sharee.bike-App/SharedGui/View/BarLevelView.xaml.cs

using SharedGui.ViewModel;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace SharedGui.View
{
	[XamlCompilation(XamlCompilationOptions.Compile)]
	public partial class BarLevelView : ContentView
	{
		private BarLevelViewModel _LocalViewModel = new BarLevelViewModel();

		public BarLevelView()
		{
			InitializeComponent();

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

		/// <summary>
		/// Create bindable property to allow "Maximum"- property to act as a valid target for data binding.
		/// </summary>
		public static readonly BindableProperty MaximumProperty = BindableProperty.Create(
		   "Maximum",
		   typeof(string),
		   typeof(BarLevelView),
		   "", // Default value must match default value of view model object. Otherwise there might be an update issue.
		   propertyChanged: OnMaximumChanged);

		/// <summary>
		/// Holds the count of bars which 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 BarLevelView;
				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 allow "Current"- property to act as a valid target for data binding.
		/// </summary>
		public static readonly BindableProperty CurrentProperty = BindableProperty.Create(
		   "Current",
		   typeof(string),
		   typeof(BarLevelView),
		   "", // Default value must match default value of view model object. Otherwise there might be an update issue.
		   propertyChanged: OnCurrentChanged);

		/// <summary>
		/// Holds the count of bars which 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 BarLevelView;
				int current;
				batteryView?.SetCurrent(int.TryParse(newValue.ToString(), out current) ? (int?)current : null);
			}
		}

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