No change in visibility when changing the flag with binding

Question

I am having trouble setting the visibility of the ActivityIndicator.
When IsBusy = true in view model, the indicator is not visible in the view. How to solve it?

sample code in view model (MyViewModel):

 private bool _IsBusy;
    public bool IsBusy
    {
        get { return _IsBusy; }
        set { SetProperty(ref _IsBusy, value); }
    }

void MyDataChanged(object sender, ObjectChangeEventArgs e)
{            
    this.IsBusy = true;
    CommitChanges(); //takes aprox. 3 seconds
    this.IsBusy = false; 
}

My xaml in View:

    (...)
    xmlns:viewmodels="clr-namespace:Project.ViewModels" 
    x:DataType="viewmodels:MyViewModel"
    (...)
    <ActivityIndicator Grid.Row="1" Grid.Column="0" HeightRequest="100" WidthRequest="100" HorizontalOptions="Center" IsVisible="{Binding IsBusy}" IsRunning="True"/>
    (...)

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

You should move this.IsBusy = false; to the end of CommitChanges method. And I notice you used MVVM. I make a test with Button's Command. Here is MyViewModel

   public  class MyViewModel: BaseViewModel  
       {  
           private bool _IsBusy;  
           public bool IsBusy  
           {  
               get { return _IsBusy; }  
               set { SetProperty(ref _IsBusy, value); }  
           }  
           public ICommand TestCommand { protected set; get; }  
           public MyViewModel()  
           {  
               TestCommand = new Command(async (key) =>  
               {  
     
                   IsBusy = true;  
                   CommitChanges(); //takes aprox. 3 seconds  
                 //  IsBusy = false;  
               });  
           }  
     
           private async void CommitChanges()  
           {  
                
               await Task.Delay(3000);  
     
               IsBusy = false;  
           }  
       }  
     
       public abstract class BaseViewModel : INotifyPropertyChanged  
       {  
           public event PropertyChangedEventHandler PropertyChanged;  
     
           protected void OnPropertyChanged(  
                  [CallerMemberName] string propertyName = null)  
           {  
               PropertyChanged?.Invoke(  
                       this, new PropertyChangedEventArgs(propertyName));  
           }  
     
           protected void SetProperty<T>(ref T backingField,  
                 T value,  
                 [CallerMemberName] string propertyName = null)  
           {  
               if (EqualityComparer<T>.Default.Equals(  
                            backingField, value)) return;  
               backingField = value;  
               OnPropertyChanged(propertyName);  
           }  
       }  
   }  

Here is my xaml.

   <StackLayout>  
           <Button Text="exe" Command="{Binding TestCommand}"></Button>  
           <ActivityIndicator Grid.Row="1" Grid.Column="0" HeightRequest="100" WidthRequest="100" HorizontalOptions="Center" IsVisible="{Binding IsBusy}" IsRunning="True"/>  
     
       </StackLayout>  

Here is my layout's background code.

   public partial class MainPage : ContentPage  
       {  
           public MainPage()  
           {  
               InitializeComponent();  
               this.BindingContext = new MyViewModel();  
           }  
       }  

Best Regards,

Leon Lu

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