data()  

               {  

                 _Name = Items [i].Name,  

                 _Id=Items[i].Id  

               };  

               Collection.Add(data);  

             }  

             return Collection;  

           }  

        }  

}  

 

In Behavior.cs 

 

dataPager.OnDemandLoading += DataPager_OnDemandLoading; 

 

private void DataPager_OnDemandLoading(object sender, OnDemandLoadingEventArgs e) 

{ 

    Device.BeginInvokeOnMainThread(async () => { 

      await Task.Delay(100); 

      var source = viewModel.ItemsSource.Skip(e.StartIndex).Take(e.PageSize); 

      ListView.ItemsSource = source.ToList<Data>(); 

      dataPager.LoadDynamicItems(e.StartIndex, source); 

      dataPager.PagedSource.UseOnDemandPaging = true; 

    }); 

} 

  

Please let us know if you need any further assistance.  

  

Regards,  

Deivaselvan 

[waqas rauf]

sir the link u have send i have tried exactly same with the code but its not working. Here is my code this code absolutely work fine with android, but in ios data doesnt display but can pagination to next and previous.

 public partial class Home : ContentPage
    {  

 public Home ()
        {
            InitializeComponent ();

            FeaturedList();
          
            dataPager.OnDemandLoading += DataPager_OnDemandLoading;  

} 

        protected async void FeaturedList()
        {


            try
            {
                var connection = CrossConnectivity.Current.IsConnected;
                if (connection == true)
                {
                    try
                    {
                        //activity.IsRunning = true;
                        //activity.IsVisible = true;


                        var httpClient = new HttpClient();
                        

                        var json = await httpClient.GetStringAsync("http://orangepotato.rjcpacking.com/index.php?route=api/login/getFeaturedProducts");


                        products = JsonConvert.DeserializeObject<FeaturedItemList>(json);
                       
                       

                        foreach (var item in products.products)
                        {
                            products list = new products();
                            list.discount_percentage = item.discount_percentage;
                            list.name = item.name;
                            list.price = item.price;
                            list.special = item.special;
                            list.thumb = item.thumb;
                            if (item.special.ToString() == "0")
                            {
                                list.discount = "White";
                                list.price = item.price;
                            }
                            else
                            {
                                list.discount = "#f29d30";
                                list.price = item.special;
                            }
                            FeaturedFinalList.Add(list);

                        }

                        dataPager.Source = FeaturedFinalList;



                       

                    }
                    catch (Exception ex)
                    {

                        var exx = ex.Message;
                        await DisplayAlert("Alert", ex.Message, "Okay", "Cancel");
                    }
                    finally
                    {
                        

                    }
                }
                else
                {
                    await DisplayAlert("Message", "Please check your internet connection", "ok");

                }

            }
            catch (WebException ex)
            {

                var exx = ex.Message;
                await DisplayAlert("Message", ex.Message, "ok");
            }

        } 

 private void DataPager_OnDemandLoading(object sender, OnDemandLoadingEventArgs e)
        {
            Device.BeginInvokeOnMainThread(async () => {
                await Task.Delay(100);
                var source = FeaturedFinalList.Skip(e.StartIndex).Take(e.PageSize);
                FeaturedlistView.ItemsSource = source.ToList<products>();
                dataPager.LoadDynamicItems(e.StartIndex, source);
                dataPager.PagedSource.UseOnDemandPaging = true;
            });
        }  

}

[Dinesh Babu Yadav]

Hi Waqas, 

 

We recommend you to initialize the SfListView for each platform to render it. Please refer the following documentation for more reference. 

 

https://help.syncfusion.com/xamarin/sflistview/getting-started#launching-the-sflistview-on-each-platform 

 

Please let us know if you need any further assistance.   

   

Regards, 

Dinesh Babu Yadav 

 

[waqas rauf]

i have renderer listview in ios  and i found something strange, sometime it work fine on ios when i debug app again it disappear, but it doesnt happen with android. I really dont understand what is the issue.

[Dinesh Babu Yadav]

Hi Waqas, 

 

We suspect that the issue may occur at the application when the data is fetched from the server link. So, can you please check whether the collection is updated properly to Source parameter in the  “dataPager.LoadDynamicItems(e.StartIndex, source)” method while debugging the application and when page is navigated through data pager?.  

 

If you are still facing the issue, please share the video link and if possible replicate the issue by modifying the given sample in the previous update which would help us to analyze the issue better and update you an appropriate solution. 

 

Regards, 

Dinesh Babu Yadav