How can I change the color of a label depending on if isEnabled is true or false?

Issue

I have this code in a template that I am using, but it’s not able to work because of this message:

ErrorMessage

I understand why the message is present but I do not know how to fix this so that the label color depends on the state of the isEnabled.

namespace Templates
{
    public class LinkLabel : Label
    {
        public LinkLabel()
        {
            this.SetDynamicResource(Label.FontFamilyProperty, "Default-Regular");
            this.SetDynamicResource(Label.FontSizeProperty,   "LabelTextFontSize");
            this.SetDynamicResource(Label.TextColorProperty,  "LinkLabelColor");
            VerticalTextAlignment  TextAlignment.Center;
            VerticalOptions  LayoutOptions.CenterAndExpand;
        }

        public static BindableProperty IsEnabledProperty 
    BindableProperty.Create(nameof(IsDisabled), typeof(bool), typeof(LinkLabel), default(bool), propertyChanged: IsEnabledPropertyPropertyChanged);

        public bool IsDisabled
        {
            get { return (bool)GetValue(IsEnabledProperty); }
            set { SetValue(IsEnabledProperty, value); }
        }

        private static void IsEnabledPropertyPropertyChanged(BindableObject bindable, object oldValue, object newValue)
        {
            if ((bool)newValue)
            {
                LinkLabel label  bindable as LinkLabel;
                label.SetDynamicResource(Label.TextColorProperty, "LinkLabelDisabledColor");
            }
            else
            {
                LinkLabel label  bindable as LinkLabel;
                label.SetDynamicResource(Label.TextColorProperty, "LinkLabelColor");
            }
        }
    }
}

Solution

If we check the source code of class VisualElement , we will find that there is already a bindable property called IsEnabledProperty . As VisualElement is the super class of most of UI Elements . So there will be ambiguity between the two IsEnabledProperty .

enter image description here

Solution 1:

The easiest way is modify the name of the bindable property like IsDisabledProperty

Solution 2:

Since there is already a IsEnabledProperty in the Label . We could set the value in xaml and handle the logic in code behind like

public class LinkLabel : Label
{
    public LinkLabel()
    {
        this.SetDynamicResource(Label.FontFamilyProperty, "Default-Regular");
        this.SetDynamicResource(Label.FontSizeProperty, "LabelTextFontSize");
        this.SetDynamicResource(Label.TextColorProperty, "LinkLabelColor");
        VerticalTextAlignment  TextAlignment.Center;
        VerticalOptions  LayoutOptions.CenterAndExpand;

        this.PropertyChanged + LinkLabel_PropertyChanged;

    }

    private void LinkLabel_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {

        if(e.PropertyName "IsEnabled")
        {
            var label  sender as LinkLabel;
            var newValue  label.IsEnabled;

            if ((bool)newValue)
            {

                this.SetDynamicResource(Label.TextColorProperty, "LinkLabelDisabledColor");
            }
            else
            {

                this.SetDynamicResource(Label.TextColorProperty, "LinkLabelColor");
            }

        }

    }

Answered By – Lucas Zhang – MSFT

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