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;

	}
}