RefreshView's ActivityIndicator does not animate on first refresh

Question

I have a RefreshView in a page. I want the data to refresh the first time it is shown, so I have this:

protected override void OnAppearing()
{
    if(!_hasRefreshedFirstTime) {
        _hasRefreshedFirstTime = true;
        TypedContext.IsRefreshing = true;
    }
}

And in my view model the refresh command is the following, with Refresh = new AsyncCommand(DoRefresh, onException: exceptionHandler);:

public IAsyncCommand Refresh { get; }

private async Task DoRefresh()
{
    IsRefreshing = true;
    _ = await DataManager.RefreshOrderHistoryAsync();
    IsRefreshing = false;
}

This works, but this first time it is refreshing the ActivityIndicator is frozen. Interestingly, after that, if I pull to refresh, the indicator animates correctly.

My question is, why in the indicator not animated correctly and how can I fix that?

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

Is TypedContext.IsRefreshing = true; a static value? If so, please do not use this way to change the loading operation.

I use the official demo. Here is running screenshot. It is running normally.

You can Add a new method like DoRefresh method. Keep the IsRefreshing property, but achieve the IsRefreshing property with INotifyPropertyChanged interface, here is code about MainPageViewModel.cs.

   using System;  
   using System.Collections.Generic;  
   using System.Collections.ObjectModel;  
   using System.ComponentModel;  
   using System.Runtime.CompilerServices;  
   using System.Text;  
   using System.Threading.Tasks;  
   using System.Windows.Input;  
   using Xamarin.Forms;  
     
   namespace App110  
   {  
       public class Item  
       {  
           public string Name { get; set; }  
           public Color Color { get; set; }  
       }  
       public class MainPageViewModel : INotifyPropertyChanged  
       {  
           const int RefreshDuration = 2;  
           int itemNumber = 1;  
           readonly Random random;  
            bool isRefreshing;  
     
           public  bool IsRefreshing  
           {  
               get { return isRefreshing; }  
               set  
               {  
                   isRefreshing = value;  
                   OnPropertyChanged();  
               }  
           }  
     
           public ObservableCollection<Item> Items { get; private set; }  
     
           public ICommand RefreshCommand => new Command(async () => await DoRefresh());  
     
           public MainPageViewModel()  
           {  
               random = new Random();  
               Items = new ObservableCollection<Item>();  
              
           }  
     
           void AddItems()  
           {  
               
               for (int i = 0; i < 3; i++)  
               {  
                   Items.Add(new Item  
                   {  
                       Color = Color.FromRgb(random.Next(0, 255), random.Next(0, 255), random.Next(0, 255)),  
                       Name = $"Item {itemNumber++}"  
                   });  
               }  
     
               
           }  
       
           public async  void RefreshItemsAtFirstTimeAsync()  
           {  
               IsRefreshing = true;  
                
     
           }  
     
     
           public async Task DoRefresh()  
           {  
              
               IsRefreshing = true;  
     
               //add your loading code  
               await Task.Delay(TimeSpan.FromSeconds(RefreshDuration));  
               AddItems();  
               IsRefreshing = false;  
           }  
     
           #region INotifyPropertyChanged  
     
           public event PropertyChangedEventHandler PropertyChanged;  
     
           void OnPropertyChanged([CallerMemberName] string propertyName = null)  
           {  
               PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));  
           }  
     
           #endregion  
       }  
   }  

Then add class of bindingContext in the background code. You can execute the DoRefresh() method directly in OnAppearing method.

   public partial class MainPage : ContentPage  
       {  
           private  bool _hasRefreshedFirstTime;  
     
          
           MainPageViewModel mainPageViewModel;  
           public MainPage()  
           {  
               _hasRefreshedFirstTime = false;  
               mainPageViewModel =new MainPageViewModel();  
     
               BindingContext = mainPageViewModel;  
               InitializeComponent();  
           }  
           protected  override void OnAppearing()  
           {  
               base.OnAppearing();  
     
               if (!_hasRefreshedFirstTime)  
               {  
                   Console.WriteLine("===============================OnAppearing=====================");  
                   mainPageViewModel.RefreshItemsAtFirstTimeAsync();  
     
                   _hasRefreshedFirstTime = true;  
               }  
           }  
       }  

Best Regards,

Leon Lu

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