Xamarin Forms Custom Stepper with 2 buttons and Entry

Question

I implemented this CustomStepper:

 using System;
    using Xamarin.Forms;

    namespace AppXamarin
    {
        public class CustomStepper : StackLayout
        {

            Button PlusBtn;
            Button MinusBtn;
            Entry Entry;

            public static readonly BindableProperty TextProperty =
              BindableProperty.Create(
                 propertyName: "Text",
                  returnType: typeof(int),
                  declaringType: typeof(CustomStepper),
                  defaultValue: 0,
                  defaultBindingMode: BindingMode.TwoWay);

            public int Text
            {
                get { return (int)GetValue(TextProperty); }
                set { SetValue(TextProperty, value); }
            }
            public CustomStepper()
            {
                PlusBtn = new Button { WidthRequest = 30, HeightRequest = 30 };
                MinusBtn = new Button { WidthRequest = 30, HeightRequest = 30 };
                PlusBtn.Image = "exp20181029Artboard51";
                MinusBtn.Image = "exp20181029Artboard52";
                switch (Device.RuntimePlatform)
                {
                    case Device.UWP:
                    case Device.Android:
                        {
                            PlusBtn.BackgroundColor = Color.Transparent;
                            MinusBtn.BackgroundColor = Color.Transparent;
                            break;
                        }
                    case Device.iOS:
                        {
                            PlusBtn.BackgroundColor = Color.Transparent;
                            MinusBtn.BackgroundColor = Color.Transparent;
                            break;
                        }
                }
                Orientation = StackOrientation.Horizontal;
                PlusBtn.Clicked += PlusBtn_Clicked;
                MinusBtn.Clicked += MinusBtn_Clicked;
                Entry = new Entry { PlaceholderColor = Color.Gray, Keyboard = Keyboard.Numeric, WidthRequest = 30, BackgroundColor = Color.Transparent, FontSize = 15 };
                Entry.Keyboard = Keyboard.Numeric;
                Entry.Behaviors.Add(new NumericValidationBehavior());
                Entry.SetBinding(Entry.TextProperty, new Binding(nameof(Text), BindingMode.TwoWay, source: this));
                Entry.HorizontalTextAlignment = TextAlignment.Center;
                Entry.TextChanged += Entry_TextChanged;
                Children.Add(MinusBtn);
                Children.Add(Entry);
                Children.Add(PlusBtn);
            }
            private void Entry_TextChanged(object sender, TextChangedEventArgs e)
            {
                if (!string.IsNullOrEmpty(e.NewTextValue) && e.NewTextValue != ".")
                    this.Text = int.Parse(e.NewTextValue);
            }

            private void MinusBtn_Clicked(object sender, EventArgs e)
            {
                if (Text > 0)
                    Text--;
            }

            private void PlusBtn_Clicked(object sender, EventArgs e)
            {
                Text++;
            }

        }
    }

When placing normally in the page I can access it and take the text property and use it in my Xaml.cs code. But in my case, I'm placing it inside a listview and as you know in listview the items are bindable I can't access it directly. In the regular stepper when it is placed in the listview we can use the "ValueChanged" method and can easily get the value by using e.NewValue in the "ValueChanged" method in the Xaml.cs file. Is there a way that I can add something to the CustomStepper class that can help me access the Text property and uses it in the Xaml.cs file? Thanks in advance

Answer 1

You can create a property for EventHandlers. In this case, you would use the event modifier on the property to tell the program that the property is triggering an event. For example:

private EventHandler onValueChangedEvent = null;

public event EventHandler OnValueChanged
{
    add
    {
        onValueChangedEvent = null;
        onValueChangedEvent = value;
    }
    remove
    {
        // Will show a warning. You can ignore it.
        onValueChangedEvent = null;
    }
}

private void Entry_TextChanged(object sender, TextChangedEventArgs e)
{
    if (!string.IsNullOrEmpty(e.NewTextValue) && e.NewTextValue != ".")
        this.Text = int.Parse(e.NewTextValue);

    onValueChangedEvent?.Invoke(this, e);
}

You would then bind/assign an event handler in your xaml.cs code to the OnValueChanged property, which will get triggered when the value changes.