sharee.bike-App/ShareeSharedGuiLib/View/BarLevelInputView.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using ShareeSharedGuiLib.ViewModel;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace ShareeSharedGuiLib.View
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class BarLevelInputView : ContentView
    {
        private BarLevelInputViewModel _LocalViewModel;

        public BarLevelInputView()
        {
            InitializeComponent();

            _LocalViewModel = new BarLevelInputViewModel();

            _LocalViewModel.PropertyChanged += (sender, args) =>
            {
                // Update Current property from view model on user input.
                if (args.PropertyName != nameof(BarLevelInputViewModel.Current))
                    return;

                var viewModel = sender as BarLevelInputViewModel;
                Current = viewModel?.Current != null
                    ? viewModel?.Current.Value.ToString()
                    : String.Empty;
            };

            // Do not bind entire control to local view model. Doing this would break binding of BatteryView control. 
            this.BarLevelElement.BindingContext = _LocalViewModel;
            this.BarLevelStepper.BindingContext = _LocalViewModel;
        }

        /// <summary>
        /// Create bindable property to to allow "Maximum"- proptery to act as a valid target for data binding.
        /// </summary>
        public static readonly BindableProperty MaximumProperty = BindableProperty.Create(
           "Maximum",
           typeof(string),
           typeof(BarLevelInputView),
           "7",
           propertyChanged: OnMaximumChanged);

        /// <summary>
        /// Holds the count of bars wich represent charing level full.
        /// </summary>
        public string Maximum
        {
            get => (string)GetValue(MaximumProperty);
            set => SetValue(MaximumProperty, value);
        }

        /// <summary>
        /// Notifies when value changes. Is required to make binding work.
        /// </summary>
        static void OnMaximumChanged(BindableObject bindable, object oldValue, object newValue)
        {
            if (newValue != oldValue)
            {
                var batteryView = bindable as BarLevelInputView;
                batteryView?.SetMaximum(int.TryParse(newValue.ToString(), out int maximum) ? (int?)maximum : null);
            }
        }

        public void SetMaximum(int? maximum) => _LocalViewModel.Maximum = maximum;


        /// <summary>
        /// Create bindable property to to allow "Current"- proptery to act as a valid target for data binding.
        /// </summary>
        public static readonly BindableProperty CurrentProperty = BindableProperty.Create(
           "Current",
           typeof(string),
           typeof(BarLevelInputView),
           "7",
           BindingMode.TwoWay,
           propertyChanged: OnCurrentChanged);

        /// <summary>
        /// Holds the count of bars wich represent the current charing level.
        /// </summary>
        public string Current
        {
            get => (string)GetValue(CurrentProperty);
            set => SetValue(CurrentProperty, value);
        }

        /// <summary>
        /// Notifies when value changes. Is required to make binding work.
        /// </summary>
        static void OnCurrentChanged(BindableObject bindable, object oldValue, object newValue)
        {
            if (newValue != oldValue)
            {
                var batteryView = bindable as BarLevelInputView;
                int current;
                batteryView?.SetCurrent(int.TryParse(newValue.ToString(), out current) ? (int?)current : null);
            }
        }

        public void SetCurrent(int? current) => _LocalViewModel.Current = current;

    }
}