Change TextColor of Button on IsEnabled in Xamarin

Issue

In Xamarin App, I want to change the TextColor of Button when the IsEnabled = false. This button won't be enabled until on Item is selected from the Picker.

There is a solution by @Leo Zhu - MSFT => https://stackoverflow.com/a/64854260/14139029, which is very helpful, but it isn't working in this situation.

.xml

<Button
    x:Name="FormButton"
    IsEnabled="False"
    TextColor="#4DABFE"
    Text="Submit"
    Command={Binding FormButtonCommand}>
    <Button.Triggers>
        <MultiTrigger TargetType="Button">
             <MultiTrigger.Conditions>
                <BindingCondition Binding="{Binding SelectedState,
                                                       Converter={StaticResource stringNullOrEmptyValueBoolConverter }}" Value="false" />
                <BindingCondition Binding="{Binding SelectedCity,
                                                       Converter={StaticResource stringNullOrEmptyValueBoolConverter }}" Value="false" />
             </MultiTrigger.Conditions>

        <Setter Property="IsEnabled" Value="True" />
        </MultiTrigger>
    </Button.Triggers>
</Button>

ViewModel.cs

public ICommand FormButtonCommand => new Command(async (formbutton) =>
{
    if (SelectedCity == "Tokyo")
    {
        // Code
    }
    else if (SelectedCity == "Moscow")
    {
        // Code
    }
}, (x) => false);

Solution

Ok,it's the same reason,you set the Button's IsEnable property,when it's false,it will display with a default style.

Here is a solution for this case(it also applies to the last case)：

Create a custom ButtonRenderer in both platform:

For Android：

[assembly: ExportRenderer(typeof(Button), typeof(CustomButtonRenderer))]
namespace Your namepace
{
   class CustomButtonRenderer :ButtonRenderer
   {

      public CustomButtonRenderer(Context context):base(context)
      {

      } 
      protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
      {
         base.OnElementChanged(e);
         if (Control != null) SetColors();
   
      }

      protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs args)
      {
         base.OnElementPropertyChanged(sender, args);
         if (args.PropertyName == nameof(Button.IsEnabled)) SetColors();
      }
      private void SetColors()
      {
         Control.SetTextColor(Element.IsEnabled ? Color.FromHex("004B87").ToAndroid() : Color.FromHex("4DABFE").ToAndroid());
         Control.SetBackgroundColor(Element.IsEnabled ? Color.FromHex("222222").ToAndroid() : Color.FromHex("FFFFFF").ToAndroid());
      }
   }
}     

For ios:

[assembly: ExportRenderer(typeof(Button), typeof(CustomButtonRenderer))]
namespace Your namepace
{
  public class CustomButtonRenderer: ButtonRenderer
  {
    protected override void OnElementChanged(ElementChangedEventArgs<Button> args)
    {
        base.OnElementChanged(args);
        if (Control != null) SetColors();
    }

    protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs args)
    {
        base.OnElementPropertyChanged(sender, args);
        if (args.PropertyName == nameof(Button.IsEnabled)) SetColors();
    }

    private void SetColors()
    {
        Control.SetTitleColor(Element.IsEnabled ? Color.FromHex("004B87").ToUIColor() : Color.FromHex("4DABFE").ToUIColor(), Element.IsEnabled ? UIControlState.Normal : UIControlState.Disabled);
        Control.BackgroundColor = Element.IsEnabled ? Color.FromHex("222222").ToUIColor() : Color.FromHex("FFFFFF").ToUIColor();
    }
  }
}

Answered By - Leo Zhu - MSFT