How to add binding property to Label with converter BoolToObjectConverter

Question

I've the next converter code like the example in this post Xamarin.Forms Binding Converter
but when the value come in method only have the property Path="DeviceHasScanner" and the Binding property never is called :(

public class BoolToObjectConverter<T> : IValueConverter  
    {  
       public T TrueObject { set; get; }  
  
       public T FalseObject { set; get; }  
  
       public object Convert(object value, Type targetType, object parameter, CultureInfo culture)  
       {  
           return (bool)value ? TrueObject : FalseObject;  
       }  
  
       public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)  
       {  
           return ((T)value).Equals(TrueObject);  
       }  
   }  

And I'm try implement it on this way:

<Image HorizontalOptions="Center" WidthRequest="200">  
     <Image.Source>  
         <Binding Source="{Binding DeviceHasScanner}">  
               <Binding.Converter>  
                     <converters:BoolToObjectConverter x:TypeArguments="x:String"  TrueObject="presstoscan.png" FalseObject="scanwithcamera.png" />  
                </Binding.Converter>  
          </Binding>  
     </Image.Source>  
 </Image>  
  

And the boolean binding property in viewmodel is it but never is called:

public bool DeviceHasScanner  
    {  
        get   
        {  
            return Settings.Get.DeviceHasScanner; //This code return true or false  
        }  
 }  

What is the correct way to implement it?

Answer 1

Hello,

The Value Convertor will get value from the property value of Path.

For instance:

   <Binding Source="{RelativeSource Self}"  
            Path="WidthRequest">  

If you set WidthRequest to Path, you will find the value of converter is 200.

Therefore, you need to set a new property into Image to bind DeviceHasScanner as the following code:

   public class MyImage : Image  
   {  
       public static readonly BindableProperty DeviceHasScannerProperty =  
   BindableProperty.Create("DeviceHasScanner", typeof(bool), typeof(MyImage), null);  
       public bool DeviceHasScanner  
       {  
           get { return (bool)GetValue(DeviceHasScannerProperty); }  
           set { SetValue(DeviceHasScannerProperty, value); }  
       }  
   }  

In XAML:

   <converters:MyImage x:Name="img" HorizontalOptions="Center" WidthRequest="200" DeviceHasScanner="{Binding DeviceHasScanner}">  
   ...  
   <Binding Source="{RelativeSource Self}"  
            Path="DeviceHasScanner">  

Best Regards,

Alec Liu.

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