Disabled button style on iOS in Xamarin.Forms

All the credits for solution described in this post goes my friend qbus. He saved few hours of my life and my sanity ;-)

In Xamarin.Forms application I have a button with non-default styling (defined in XAML). Target platforms are iOS and Android. Enabled and disabled states should obviously be distinguished with colors.

The most straightforward solution that makes use of Data Triggers works well for Android. For some reason it doesn’t want to work properly on iOS. If the button is initially disabled it displays correctly in this state but after changing IsEnabled to true and then back to false it does not anymore. Interestingly the background taken from style setter is good, but not the text color property. It turns out to be set to some awkward value: rgb(123, 123, 123) with alpha 89. I guess this is the default value for disabled state because it’s not defined anywhere in the app.

The problem is well described on the Xamarin Forum thread. Unfortunately none of the proposed workarounds worked for me.

The initial workaround implemented by the previous developer was implementing a custom renderer. In OnElementChanged(ElementChangedEventArgs<Button>) the button’s title color was set for UIControlState.Disabled state. For some weird reason this was working only for the initial disable state (as described above). The second solution, proposed by my friend, is using the NSAttributedString set as entire button title:

public class ButtonDisabledTextColorRenderer : ButtonRenderer
{
    private static UIColor DisabledColor => Color.FromHex("#FFFFFF").ToUIColor();

    protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
    {
        base.OnElementChanged(e);

        if (Control == null)
            return;

        var title = new NSAttributedString(Control.CurrentTitle, new UIStringAttributes {ForegroundColor = DisabledColor});
        Control.SetAttributedTitle(title, UIControlState.Disabled);
    }
}

I should call this rather workaround than the real clean solution. Xamarin.Forms obviously has some bug in this case. Nevertheless it works.

Happy coding!